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Tyszkiewicz C, Hwang SK, Manickam B, Jakubczak B, Walters KM, Bolt MW, Santos R, Liu CN. Sex-related differences in retinal function in Wistar rats: implications for toxicity and safety studies. FRONTIERS IN TOXICOLOGY 2023; 5:1176665. [PMID: 37313214 PMCID: PMC10259507 DOI: 10.3389/ftox.2023.1176665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 05/10/2023] [Indexed: 06/15/2023] Open
Abstract
Introduction: Wistar Han rats are a preferred strain of rodents for general toxicology and safety pharmacology studies in drug development. In some of these studies, visual functional tests that assess for retinal toxicity are included as an additional endpoint. Although the influence of gender on human retinal function has been documented for more than 6 decades, preclinically it is still uncertain if there are differences in retinal function between naïve male and female Wistar Han rats. Methods: In this study, sex-related differences in the retinal function were quantified by analyzing electroretinography (ERG) in 7-9-week-old (n = 52 males and 51 females) and 21-23-week-old Wistar Han rats (n = 48 males and 51 females). Optokinetic tracking response, brainstem auditory evoked potential, ultrasonic vocalization and histology were tested and evaluated in a subset of animals to investigate the potential compensation mechanisms of spontaneous blindness. Results/Discussion: Absence of scotopic and photopic ERG responses was found in 13% of 7-9-week-old (7/52) and 19% of 21-23-week-old males (9/48), but none of female rats (0/51). The averaged amplitudes of rod- and cone-mediated ERG b-wave responses obtained from males were significantly smaller than the amplitudes of the same responses from age-matched females (-43% and -26%, respectively) at 7-9 weeks of age. There was no difference in the retinal and brain morphology, brainstem auditory responses, or ultrasonic vocalizations between the animals with normal and abnormal ERGs at 21-23 weeks of age. In summary, male Wistar Han rats had altered retinal responses, including a complete lack of responses to test flash stimuli (i.e., blindness), when compared with female rats at 7-9 and 21-23 weeks of age. Therefore, sex differences should be considered when using Wistar Han rats in toxicity and safety pharmacology studies with regards to data interpretation of retinal functional assessments.
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Affiliation(s)
| | | | | | - Ben Jakubczak
- Comparative Medicine, Pfizer, Groton, CT, United States
| | - Karen M. Walters
- Drug Safety Research and Development, Pfizer, Groton, CT, United States
| | - Michael W. Bolt
- Drug Safety Research and Development, Pfizer, Cambridge, Massachusetts, United States
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2
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Jacobs PJ, Oosthuizen MK. Laterality in the Damaraland Mole-Rat: Insights from a Eusocial Mammal. Animals (Basel) 2023; 13:ani13040627. [PMID: 36830415 PMCID: PMC9951763 DOI: 10.3390/ani13040627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 02/07/2023] [Accepted: 02/08/2023] [Indexed: 02/15/2023] Open
Abstract
Lateralization is the functional control of certain behaviors in the brain being processed by either the left or right hemisphere. Behavioral asymmetries can occur at an individual and population level, although population-level lateralization is less common amongst solitary species, whereas social species can benefit more from aligning and coordinating their activities. We assessed laterality (individual and population) through turning biases in the eusocial Damaraland mole rat, Fukomys damarensis. We considered factors such as breeding status (queen or subordinate), environment (wild-caught or captive), sex (male or female), colony and body mass. All individuals together demonstrated significant left-turning biases, which was also significant at the population level. Wild-caught animals were more strongly lateralized, had a wider spread over a laterality index and lacked the population-level left-turning bias as compared to captive mole rats. Subordinate animals were more lateralized than queens, demonstrating social status differences in turning biases for social mole rats. This emphasizes the importance of animal handling and context when measuring and interpreting behavioral asymmetries.
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Affiliation(s)
- Paul J. Jacobs
- Department of Zoology & Entomology, University of Pretoria, Private Bag X20, Pretoria 0028, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
- Correspondence:
| | - Maria K. Oosthuizen
- Department of Zoology & Entomology, University of Pretoria, Private Bag X20, Pretoria 0028, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
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3
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Hite NJ, Sudheimer KD, Anderson L, Sarko DK. Spatial Learning and Memory in the Naked Mole-Rat: Evolutionary Adaptations to a Subterranean Niche. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.879989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Evolutionary adaptation to a subterranean habitat consisting of extensive underground tunnel systems would presumably require adept spatial learning and memory, however, such capabilities have not been characterized to date in naked mole-rats (Heterocephalus glaber) which, like other members of Bathyergidae, are subterranean rodents. The goal of this study was to develop a method for effectively assessing spatial learning and memory by modifying a Hebb-Williams maze for use with these subterranean rodents. Established behavioral tests to assess spatial learning and memory have primarily focused on, and have been optimized for, more typical laboratory rodent species such as mice and rats. In the current study, we utilized species-appropriate motivators, analyzed learning curves associated with maze performance, and tested memory retention in naked mole-rats. Using a modified Hebb-Williams maze, naked mole-rats underwent 3 days of training, consisting of five trials per day wherein they could freely explore the maze in search of the reward chamber. Memory retention was then tested 1 day, 1 week, and 1 month following the last day of training. Performance was analyzed based on latency to the reward chamber, errors made, and distance traveled to reach the reward chamber. Overall, this study established a behavioral paradigm for assessing maze navigation, spatial learning, and spatial memory in subterranean rodents, including optimization of rewards and environmental motivators.
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4
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Buffenstein R, Amoroso V, Andziak B, Avdieiev S, Azpurua J, Barker AJ, Bennett NC, Brieño‐Enríquez MA, Bronner GN, Coen C, Delaney MA, Dengler‐Crish CM, Edrey YH, Faulkes CG, Frankel D, Friedlander G, Gibney PA, Gorbunova V, Hine C, Holmes MM, Jarvis JUM, Kawamura Y, Kutsukake N, Kenyon C, Khaled WT, Kikusui T, Kissil J, Lagestee S, Larson J, Lauer A, Lavrenchenko LA, Lee A, Levitt JB, Lewin GR, Lewis Hardell KN, Lin TD, Mason MJ, McCloskey D, McMahon M, Miura K, Mogi K, Narayan V, O'Connor TP, Okanoya K, O'Riain MJ, Park TJ, Place NJ, Podshivalova K, Pamenter ME, Pyott SJ, Reznick J, Ruby JG, Salmon AB, Santos‐Sacchi J, Sarko DK, Seluanov A, Shepard A, Smith M, Storey KB, Tian X, Vice EN, Viltard M, Watarai A, Wywial E, Yamakawa M, Zemlemerova ED, Zions M, Smith ESJ. The naked truth: a comprehensive clarification and classification of current 'myths' in naked mole-rat biology. Biol Rev Camb Philos Soc 2022; 97:115-140. [PMID: 34476892 PMCID: PMC9277573 DOI: 10.1111/brv.12791] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 12/17/2022]
Abstract
The naked mole-rat (Heterocephalus glaber) has fascinated zoologists for at least half a century. It has also generated considerable biomedical interest not only because of its extraordinary longevity, but also because of unusual protective features (e.g. its tolerance of variable oxygen availability), which may be pertinent to several human disease states, including ischemia/reperfusion injury and neurodegeneration. A recent article entitled 'Surprisingly long survival of premature conclusions about naked mole-rat biology' described 28 'myths' which, those authors claimed, are a 'perpetuation of beautiful, but falsified, hypotheses' and impede our understanding of this enigmatic mammal. Here, we re-examine each of these 'myths' based on evidence published in the scientific literature. Following Braude et al., we argue that these 'myths' fall into four main categories: (i) 'myths' that would be better described as oversimplifications, some of which persist solely in the popular press; (ii) 'myths' that are based on incomplete understanding, where more evidence is clearly needed; (iii) 'myths' where the accumulation of evidence over the years has led to a revision in interpretation, but where there is no significant disagreement among scientists currently working in the field; (iv) 'myths' where there is a genuine difference in opinion among active researchers, based on alternative interpretations of the available evidence. The term 'myth' is particularly inappropriate when applied to competing, evidence-based hypotheses, which form part of the normal evolution of scientific knowledge. Here, we provide a comprehensive critical review of naked mole-rat biology and attempt to clarify some of these misconceptions.
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Affiliation(s)
| | - Vincent Amoroso
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Blazej Andziak
- Graduate Center City University of New York365 Fifth AvenueNew YorkNY10016U.S.A.
| | | | - Jorge Azpurua
- Department of AnesthesiologyStony Brook University101 Nicolls RoadStony BrookNY11794U.S.A.
| | - Alison J. Barker
- Max Delbrück Center for Molecular MedicineRobert‐Rössle‐Str 10Berlin‐Buch13092Germany
| | - Nigel C. Bennett
- Mammal Research Institute, Department of Zoology and EntomologyUniversity of PretoriaPretoria0002South Africa
| | - Miguel A. Brieño‐Enríquez
- Department of Obstetrics, Gynecology & Reproductive MedicineMagee‐Womens Research Institute204 Craft AvenuePittsburghPA15213U.S.A.
| | - Gary N. Bronner
- Department Biological SciencesRondeboschCape Town7701South Africa
| | - Clive Coen
- Reproductive Neurobiology, Division of Women's HealthSchool of Medicine, King's College LondonWestminster Bridge RoadLondonSE1 7EHU.K.
| | - Martha A. Delaney
- Zoological Pathology ProgramUniversity of Illinois3505 Veterinary Medicine Basic Sciences Building, 2001 S Lincoln AvenueUrbanaIL6180U.S.A.
| | - Christine M. Dengler‐Crish
- Department of Pharmaceutical SciencesNortheast Ohio Medical University4209 State Route 44RootstownOH44272U.S.A.
| | - Yael H. Edrey
- Northwest Vista College3535 N. Ellison DriveSan AntonioTX78251U.S.A.
| | - Chris G. Faulkes
- School of Biological and Chemical SciencesQueen Mary University of LondonMile End RoadLondonE1 4NSU.K.
| | - Daniel Frankel
- School of EngineeringNewcastle UniversityMerz CourtNewcastle Upon TyneNE1 7RUU.K.
| | - Gerard Friedlander
- Université Paris DescartesFaculté de Médecine12 Rue de l'École de MédecineParis5006France
| | - Patrick A. Gibney
- Cornell University College of Veterinary MedicineIthacaNY14853U.S.A.
| | - Vera Gorbunova
- Departments of BiologyUniversity of Rochester402 Hutchison HallRochesterNY14627U.S.A.
| | - Christopher Hine
- Cleveland ClinicLerner Research Institute9500 Euclid AvenueClevelandOH44195U.S.A.
| | - Melissa M. Holmes
- Department of PsychologyUniversity of Toronto Mississauga3359 Mississauga Road NorthMississaugaONL5L 1C6Canada
| | | | - Yoshimi Kawamura
- Department of Aging and Longevity ResearchKumamoto University1‐1‐1 HonjoKumamoto860‐0811Japan
| | - Nobuyuki Kutsukake
- Department of Evolutionary Studies of BiosystemsThe Graduate University for Advanced StudiesHayama240‐0193Japan
| | - Cynthia Kenyon
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Walid T. Khaled
- The School of the Biological SciencesUniversity of CambridgeTennis Court RoadCambridgeCB2 1PDU.K.
| | - Takefumi Kikusui
- Companion Animal Research, School of Veterinary MedicineAzabu UniversitySagamihara252‐5201Japan
| | - Joseph Kissil
- Department of Cancer BiologyThe Scripps Research InstituteScripps FloridaJupiterFL33458U.S.A.
| | - Samantha Lagestee
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - John Larson
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Amanda Lauer
- Department of OtolaryngologyJohns Hopkins School of MedicineBaltimoreMD21205U.S.A.
| | - Leonid A. Lavrenchenko
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesLeninskii pr. 33Moscow119071Russia
| | - Angela Lee
- Graduate Center City University of New York365 Fifth AvenueNew YorkNY10016U.S.A.
| | - Jonathan B. Levitt
- Biology DepartmentThe City College of New York138th Street and Convent AvenueNew YorkNY10031U.S.A.
| | - Gary R. Lewin
- Max Delbrück Center for Molecular MedicineRobert‐Rössle‐Str 10Berlin‐Buch13092Germany
| | | | - TzuHua D. Lin
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Matthew J. Mason
- The School of the Biological SciencesUniversity of CambridgeTennis Court RoadCambridgeCB2 1PDU.K.
| | - Dan McCloskey
- College of Staten Island in the City University of New York2800 Victory BlvdStaten IslandNY10314U.S.A.
| | - Mary McMahon
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Kyoko Miura
- Department of Aging and Longevity ResearchKumamoto University1‐1‐1 HonjoKumamoto860‐0811Japan
| | - Kazutaka Mogi
- Companion Animal Research, School of Veterinary MedicineAzabu UniversitySagamihara252‐5201Japan
| | - Vikram Narayan
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | | | - Kazuo Okanoya
- Department of Life SciencesThe University of Tokyo7‐3‐1 HongoTokyo153‐8902Japan
| | | | - Thomas J. Park
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Ned J. Place
- Cornell University College of Veterinary MedicineIthacaNY14853U.S.A.
| | - Katie Podshivalova
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | | | - Sonja J. Pyott
- Groningen Department of OtorhinolaryngologyUniversity Medical CenterPostbus 30.001GroningenRB9700The Netherlands
| | - Jane Reznick
- Cologne Excellence Cluster for Cellular Stress Responses in Aging‐Associated Diseases (CECAD)University Hospital CologneJoseph‐Stelzmann‐Street 26Cologne50931Germany
| | - J. Graham Ruby
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Adam B. Salmon
- Barshop Institute for Longevity and Aging StudiesUniversity of Texas Health Science Center4939 Charles Katz Dr.San AntonioTX78229U.S.A.
| | - Joseph Santos‐Sacchi
- Department of NeuroscienceYale University School of Medicine200 South Frontage Road, SHM C‐303New HavenCT06510U.S.A.
| | - Diana K. Sarko
- Department of AnatomySchool of Medicine, Southern Illinois University975 S. NormalCarbondaleIL62901U.S.A.
| | - Andrei Seluanov
- Departments of BiologyUniversity of Rochester402 Hutchison HallRochesterNY14627U.S.A.
| | - Alyssa Shepard
- Department of Cancer BiologyThe Scripps Research InstituteScripps FloridaJupiterFL33458U.S.A.
| | - Megan Smith
- Calico Life Sciences LLC1170 Veterans BlvdSouth San FranciscoCA94080U.S.A.
| | - Kenneth B. Storey
- Department of BiologyCarleton University1125 Colonel By DriveOttawaONK1S 5B6Canada
| | - Xiao Tian
- Department of Genetics – Blavatnik InstituteHarvard Medical School77 Avenue Louis PasteurBostonMA02115U.S.A.
| | - Emily N. Vice
- Department of Biological SciencesUniversity of Illinois at ChicagoChicagoIL60607U.S.A.
| | - Mélanie Viltard
- Fondation pour la recherche en PhysiologieUniversité Catholique de LouvainClos Chapelle‐aux‐Champs 30Woluwe‐saint Lambert1200Belgium
| | - Akiyuki Watarai
- Companion Animal Research, School of Veterinary MedicineAzabu UniversitySagamihara252‐5201Japan
| | - Ewa Wywial
- Biology DepartmentThe City College of New York138th Street and Convent AvenueNew YorkNY10031U.S.A.
| | - Masanori Yamakawa
- Department of Evolutionary Studies of BiosystemsThe Graduate University for Advanced StudiesHayama240‐0193Japan
| | - Elena D. Zemlemerova
- A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesLeninskii pr. 33Moscow119071Russia
| | - Michael Zions
- Graduate Center City University of New York365 Fifth AvenueNew YorkNY10016U.S.A.
| | - Ewan St. John Smith
- The School of the Biological SciencesUniversity of CambridgeTennis Court RoadCambridgeCB2 1PDU.K.
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5
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Cooper TK, Meyerholz DK, Beck AP, Delaney MA, Piersigilli A, Southard TL, Brayton CF. Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits. ILAR J 2022; 62:77-132. [PMID: 34979559 DOI: 10.1093/ilar/ilab022] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/12/2021] [Indexed: 12/31/2022] Open
Abstract
Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.
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Affiliation(s)
- Timothy K Cooper
- Department of Comparative Medicine, Penn State Hershey Medical Center, Hershey, PA, USA
| | - David K Meyerholz
- Department of Pathology, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa, USA
| | - Amanda P Beck
- Department of Pathology, Yeshiva University Albert Einstein College of Medicine, Bronx, New York, USA
| | - Martha A Delaney
- Zoological Pathology Program, University of Illinois at Urbana-Champaign College of Veterinary Medicine, Urbana-Champaign, Illinois, USA
| | - Alessandra Piersigilli
- Laboratory of Comparative Pathology and the Genetically Modified Animal Phenotyping Service, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Teresa L Southard
- Department of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York, USA
| | - Cory F Brayton
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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6
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Vice EN, Lagestee S, Browe BM, Deb D, Smith ESJ, Park TJ. Sensory Systems of the African Naked Mole-Rat. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:137-156. [PMID: 34424515 DOI: 10.1007/978-3-030-65943-1_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Naked mole-rats share some sensory characteristics with other subterraneans, including lack of object vision, retention of the ability to entrain their circadian rhythm to light, and poor hearing. On the other hand, a characteristic that may be specialized in the naked mole-rat is their exquisite orienting responses to the touch of even a single body vibrissa. They have about 100 whisker-like body vibrissae on their otherwise furless bodies. They are also insensitive to chemical and inflammatory pain, likely an adaptation to living in an atmosphere that is high in carbon dioxide, a result of many respiring individuals driving carbon dioxide accumulation. Naked mole-rats have the highest population density among subterranean mammals. High levels of carbon dioxide cause tissue acidosis and associated pain. Remarkably, naked mole-rats are completely immune to carbon dioxide-induced pulmonary edema. However, they retain the ability to detect acid as a taste (sour). Finally, their ability to smell and discriminate odors is comparable to that of rats and mice, but their vomeronasal organ, associated with sensing pheromones, is extremely small and shows a complete lack of post-natal growth. In this chapter, we review what is known about the sensory systems of the naked mole-rat with emphasis on how they differ from other mammals, and even other subterraneans. More extensive accounts of the naked mole-rat's auditory and pain systems can be found in other chapters of this book.
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Affiliation(s)
- Emily N Vice
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Samantha Lagestee
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Brigitte M Browe
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Deblina Deb
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA.,Kids In Motion Pediatric Therapy Services, Highland, MI, USA
| | - Ewan St J Smith
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Thomas J Park
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA.
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7
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Roscito JG, Subramanian K, Naumann R, Sarov M, Shevchenko A, Bogdanova A, Kurth T, Foerster L, Kreysing M, Hiller M. Recapitulating Evolutionary Divergence in a Single Cis-Regulatory Element Is Sufficient to Cause Expression Changes of the Lens Gene Tdrd7. Mol Biol Evol 2021; 38:380-392. [PMID: 32853335 PMCID: PMC7826196 DOI: 10.1093/molbev/msaa212] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Mutations in cis-regulatory elements play important roles for phenotypic changes during evolution. Eye degeneration in the blind mole rat (BMR; Nannospalax galili) and other subterranean mammals is significantly associated with widespread divergence of eye regulatory elements, but the effect of these regulatory mutations on eye development and function has not been explored. Here, we investigate the effect of mutations observed in the BMR sequence of a conserved noncoding element upstream of Tdrd7, a pleiotropic gene required for lens development and spermatogenesis. We first show that this conserved element is a transcriptional repressor in lens cells and that the BMR sequence partially lost repressor activity. Next, we recapitulated evolutionary changes in this element by precisely replacing the endogenous regulatory element in a mouse line by the orthologous BMR sequence with CRISPR-Cas9. Strikingly, this repressor replacement caused a more than 2-fold upregulation of Tdrd7 in the developing lens; however, increased mRNA level does not result in a corresponding increase in TDRD7 protein nor an obvious lens phenotype, possibly explained by buffering at the posttranscriptional level. Our results are consistent with eye degeneration in subterranean mammals having a polygenic basis where many small-effect mutations in different eye-regulatory elements collectively contribute to phenotypic differences.
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Affiliation(s)
- Juliana G Roscito
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Kaushikaram Subramanian
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Ronald Naumann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Mihail Sarov
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Anna Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Aliona Bogdanova
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering, Technology Platform, TU, Dresden, Germany
| | - Leo Foerster
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Moritz Kreysing
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology, Dresden, Germany.,Center of Excellence, Physics of Life, Technical University, Dresden, Germany
| | - Michael Hiller
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
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8
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Finn KT. Potential use of a magnetic compass during long-distance dispersal in a subterranean rodent. J Mammal 2021. [DOI: 10.1093/jmammal/gyaa163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Abstract
Geomagnetic sensitivity is present in a variety of vertebrates, but only recently has attention focused on subterranean mammals. We report the potential use of a magnetic compass in wild Damaraland mole-rats (Fukomys damarensis) during dispersal at two sites in the Kalahari region of South Africa. When the distance traveled was greater than 250 m, males and females dispersed in opposite directions and females preferentially chose a predominantly northeastern direction. This directional choice likely is due to the differing dispersal tactics between sexes. This evidence suggests that Damaraland mole-rats employ a magnetic compass during aboveground dispersal to assist in locating mates or a new territory. This study provides evidence to show how magnetic compass use could be useful in dispersal, an important ecological process for mammals.
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Affiliation(s)
- Kyle T Finn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
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9
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Social Behavior in Naked Mole-Rats: Individual Differences in Phenotype and Proximate Mechanisms of Mammalian Eusociality. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:35-58. [PMID: 34424512 DOI: 10.1007/978-3-030-65943-1_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Naked mole-rats (Heterocephalus glaber) are small rodents native to east Africa, living in subterranean colonies of up to 300 individuals. Within each colony, reproduction is restricted to a single breeding female and 1-3 breeding males; all other colony members are reproductively suppressed and socially subordinate unless removed from the suppressive cues of the colony. Due to their striking reproductive skew, naked mole-rats are often considered eusocial mammals. Consistent with this idea, there are behavioral specializations and at least some evidence for morphological distinctions within and between the breeding and non-breeding members of the colony. Importantly, naked mole-rats show plasticity in their behavioral phenotype whereby changes in the social environment influence expression of both type and amount of social behavior. Thus, naked mole-rats provide the opportunity to examine the proximate mechanisms controlling individual differences in social behavior, shedding light on how mammals live in complex social groups.
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10
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Smith M, Buffenstein R. Managed Care of Naked Mole-Rats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:381-407. [PMID: 34424526 DOI: 10.1007/978-3-030-65943-1_16] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Naked mole-rats are a burgeoning model species in the field of biomedical research and are also housed at many zoos throughout the world. These mammals possess many traits that have a large impact on the way that they are kept in captivity such as their eusociality, thermolability and lack of need for drinking water. This chapter outlines the captive care and unusual housing needs of these animals. Providing information and examples from our own experiences while working with naked mole-rats for many decades. While this chapter serves as a good framework for the captive care of this mammal species, it is in no way all-encompassing but simply reflects the way in which we have managed over many years to successfully sustain our colony of thousands of animals.
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Affiliation(s)
- Megan Smith
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | - Rochelle Buffenstein
- Calico Life Sciences LLC, South San Francisco, CA, USA.
- Department of Pharmacology, University of Texas Health at San Antonio, San Antonio, TX, USA.
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11
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Delaney MA, Imai DM, Buffenstein R. Spontaneous Disease and Pathology of Naked Mole-Rats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1319:353-380. [PMID: 34424525 DOI: 10.1007/978-3-030-65943-1_15] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Naked mole-rats are highly valuable research models and popular exhibition animals at zoos worldwide. Here, we provide comprehensive descriptions of common postmortem findings of naked mole-rats from both research colonies and populations managed in zoological institutions. Included are brief reviews of their natural history and related physiologic adaptations, unique anatomical features, gross and histologic lesions of common as well as rarely reported disease processes, and discussions of possible pathogeneses with recommendations for future investigations to fill knowledge gaps. Based on postmortem data of several hundreds of naked mole-rats in managed care, it is clear that cancer is extremely rare and infectious disease is infrequently reported. However, despite relatively benign aging phenotypes in this species, several degenerative processes have been nevertheless observed in older populations of naked mole-rats. As such, some potential diet and husbandry-related issues are discussed in addition to the one of the most prominent causes of morbidity and mortality, conspecific aggression and traumas. From this review of lesions and disease, it is clear that pathology, including histopathology, is integral to better understanding mechanisms of healthy aging and cancer resistance of these extraordinary rodents.
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Affiliation(s)
- Martha A Delaney
- Zoological Pathology Program, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
| | - Denise M Imai
- Comparative Pathology Laboratory, School of Veterinary Medicine, University of California at Davis, Davis, CA, USA
| | - Rochelle Buffenstein
- Calico Life Sciences LLC, South San Francisco, CA, USA. .,Department of Pharmacology, University of Texas Health at San Antonio, San Antonio, TX, USA.
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12
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Braude S, Holtze S, Begall S, Brenmoehl J, Burda H, Dammann P, Marmol D, Gorshkova E, Henning Y, Hoeflich A, Höhn A, Jung T, Hamo D, Sahm A, Shebzukhov Y, Šumbera R, Miwa S, Vyssokikh MY, Zglinicki T, Averina O, Hildebrandt TB. Surprisingly long survival of premature conclusions about naked mole‐rat biology. Biol Rev Camb Philos Soc 2020; 96:376-393. [DOI: 10.1111/brv.12660] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/06/2020] [Accepted: 10/13/2020] [Indexed: 12/11/2022]
Affiliation(s)
- Stan Braude
- Biology Department Washington University, One Brookings Drive St. Louis MO 63130 U.S.A
| | - Susanne Holtze
- Department of Reproduction Management Leibniz‐Institute for Zoo and Wildlife Research Berlin 10315 Germany
| | - Sabine Begall
- Department of General Zoology, Faculty of Biology University of Duisburg‐Essen, Universitätsstr Essen 45147 Germany
| | - Julia Brenmoehl
- Institute for Genome Biology Leibniz‐Institute for Farm Animal Biology Dummerstorf 18196 Germany
| | - Hynek Burda
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences Czech University of Life Sciences Praha 16500 Czech Republic
| | - Philip Dammann
- Department of General Zoology, Faculty of Biology University of Duisburg‐Essen, Universitätsstr Essen 45147 Germany
- University Hospital Essen Hufelandstr Essen 45141 Germany
| | - Delphine Marmol
- Molecular Physiology Research Unit (URPhyM), NARILIS University of Namur Namur 5000 Belgium
| | - Ekaterina Gorshkova
- Engelhardt Institute of Molecular Biology Russian Academy of Sciences, Vavilova str. 32 Moscow 119991 Russia
- Faculty of Biology Lomonosov Moscow State University Moscow 119991 Russia
| | - Yoshiyuki Henning
- University Hospital Essen Hufelandstr Essen 45141 Germany
- Institute of Physiology Department of General Zoology University of Duisburg Essen Germany
| | - Andreas Hoeflich
- Division Signal Transduction Institute for Genome Biology, Leibniz‐Institute for Farm Animal Biology, FBN Dummerstorf, Wilhelm‐Stahl‐Allee 2 Dummerstorf 18196 Germany
| | - Annika Höhn
- Department of Molecular Toxicology German Institute of Human Nutrition (DIfE) Potsdam‐Rehbrücke Nuthetal 14558 Germany
- German Center for Diabetes Research (DZD) München‐Neuherberg 85764 Germany
| | - Tobias Jung
- Department of Molecular Toxicology German Institute of Human Nutrition (DIfE) Potsdam‐Rehbrücke Nuthetal 14558 Germany
| | - Dania Hamo
- Charité ‐ Universitätsmedizin Berlin Berlin Institute of Health Center for Regenerative Therapies (BCRT) Berlin 13353 Germany
- German Rheumatism Research Centre Berlin (DRFZ) Berlin 10117 Germany
| | - Arne Sahm
- Computational Biology Group Leibniz Institute on Aging – Fritz Lipmann Institute Jena 07745 Germany
| | - Yury Shebzukhov
- Engelhardt Institute of Molecular Biology Russian Academy of Sciences, Vavilova str. 32 Moscow 119991 Russia
- Charité ‐ Universitätsmedizin Berlin Berlin Institute of Health Center for Regenerative Therapies (BCRT) Berlin 13353 Germany
| | - Radim Šumbera
- Faculty of Science University of South Bohemia České Budějovice 37005 Czech Republic
| | - Satomi Miwa
- Biosciences Institute, Edwardson building, Campus for Ageing and Vitality Newcastle University Newcastle upon Tyne NE4 5PL U.K
| | - Mikhail Y. Vyssokikh
- Belozersky Institute of Physico‐Chemical Biology Lomonosov Moscow State University Moscow 119991 Russia
| | - Thomas Zglinicki
- Biosciences Institute, Edwardson building, Campus for Ageing and Vitality Newcastle University Newcastle upon Tyne NE4 5PL U.K
| | - Olga Averina
- Belozersky Institute of Physico‐Chemical Biology Lomonosov Moscow State University Moscow 119991 Russia
| | - Thomas B. Hildebrandt
- Department of Reproduction Management Leibniz‐Institute for Zoo and Wildlife Research Berlin 10315 Germany
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13
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ANESTHETIC EFFECT OF DEXMEDETOMIDINE-KETAMINEMIDAZOLAM COMBINATION ADMINISTERED INTRAMUSCULARLY TO ZOO-HOUSED NAKED MOLE-RATS ( HETEROCEPHALUS GLABER). J Zoo Wildl Med 2020; 51:59-66. [PMID: 32212547 DOI: 10.1638/2019-0121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2019] [Indexed: 11/21/2022] Open
Abstract
In this study, adult intact male and female (n = 10) naked mole-rats (Heterocephalus glaber) were anesthetized using a combination of dexmedetomidine (0.06 mg/kg intramuscularly [IM]), ketamine (20 mg/kg IM), and midazolam (1.0 mg/kg IM). Atipamezole (1.0 mg/kg IM) and flumazenil (0.1 mg/kg IM) were administered 40 min after induction. Induction and recovery times were monitored and recorded. Vital parameters, including heart rate, respiratory rate, and SpO2, and reflexes were monitored every 5 min during the anesthetic period. Anesthetic induction was smooth and rapid. All monitored reflexes were lost within a median time of 60 sec (interquartile range, 15 sec). Heart rate and respiratory rate were significantly decreased from baseline, whereas there was no difference in SpO2 over the anesthetic period. The mean time to recovery was 15 ± 7 min (mean ± SD). One animal was found dead 40 min after apparent recovery, which is suspected to be an anesthetic-related death. Based on these findings, dexmedetomidine-ketamine-midazolam anesthesia is an effective anesthetic protocol in naked mole rats that provides a consistent anesthetic plane but should be used with caution in animals with underlying conditions.
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Ambar N, Eshar D, Shrader TC, Beaufrère H. Anesthetic Effects of Intramuscular Alfaxalone-Ketamine in Naked Mole Rats ( Heterocephalus glaber). JOURNAL OF THE AMERICAN ASSOCIATION FOR LABORATORY ANIMAL SCIENCE 2020; 59:539-545. [PMID: 32680579 DOI: 10.30802/aalas-jaalas-19-000170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this study, adult intact male and female (n = 10) naked mole rats (Heterocephalus glaber) were anesthetized by using a combination of ketamine (20 mg/kg IM), and alfaxalone (4.0 mg/kg IM). Induction and recovery times were recorded. Vital parameters, including heart rate, respiratory rate, and reflexes, were monitored every 5 min during the anesthetic period. Anesthetic induction was smooth and rapid. Induction time was significantly longer in male rats (median, 325 s; range, 180 to 385 s) than in females (median, 145 s; range, 118 to 180 s). In addition, overall duration of loss of righting reflex was shorter in male mole rats (median, 50 min; range, 36 to 65 min) than females (median, 70 min; range, 60 to 85 min). Males largely had intact withdrawal reflexes, whereas females showed variable loss of both forelimb and hindlimb withdrawal reflexes. Neither recovery time (mean ± 1 SD, 16 ± 13 min) nor vital parameters differed between sexes. None of animals showed any anesthesia-related adverse responses. According to these findings, intramuscular AK is a safe and effective protocol that provides brief, light anesthesia in male naked mole rats and deeper anesthesia in females. We recommend adding analgesics when this AK protocol is used for pain-inducing or invasive procedures, and further studies evaluating higher doses and different combinations are indicated.
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Affiliation(s)
- Neta Ambar
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas;,
| | - David Eshar
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
| | | | - Hugues Beaufrère
- Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Canada
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15
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Eshar D, Huckins GL, Shrader TC, Beaufrère H. Comparison of intramuscular administration of alfaxalone-ketamine-dexmedetomidine and alfaxalone-butorphanol-midazolam in naked mole-rats ( Heterocephalus glaber). Am J Vet Res 2020; 80:1089-1098. [PMID: 31763939 DOI: 10.2460/ajvr.80.12.1089] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To compare anesthetic effects of alfaxalone-ketamine-dexmedetomidine (AKD) and alfaxalone-butorphanol-midazolam (ABM) in naked mole-rats (Heterocephalus glaber). ANIMALS 20 naked mole-rats. PROCEDURES Naked mole-rats received AKD (alfaxalone, 2 mg/kg; ketamine, 20 mg/kg; and dexmedetomidine, 0.02 mg/kg; n = 10) or ABM (alfaxalone, 2 mg/kg; butorphanol, 2 mg/kg; and midazolam, 1 mg/kg; 9) IM; 1 animal was removed from the study. Atipamezole (I mg/kg) and flumazenil (0.1 mg/kg) were administered 40 minutes after anesthetic induction (defined as loss of the righting reflex) with AKD and ABM, respectively. Heart rate, respiratory rate, oxygen saturation, and reflexes were recorded every 5 minutes. RESULTS The ABM group had significantly longer median times for induction and recovery than the AKD group. Administration of ABM resulted in significantly lower respiratory rates than administration of AKD from time of anesthetic induction to 10 minutes after induction. Respiratory rate significantly decreased in the AKD group from I0 minutes after induction through the end of the anesthetic period but did not change over time in the ABM group. Males had higher respiratory rates in both groups. Loss of the righting reflex was still evident 40 minutes after induction in both groups. In the AKD group, all tested reflexes were absent from I0 to 40 minutes after induction; the ABM group had variable reflexes that recovered within individual animals over time. CONCLUSIONS AND CLINICAL RELEVANCE Both AKD and ABM provided effective immobilization in naked mole-rats, but AKD appeared to provide more consistent and deeper anesthesia, compared with administration of ABM.
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16
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Braude S, Holtze S, Hildebrandt T, Koch R. Naked mole‐rats do not disperse or deliver pups in correlation with moon phase. Afr J Ecol 2020. [DOI: 10.1111/aje.12721] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stan Braude
- Biology Department Washington University St. Louis Missouri
| | - Susanne Holtze
- Leibniz‐Instut fur Zoo und Wildtierforschung Berlin Germany
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17
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Schulze-Makuch D. The Naked Mole-Rat: An Unusual Organism with an Unexpected Latent Potential for Increased Intelligence? Life (Basel) 2019; 9:life9030076. [PMID: 31527499 PMCID: PMC6789728 DOI: 10.3390/life9030076] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/13/2019] [Accepted: 08/28/2019] [Indexed: 11/24/2022] Open
Abstract
Naked mole-rats are eusocial, hairless mammals that are uniquely adapted to their harsh, low-oxygen subsurface habitat. Although their encephalization quotient, a controversial marker of intelligence, is low, they exhibit many features considered tell-tale signs of highly intelligent species on our planet including longevity, plasticity, social cohesion and interaction, rudimentary language, sustainable farming abilities, and maintaining sanitary conditions in their self-built complex housing structures. It is difficult to envision how naked mole-rats would reach even higher levels of intelligence in their natural sensory-challenged habitat, but such an evolutionary path cannot be excluded if they would expand their range onto the earth’s surface.
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Affiliation(s)
- Dirk Schulze-Makuch
- Astrobiology Group, Center for Astronomy and Astrophysics (ZAA), Technical University Berlin, 10623 Berlin, Germany.
- School of the Environment, Washington State University, Pullman, WA 99163, USA.
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18
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Langer BE, Hiller M. TFforge utilizes large-scale binding site divergence to identify transcriptional regulators involved in phenotypic differences. Nucleic Acids Res 2019; 47:e19. [PMID: 30496469 PMCID: PMC6393245 DOI: 10.1093/nar/gky1200] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 11/06/2018] [Accepted: 11/15/2018] [Indexed: 12/19/2022] Open
Abstract
Changes in gene regulation are important for phenotypic and in particular morphological evolution. However, it remains challenging to identify the transcription factors (TFs) that contribute to differences in gene regulation and thus to phenotypic differences between species. Here, we present TFforge (Transcription Factor forward genomics), a computational method to identify TFs that are involved in the loss of phenotypic traits. TFforge screens an input set of regulatory genomic regions to detect TFs that exhibit a significant binding site divergence signature in species that lost a particular phenotypic trait. Using simulated data of modular and pleiotropic regulatory elements, we show that TFforge can identify the correct TFs for many different evolutionary scenarios. We applied TFforge to available eye regulatory elements to screen for TFs that exhibit a significant binding site decay signature in subterranean mammals. This screen identified interacting and co-binding eye-related TFs, and thus provides new insights into which TFs likely contribute to eye degeneration in these species. TFforge has broad applicability to identify the TFs that contribute to phenotypic changes between species, and thus can help to unravel the gene-regulatory differences that underlie phenotypic evolution.
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Affiliation(s)
- Björn E Langer
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology Dresden, Germany
| | - Michael Hiller
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology Dresden, Germany
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19
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Langer BE, Roscito JG, Hiller M. REforge Associates Transcription Factor Binding Site Divergence in Regulatory Elements with Phenotypic Differences between Species. Mol Biol Evol 2019; 35:3027-3040. [PMID: 30256993 PMCID: PMC6278867 DOI: 10.1093/molbev/msy187] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Elucidating the genomic determinants of morphological differences between species is key to understanding how morphological diversity evolved. While differences in cis-regulatory elements are an important genetic source for morphological evolution, it remains challenging to identify regulatory elements involved in phenotypic differences. Here, we present Regulatory Element forward genomics (REforge), a computational approach that detects associations between transcription factor binding site divergence in putative regulatory elements and phenotypic differences between species. By simulating regulatory element evolution in silico, we show that this approach has substantial power to detect such associations. To validate REforge on real data, we used known binding motifs for eye-related transcription factors and identified significant binding site divergence in vision-impaired subterranean mammals in 1% of all conserved noncoding elements. We show that these genomic regions are significantly enriched in regulatory elements that are specifically active in mouse eye tissues, and that several of them are located near genes, which are required for eye development and photoreceptor function and are implicated in human eye disorders. Thus, our genome-wide screen detects widespread divergence of eye-regulatory elements and highlights regulatory regions that likely contributed to eye degeneration in subterranean mammals. REforge has broad applicability to detect regulatory elements that could be involved in many other phenotypes, which will help to reveal the genomic basis of morphological diversity.
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Affiliation(s)
- Björn E Langer
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Juliana G Roscito
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Michael Hiller
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
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20
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Cain BW, Reynolds T, Sarko DK. Superficial, suprahyoid, and infrahyoid neck musculature in naked mole-rats (Heterocephalus glaber): Relative size and potential contributions to independent movement of the lower incisors. J Morphol 2019; 280:1185-1196. [PMID: 31180596 DOI: 10.1002/jmor.21022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/22/2019] [Accepted: 05/24/2019] [Indexed: 11/06/2022]
Abstract
Naked mole-rats (Heterocephalus glaber) are fossorial, eusocial rodents that exhibit the unusual capability of moving their lower incisors independently in lateral and rostroventral directions. The evolution of this trait would presumably also involve concurrent alterations in neck musculature to support and control movements of the lower incisors. In order to assess morphological adaptations that might facilitate these movements, we performed detailed dissections of the neck musculature of adult naked mole-rats. In addition to characterizing attachment sites of superficial, suprahyoid, and infrahyoid musculature, we also quantified muscle mass and mandibular features thought to be associated with gape (condyle height, condyle length, and jaw length). Based on muscle attachment sites, the platysma myoides may contribute to lateral movement of the lower incisor and hemi-mandible in naked mole-rats. The large digastric muscle is likely to be a main contributor to rostroventral movement of each lower incisor. The geniohyoid and mylohyoid muscles also likely contribute to rostroventral movements of the lower incisors, and the mylohyoid may also produce lateral spreading of the hemi-mandibles. The transverse mandibular (intermandibularis) muscle likely serves to reposition the lower incisors back to a midline orientation following a movement.
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Affiliation(s)
- Blake W Cain
- Southern Illinois University School of Medicine, Department of Anatomy, Carbondale, Illinois
| | - Taylor Reynolds
- Southern Illinois University School of Medicine, Department of Anatomy, Carbondale, Illinois
| | - Diana K Sarko
- Southern Illinois University School of Medicine, Department of Anatomy, Carbondale, Illinois
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21
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Barone CM, Douma S, Reijntjes DOJ, Browe BM, Köppl C, Klump G, Park TJ, Pyott SJ. Altered cochlear innervation in developing and mature naked and Damaraland mole rats. J Comp Neurol 2019; 527:2302-2316. [PMID: 30861124 PMCID: PMC6767702 DOI: 10.1002/cne.24682] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 03/06/2019] [Accepted: 03/07/2019] [Indexed: 01/04/2023]
Abstract
Compared to many other rodent species, naked mole rats (Heterocephalus glaber) have elevated auditory thresholds, poor frequency selectivity, and limited ability to localize sound. Because the cochlea is responsible for encoding and relaying auditory signals to the brain, we used immunofluorescence and quantitative image analysis to examine cochlear innervation in mature and developing naked mole rats compared to mice (Mus musculus), gerbils (Meriones unguiculatus), and Damaraland mole rats (Fukomys damarensis), another subterranean rodent. In comparison to mice and gerbils, we observed alterations in afferent and efferent innervation as well as their patterns of developmental refinement in naked and Damaraland mole rats. These alterations were, however, not always shared similarly between naked and Damaraland mole rats. Most conspicuously, in both naked and Damaraland mole rats, inner hair cell (IHC) afferent ribbon density was reduced, whereas outer hair cell afferent ribbon density was increased. Naked and Damaraland mole rats also showed reduced lateral and medial efferent terminal density. Developmentally, naked mole rats showed reduced and prolonged postnatal reorganization of afferent and efferent innervation. Damaraland mole rats showed no evidence of postnatal reorganization. Differences in cochlear innervation specifically between the two subterranean rodents and more broadly among rodents provides insight into the cochlear mechanisms that enhance frequency sensitivity and sound localization, maturation of the auditory system, and the evolutionary adaptations occurring in response to subterranean environments.
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Affiliation(s)
- Catherine M Barone
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - Sytse Douma
- Department of Otorhinolaryngology and Head/Neck Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Daniël O J Reijntjes
- Department of Otorhinolaryngology and Head/Neck Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Brigitte M Browe
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - Christine Köppl
- Cluster of Excellence "Hearing4All", Department of Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Georg Klump
- Cluster of Excellence "Hearing4All", Department of Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Thomas J Park
- Laboratory of Integrative Neuroscience, Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - Sonja J Pyott
- Department of Otorhinolaryngology and Head/Neck Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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22
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Emerling CA. Regressed but Not Gone: Patterns of Vision Gene Loss and Retention in Subterranean Mammals. Integr Comp Biol 2019; 58:441-451. [PMID: 29697812 DOI: 10.1093/icb/icy004] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Regressive evolution involves the degradation of formerly useful traits as organisms invade novel ecological niches. In animals, committing to a strict subterranean habit can lead to regression of the eyes, likely due to a limited exposure to light. Several lineages of subterranean mammals show evidence of such degeneration, which can include decreased organization of the retina, malformation of the lens, and subcutaneous positioning of the eye. Advances in DNA sequencing have revealed that this regression co-occurs with a degradation of genomic loci encoding visual functions, including protein-coding genes. Other dim light-adapted vertebrates with normal ocular anatomy, such as nocturnal and aquatic species, also demonstrate evidence of visual gene loss, but the absence of comparative studies has led to the untested assumption that subterranean mammals are special in the degree of this genomic regression. Additionally, previous studies have shown that not all vision genes have been lost in subterranean mammals, but it is unclear whether they are under relaxed selection and will ultimately be lost, are maintained due to pleiotropy or if natural selection is favoring the retention of the eye and certain critical underlying loci. Here I report that vision gene loss in subterranean mammals tends to be more extensive in quantity and differs in distribution from other dim light-adapted mammals, although some committed subterranean mammals demonstrate significant overlap with nocturnal microphthalmic species. In addition, blind subterranean mammals retain functional orthologs of non-pleiotropic visual genes that are evolving at rates consistent with purifying selection. Together, these results suggest that although living underground tends to lead to major losses of visual functions, natural selection is maintaining genes that support the eye, perhaps as an organ for circadian and/or circannual entrainment.
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Affiliation(s)
- Christopher A Emerling
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA 94720, USA
- Institut des Sciences de l'Evolution de Montpellier (ISEM), Université de Montpellier, CNRS, IRD, EPHE, 34090 Montpellier, France
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23
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Dennis JC, Stilwell NK, Smith TD, Park TJ, Bhatnagar KP, Morrison EE. Is the Mole Rat Vomeronasal Organ Functional? Anat Rec (Hoboken) 2019; 303:318-329. [DOI: 10.1002/ar.24060] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 11/02/2018] [Accepted: 12/13/2018] [Indexed: 11/06/2022]
Affiliation(s)
- John C. Dennis
- Department of Anatomy, Physiology, and Pharmacology Auburn University Auburn Alabama
| | | | - Timothy D. Smith
- School of Physical Therapy Slippery Rock University Slippery Rock Pennsylvania
- Department of Anthropology University of Pittsburgh Pittsburgh Pennsylvania
| | - Thomas J. Park
- Department of Biological Sciences University of Illinois at Chicago Chicago Illinois
| | - Kunwar P. Bhatnagar
- Department of Anatomical Sciences and Neurobiology University of Louisville School of Medicine Louisville Kentucky
| | - Edward E. Morrison
- Department of Anatomy, Physiology, and Pharmacology Auburn University Auburn Alabama
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24
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Browe BM, Vice EN, Park TJ. Naked Mole‐Rats: Blind, Naked, and Feeling No Pain. Anat Rec (Hoboken) 2018; 303:77-88. [PMID: 30365235 DOI: 10.1002/ar.23996] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 01/15/2018] [Accepted: 01/24/2018] [Indexed: 01/05/2023]
Affiliation(s)
- Brigitte M. Browe
- Department of Biological Sciences University of Illinois at Chicago, Laboratory of Integrative Neuroscience 840 West Taylor St, Chicago Illinois
| | - Emily N. Vice
- Department of Biological Sciences University of Illinois at Chicago, Laboratory of Integrative Neuroscience 840 West Taylor St, Chicago Illinois
| | - Thomas J. Park
- Department of Biological Sciences University of Illinois at Chicago, Laboratory of Integrative Neuroscience 840 West Taylor St, Chicago Illinois
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Roscito JG, Sameith K, Parra G, Langer BE, Petzold A, Moebius C, Bickle M, Rodrigues MT, Hiller M. Phenotype loss is associated with widespread divergence of the gene regulatory landscape in evolution. Nat Commun 2018; 9:4737. [PMID: 30413698 PMCID: PMC6226452 DOI: 10.1038/s41467-018-07122-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 10/15/2018] [Indexed: 02/07/2023] Open
Abstract
Detecting the genomic changes underlying phenotypic changes between species is a main goal of evolutionary biology and genomics. Evolutionary theory predicts that changes in cis-regulatory elements are important for morphological changes. We combined genome sequencing, functional genomics and genome-wide comparative analyses to investigate regulatory elements in lineages that lost morphological traits. We first show that limb loss in snakes is associated with widespread divergence of limb regulatory elements. We next show that eye degeneration in subterranean mammals is associated with widespread divergence of eye regulatory elements. In both cases, sequence divergence results in an extensive loss of transcription factor binding sites. Importantly, diverged regulatory elements are associated with genes required for normal limb patterning or normal eye development and function, suggesting that regulatory divergence contributed to the loss of these phenotypes. Together, our results show that genome-wide decay of the phenotype-specific cis-regulatory landscape is a hallmark of lost morphological traits. Cis-regulatory elements are important factors for morphological changes. Here, the authors show widespread divergence of limb and eye regulatory elements in limb loss in snakes and eye degeneration in subterranean mammals respectively.
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Affiliation(s)
- Juliana G Roscito
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany.,Center for Systems Biology Dresden, Dresden, 01307, Germany.,Instituto de Biociências, Universidade de São Paulo, São Paulo, 05508-090, Brazil
| | - Katrin Sameith
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany.,Center for Systems Biology Dresden, Dresden, 01307, Germany
| | - Genis Parra
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany.,Center for Systems Biology Dresden, Dresden, 01307, Germany
| | - Bjoern E Langer
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany.,Center for Systems Biology Dresden, Dresden, 01307, Germany
| | - Andreas Petzold
- Center for Regenerative Therapies TU Dresden, Dresden, 01307, Germany
| | - Claudia Moebius
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany
| | - Marc Bickle
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany
| | | | - Michael Hiller
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, 01307, Germany. .,Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany. .,Center for Systems Biology Dresden, Dresden, 01307, Germany.
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26
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Sun H, Zhang Y, Shi Y, Li Y, Li W, Wang Z. Evolution of the CLOCK and BMAL1 genes in a subterranean rodent species (Lasiopodomys mandarinus). Int J Biol Macromol 2018; 109:932-940. [DOI: 10.1016/j.ijbiomac.2017.11.076] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 11/10/2017] [Accepted: 11/12/2017] [Indexed: 12/01/2022]
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27
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Partha R, Chauhan BK, Ferreira Z, Robinson JD, Lathrop K, Nischal KK, Chikina M, Clark NL. Subterranean mammals show convergent regression in ocular genes and enhancers, along with adaptation to tunneling. eLife 2017; 6:e25884. [PMID: 29035697 PMCID: PMC5643096 DOI: 10.7554/elife.25884] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 08/22/2017] [Indexed: 12/22/2022] Open
Abstract
The underground environment imposes unique demands on life that have led subterranean species to evolve specialized traits, many of which evolved convergently. We studied convergence in evolutionary rate in subterranean mammals in order to associate phenotypic evolution with specific genetic regions. We identified a strong excess of vision- and skin-related genes that changed at accelerated rates in the subterranean environment due to relaxed constraint and adaptive evolution. We also demonstrate that ocular-specific transcriptional enhancers were convergently accelerated, whereas enhancers active outside the eye were not. Furthermore, several uncharacterized genes and regulatory sequences demonstrated convergence and thus constitute novel candidate sequences for congenital ocular disorders. The strong evidence of convergence in these species indicates that evolution in this environment is recurrent and predictable and can be used to gain insights into phenotype-genotype relationships.
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Affiliation(s)
- Raghavendran Partha
- Department of Computational and Systems BiologyUniversity of PittsburghPittsburghUnited States
| | - Bharesh K Chauhan
- UPMC Eye CenterChildren’s Hospital of PittsburghPittsburghUnited States
- Department of OphthalmologyUniversity of Pittsburgh School of MedicinePittsburghUnited States
| | - Zelia Ferreira
- Department of Computational and Systems BiologyUniversity of PittsburghPittsburghUnited States
| | - Joseph D Robinson
- Department of Molecular and Cell BiologyUniversity of CaliforniaBerkeleyUnited States
| | - Kira Lathrop
- UPMC Eye CenterChildren’s Hospital of PittsburghPittsburghUnited States
- Department of OphthalmologyUniversity of Pittsburgh School of MedicinePittsburghUnited States
| | - Ken K Nischal
- UPMC Eye CenterChildren’s Hospital of PittsburghPittsburghUnited States
- Department of OphthalmologyUniversity of Pittsburgh School of MedicinePittsburghUnited States
| | - Maria Chikina
- Department of Computational and Systems BiologyUniversity of PittsburghPittsburghUnited States
| | - Nathan L Clark
- Department of Computational and Systems BiologyUniversity of PittsburghPittsburghUnited States
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28
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Ear Structures of the Naked Mole-Rat, Heterocephalus glaber, and Its Relatives (Rodentia: Bathyergidae). PLoS One 2016; 11:e0167079. [PMID: 27926945 PMCID: PMC5142786 DOI: 10.1371/journal.pone.0167079] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 11/08/2016] [Indexed: 11/21/2022] Open
Abstract
Although increasingly popular as a laboratory species, very little is known about the peripheral auditory system of the naked mole-rat, Heterocephalus glaber. In this study, middle and inner ears of naked mole-rats of a range of ages were examined using micro-computed tomography and dissection. The ears of five other bathyergid species (Bathyergus suillus, Cryptomys hottentotus, Fukomys micklemi, Georychus capensis and Heliophobius argenteocinereus) were examined for comparative purposes. The middle ears of bathyergids show features commonly found in other members of the Ctenohystrica rodent clade, including a fused malleus and incus, a synovial stapedio-vestibular articulation and the loss of the stapedius muscle. Heterocephalus deviates morphologically from the other bathyergids examined in that it has a more complex mastoid cavity structure, poorly-ossified processes of the malleus and incus, a ‘columelliform’ stapes and fewer cochlear turns. Bathyergids have semicircular canals with unusually wide diameters relative to their radii of curvature. How the lateral semicircular canal reaches the vestibule differs between species. Heterocephalus has much more limited high-frequency hearing than would be predicted from its small ear structures. The spongy bone forming its ossicular processes, the weak incudo-stapedial articulation, the columelliform stapes and (compared to other bathyergids) reduced cochlear coiling are all potentially degenerate features which might reflect a lack of selective pressure on its peripheral auditory system. Substantial intraspecific differences were found in certain middle and inner ear structures, which might also result from relaxed selective pressures. However, such interpretations must be treated with caution in the absence of experimental evidence.
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29
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Kott O, Němec P, Fremlová A, Mazoch V, Šumbera R. Behavioural Tests Reveal Severe Visual Deficits in the Strictly Subterranean African Mole-Rats (Bathyergidae) but Efficient Vision in the Fossorial Rodent Coruro (Spalacopus cyanus, Octodontidae). Ethology 2016. [DOI: 10.1111/eth.12515] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ondřej Kott
- Department of Zoology; Faculty of Science; University of South Bohemia; České Budějovice Czech Republic
| | - Pavel Němec
- Department of Zoology; Faculty of Science; Charles University in Prague; Prague Czech Republic
| | - Aneta Fremlová
- Department of Zoology; Faculty of Science; University of South Bohemia; České Budějovice Czech Republic
| | - Vladimír Mazoch
- Department of Zoology; Faculty of Science; University of South Bohemia; České Budějovice Czech Republic
| | - Radim Šumbera
- Department of Zoology; Faculty of Science; University of South Bohemia; České Budějovice Czech Republic
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30
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Toor I, Clement D, Carlson EN, Holmes MM. Olfaction and social cognition in eusocial naked mole-rats, Heterocephalus glaber. Anim Behav 2015. [DOI: 10.1016/j.anbehav.2015.06.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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31
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Corfield JR, Parsons S, Harimoto Y, Acosta ML. Retinal anatomy of the New Zealand kiwi: structural traits consistent with their nocturnal behavior. Anat Rec (Hoboken) 2014; 298:771-9. [PMID: 25346176 DOI: 10.1002/ar.23080] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 09/10/2014] [Accepted: 09/20/2014] [Indexed: 11/09/2022]
Abstract
Kiwi (Apteryx spp.) have a visual system unlike that of other nocturnal birds, and have specializations to their auditory, olfactory, and tactile systems. Eye size, binocular visual fields and visual brain centers in kiwi are proportionally the smallest yet recorded among birds. Given the many unique features of the kiwi visual system, we examined the laminar organization of the kiwi retina to determine if they evolved increased light sensitivity with a shift to a nocturnal niche or if they retained features of their diurnal ancestor. The laminar organization of the kiwi retina was consistent with an ability to detect low light levels similar to that of other nocturnal species. In particular, the retina appeared to have a high proportion of rod photoreceptors as compared to diurnal species, as evidenced by a thick outer nuclear layer, and also numerous thin photoreceptor segments intercalated among the conical shaped cone photoreceptor inner segments. Therefore, the retinal structure of kiwi was consistent with increased light sensitivity, although other features of the visual system, such as eye size, suggest a reduced reliance on vision. The unique combination of a nocturnal retina and smaller than expected eye size, binocular visual fields, and brain regions make the kiwi visual system unlike that of any bird examined to date. Whether these features of their visual system are an evolutionary design that meets their specific visual needs or are a remnant of a kiwi ancestor that relied more heavily on vision is yet to be determined.
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Affiliation(s)
- Jeremy R Corfield
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
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Leitch DB, Sarko DK, Catania KC. Brain mass and cranial nerve size in shrews and moles. Sci Rep 2014; 4:6241. [PMID: 25174995 PMCID: PMC4150104 DOI: 10.1038/srep06241] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 07/23/2014] [Indexed: 11/09/2022] Open
Abstract
We investigated the relationship between body size, brain size, and fibers in selected cranial nerves in shrews and moles. Species include tiny masked shrews (S. cinereus) weighing only a few grams and much larger mole species weighing up to 90 grams. It also includes closely related species with very different sensory specializations - such as the star-nosed mole and the common, eastern mole. We found that moles and shrews have tiny optic nerves with fiber counts not correlated with body or brain size. Auditory nerves were similarly small but increased in fiber number with increasing brain and body size. Trigeminal nerve number was by far the largest and also increased with increasing brain and body size. The star-nosed mole was an outlier, with more than twice the number of trigeminal nerve fibers than any other species. Despite this hypertrophied cranial nerve, star-nosed mole brains were not larger than predicted from body size, suggesting that magnification of their somatosensory systems does not result in greater overall CNS size.
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Affiliation(s)
- Duncan B. Leitch
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Diana K. Sarko
- Department of Anatomy, Cell Biology & Physiology, Edward Via College of Osteopathic Medicine, Spartanburg, SC, USA
| | - Kenneth C. Catania
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
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33
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Kott O, Moritz RE, Šumbera R, Burda H, Němec P. Light propagation in burrows of subterranean rodents: tunnel system architecture but not photoreceptor sensitivity limits light sensation range. J Zool (1987) 2014. [DOI: 10.1111/jzo.12152] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- O. Kott
- Department of Zoology; Faculty of Science; University of South Bohemia; České Budějovice Czech Republic
| | - R. E. Moritz
- Department of General Zoology; Faculty of Biology; University of Duisburg-Essen; Essen Germany
| | - R. Šumbera
- Department of Zoology; Faculty of Science; University of South Bohemia; České Budějovice Czech Republic
| | - H. Burda
- Department of General Zoology; Faculty of Biology; University of Duisburg-Essen; Essen Germany
| | - P. Němec
- Department of Zoology; Faculty of Science; Charles University in Prague; Prague Czech Republic
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34
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Amrein I, Becker AS, Engler S, Huang SH, Müller J, Slomianka L, Oosthuizen MK. Adult neurogenesis and its anatomical context in the hippocampus of three mole-rat species. Front Neuroanat 2014; 8:39. [PMID: 24904308 PMCID: PMC4033039 DOI: 10.3389/fnana.2014.00039] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 04/30/2014] [Indexed: 12/03/2022] Open
Abstract
African mole-rats (family Bathyergidae) are small to medium sized, long-lived, and strictly subterranean rodents that became valuable animal models as a result of their longevity and diversity in social organization. The formation and integration of new hippocampal neurons in adult mammals (adult hippocampal neurogenesis, AHN) correlates negatively with age and positively with habitat complexity. Here we present quantitative data on AHN in wild-derived mole-rats of 1 year and older, and briefly describe its anatomical context including markers of neuronal function (calbindin and parvalbumin). Solitary Cape mole-rats (Georychus capensis), social highveld mole-rats (Cryptomys hottentotus pretoriae), and eusocial naked mole-rats (Heterocephalus glaber) were assessed. Compared to other rodents, the hippocampal formation in mole-rats is small, but shows a distinct cytoarchitecture in the dentate gyrus and CA1. Distributions of the calcium-binding proteins differ from those seen in rodents; e.g., calbindin in CA3 of naked mole-rats distributes similar to the pattern seen in early primate development, and calbindin staining extends into the stratum lacunosum-moleculare of Cape mole-rats. Proliferating cells and young neurons are found in low numbers in the hippocampus of all three mole-rat species. Resident granule cell numbers are low as well. Proliferating cells expressed as a percentage of resident granule cells are in the range of other rodents, while the percentage of young neurons is lower than that observed in surface dwelling rodents. Between mole-rat species, we observed no difference in the percentage of proliferating cells. The percentages of young neurons are high in social highveld and naked mole-rats, and low in solitary Cape mole-rats. The findings support that proliferation is regulated independently of average life expectancy and habitat. Instead, neuronal differentiation reflects species-specific demands, which appear lower in subterranean rodents.
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Affiliation(s)
- Irmgard Amrein
- Division of Functional Neuroanatomy, Institute of Anatomy, University of ZürichZürich, Switzerland
| | - Anton S. Becker
- Division of Functional Neuroanatomy, Institute of Anatomy, University of ZürichZürich, Switzerland
| | - Stefanie Engler
- Division of Functional Neuroanatomy, Institute of Anatomy, University of ZürichZürich, Switzerland
| | - Shih-hui Huang
- Division of Functional Neuroanatomy, Institute of Anatomy, University of ZürichZürich, Switzerland
| | - Julian Müller
- Division of Functional Neuroanatomy, Institute of Anatomy, University of ZürichZürich, Switzerland
| | - Lutz Slomianka
- Division of Functional Neuroanatomy, Institute of Anatomy, University of ZürichZürich, Switzerland
| | - Maria K. Oosthuizen
- Department of Zoology and Entomology, University of PretoriaPretoria, South Africa
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35
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Kemp AD, Christopher Kirk E. Eye size and visual acuity influence vestibular anatomy in mammals. Anat Rec (Hoboken) 2014; 297:781-90. [PMID: 24591307 DOI: 10.1002/ar.22892] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 12/23/2013] [Indexed: 11/12/2022]
Abstract
The semicircular canals of the inner ear detect head rotations and trigger compensatory movements that stabilize gaze and help maintain visual fixation. Mammals with large eyes and high visual acuity require precise gaze stabilization mechanisms because they experience diminished visual functionality at low thresholds of uncompensated motion. Because semicircular canal radius of curvature is a primary determinant of canal sensitivity, species with large canal radii are expected to be capable of more precise gaze stabilization than species with small canal radii. Here, we examine the relationship between mean semicircular canal radius of curvature, eye size, and visual acuity in a large sample of mammals. Our results demonstrate that eye size and visual acuity both explain a significant proportion of the variance in mean canal radius of curvature after statistically controlling for the effects of body mass and phylogeny. These findings suggest that variation in mean semicircular canal radius of curvature among mammals is partly the result of selection for improved gaze stabilization in species with large eyes and acute vision. Our results also provide a possible functional explanation for the small semicircular canal radii of fossorial mammals and plesiadapiforms.
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Affiliation(s)
- Addison D Kemp
- Department of Anthropology, University of Texas at Austin, Texas
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36
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Seki F, Hikishima K, Nambu S, Okanoya K, Okano HJ, Sasaki E, Miura K, Okano H. Multidimensional MRI-CT atlas of the naked mole-rat brain (Heterocephalus glaber). Front Neuroanat 2013; 7:45. [PMID: 24391551 PMCID: PMC3868886 DOI: 10.3389/fnana.2013.00045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 11/27/2013] [Indexed: 11/13/2022] Open
Abstract
Naked mole-rats have a variety of distinctive features such as the organization of a hierarchical society (known as eusociality), extraordinary longevity, and cancer resistance; thus, it would be worthwhile investigating these animals in detail. One important task is the preparation of a brain atlas database that provide comprehensive information containing multidimensional data with various image contrasts, which can be achievable using a magnetic resonance imaging (MRI). Advanced MRI techniques such as diffusion tensor imaging (DTI), which generates high contrast images of fiber structures, can characterize unique morphological properties in addition to conventional MRI. To obtain high spatial resolution images, MR histology, DTI, and X-ray computed tomography were performed on the fixed adult brain. Skull and brain structures were segmented as well as reconstructed in stereotaxic coordinates. Data were also acquired for the neonatal brain to allow developmental changes to be observed. Moreover, in vivo imaging of naked mole-rats was established as an evaluation tool of live animals. The data obtained comprised three-dimensional (3D) images with high tissue contrast as well as stereotaxic coordinates. Developmental differences in the visual system were highlighted in particular by DTI. Although it was difficult to delineate optic nerves in the mature adult brain, parts of them could be distinguished in the immature neonatal brain. From observation of cortical thickness, possibility of high somatosensory system development replaced to the visual system was indicated. 3D visualization of brain structures in the atlas as well as the establishment of in vivo imaging would promote neuroimaging researches towards detection of novel characteristics of eusocial naked mole-rats.
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Affiliation(s)
- Fumiko Seki
- Department of Physiology, Keio University School of Medicine Tokyo, Japan ; Central Institute for Experimental Animals Kanagawa, Japan
| | - Keigo Hikishima
- Department of Physiology, Keio University School of Medicine Tokyo, Japan ; Central Institute for Experimental Animals Kanagawa, Japan
| | - Sanae Nambu
- Laboratory for Symbolic Cognitive Development, RIKEN Brain Science Institute Saitama, Japan
| | - Kazuo Okanoya
- Japan Science and Technology Exploratory Research for Advanced Technology Okanoya Emotional Information Project Saitama, Japan ; Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo Tokyo, Japan
| | - Hirotaka J Okano
- Division of Regenerative Medicine, Jikei University School of Medicine, Tokyo, Japan
| | - Erika Sasaki
- Department of Physiology, Keio University School of Medicine Tokyo, Japan ; Central Institute for Experimental Animals Kanagawa, Japan
| | - Kyoko Miura
- Department of Physiology, Keio University School of Medicine Tokyo, Japan ; Precursory Research for Embryonic Science and Technology, Japan Science and Technology Saitama, Japan
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine Tokyo, Japan ; Riken Keio University Joint Research Laboratory, RIKEN Brain Science Institute Saitama, Japan
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37
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Deacon RMJ, Dulu TD, Patel NB. Naked mole-rats: behavioural phenotyping and comparison with C57BL/6 mice. Behav Brain Res 2012; 231:193-200. [PMID: 22440234 DOI: 10.1016/j.bbr.2012.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 03/01/2012] [Accepted: 03/05/2012] [Indexed: 02/03/2023]
Abstract
Naked mole-rats (NMR) live underground in large eusocial colonies in East Africa. They are extremely long-lived, some individuals having a lifespan of over 30 years. This has attracted research into longevity and possibly neurodegenerative disorders. However, very little is known about their basic behaviour, particularly in tests commonly used to characterise the behaviour of the laboratory rat and mouse, for which there is an enormous database. Recently the authors carried out comprehensive behavioural phenotyping on NMRs, comparing them on most tasks directly with C57BL/6 mice, the strain for which there is the largest behavioural database. The NMR colony had been obtained from the wild originally, but housed in an animal facility for about two years. Large inter-species differences in behaviour were seen between the mice and the NMRs. The latter had generally poor sensorimotor function, including cutaneous sensation, strength and even grasp reflexes. They were often reluctant to enter or head-dip into small holes that mice readily entered. Their vision (generally considered to be very poor) was sufficient to distinguish the two zones of a light-dark box. Although, as expected, the NMRs were capable of burrowing and digging, when individually housed they did not shred cotton material to make nests. Shredding was seen in a colony cage containing a queen, but no nests were made there even when a nesting box was provided. In cognitive testing, although, unlike mice and rats, they did not spontaneously alternate in a T-maze, they learnt rewarded alternation and a cued position task well. This study demonstrates how behaviour uniquely reflects the natural environment in which these unusual animals have evolved and live, and provides baseline data for future work.
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Affiliation(s)
- R M J Deacon
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
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38
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Abstract
Naked mole rats are mouse-sized rodents that have become an important animal model in biomedical research. They play a unique mammalian role in behavioral and ecophysiological research of life underground. This chapter studies the general physiology, anatomy of organ systems, husbandry, and uses in research of the naked mole rats. Naked mole rats belong to the order Rodentia in that they have two incisor teeth on the upper and lower arcade that continuously grow. The skin is loose, wrinkled, and brownish pink in color. The body is for the most part absent of hairs with the exception of tactile hairs that are regularly arranged throughout the body and which are particularly prominent around the face and to a lesser extent on the tail. They are typically housed at 28–30°C, and at 50–60% relative humidity. Because naked mole rats are social and have cooperative behaviors, the study of their conduct has more applicability to people. The chapter describes the models of experimental research on the naked mole rat such as the model of reproductive suppression, model of somatosensory processing, model of bone elongation, and model of aging.
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Brecht M, Naumann R, Anjum F, Wolfe J, Munz M, Mende C, Roth-Alpermann C. The neurobiology of Etruscan shrew active touch. Philos Trans R Soc Lond B Biol Sci 2011; 366:3026-36. [PMID: 21969684 PMCID: PMC3172601 DOI: 10.1098/rstb.2011.0160] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The Etruscan shrew, Suncus etruscus, is not only the smallest terrestrial mammal, but also one of the fastest and most tactile hunters described to date. The shrew's skeletal muscle consists entirely of fast-twitch types and lacks slow fibres. Etruscan shrews detect, overwhelm, and kill insect prey in large numbers in darkness. The cricket prey is exquisitely mechanosensitive and fast-moving, and is as big as the shrew itself. Experiments with prey replica show that shape cues are both necessary and sufficient for evoking attacks. Shrew attacks are whisker guided by motion- and size-invariant Gestalt-like prey representations. Shrews often attack their prey prior to any signs of evasive manoeuvres. Shrews whisk at frequencies of approximately 14 Hz and can react with latencies as short as 25-30 ms to prey movement. The speed of attacks suggests that shrews identify and classify prey with a single touch. Large parts of the shrew's brain respond to vibrissal touch, which is represented in at least four cortical areas comprising collectively about a third of the cortical volume. Etruscan shrews can enter a torpid state and reduce their body temperature; we observed that cortical response latencies become two to three times longer when body temperature drops from 36°C to 24°C, suggesting that endothermy contributes to the animal's high-speed sensorimotor performance. We argue that small size, high-speed behaviour and extreme dependence on touch are not coincidental, but reflect an evolutionary strategy, in which the metabolic costs of small body size are outweighed by the advantages of being a short-range high-speed touch and kill predator.
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Affiliation(s)
- Michael Brecht
- BCCN, Humboldt University Berlin, Philippstrasse 13, House 6, 10115 Berlin, Germany.
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40
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Endocrine function and neurobiology of the longest-living rodent, the naked mole-rat. Exp Gerontol 2011; 46:116-23. [DOI: 10.1016/j.exger.2010.09.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 09/02/2010] [Accepted: 09/09/2010] [Indexed: 02/04/2023]
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41
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Schleich CE, Vielma A, Glösmann M, Palacios AG, Peichl L. Retinal photoreceptors of two subterranean tuco-tuco species (Rodentia, Ctenomys): morphology, topography, and spectral sensitivity. J Comp Neurol 2010; 518:4001-15. [PMID: 20737597 DOI: 10.1002/cne.22440] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Traditionally, vision was thought to be useless for animals living in dark underground habitats, but recent studies in a range of subterranean rodent species have shown a large diversity of eye features, from small subcutaneous eyes to normal-sized functional eyes. We analyzed the retinal photoreceptors in the subterranean hystricomorph rodents Ctenomys talarum and Ctenomys magellanicus to elucidate whether adaptation was to their near-lightless burrows or rather to their occasional diurnal surface activity. Both species had normally developed eyes. Overall photoreceptor densities were comparatively low (95,000-150,000/mm(2) in C. magellanicus, 110,000-200,000/mm(2) in C. talarum), and cone proportions were rather high (10-31% and 14-31%, respectively). The majority of cones expressed the middle-to-longwave-sensitive (L) opsin, and a 6-16% minority expressed the shortwave-sensitive (S) opsin. In both species the densities of L and S cones were higher in ventral than in dorsal retina. In both species the tuning-relevant amino acids of the S opsin indicate sensitivity in the near UV rather than the blue/violet range. Photopic spectral electroretinograms were recorded. Unexpectedly, their sensitivity profiles were best fitted by the linear summation of three visual pigment templates with lambda(max) at 370 nm (S pigment, UV), at 510 nm (L pigment), and at 450 nm (an as-yet unexplained mechanism). Avoiding predators and selecting food during the brief aboveground excursions may have exerted pressure to retain robust cone-based vision in Ctenomys. UV tuning of the S cone pigment is shared with a number of other hystricomorphs.
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Affiliation(s)
- Cristian E Schleich
- Laboratorio Ecofisiología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina.
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McMullen CA, Andrade FH, Crish SD. Underdeveloped extraocular muscles in the naked mole-rat (Heterocephalus glaber). Anat Rec (Hoboken) 2010; 293:918-23. [PMID: 20186962 DOI: 10.1002/ar.21107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The extraocular muscles (EOM), the effector arm of the ocular motor system, have a unique embryological origin and phenotype. The naked mole-rat (NMR) is a subterranean rodent with an underdeveloped visual system. It has not been established if their ocular motor system is also less developed. The NMR is an ideal model to examine the potential codependence of oculomotor and visual system development and evolution. Our goal was to compare the structural features of NMR EOMs to those of the mouse, a similar sized rodent with a fully developed visual system. Perfusion-fixed whole orbits and EOMs were dissected from adult NMR and C57BL mice and examined by light and electron microscopy. NMR orbital anatomy showed smaller EOMs in roughly the same distribution around the eye as in mouse and surrounded by a very small Harderian gland. The NMR EOMs did not appear to have the two-layer fiber distribution seen in mouse EOMs; fibers were also significantly smaller (112.3 +/- 46.2 vs. 550.7 +/- 226 sq microm in mouse EOMs, *P < 0.05). Myofibrillar density was less in NMR EOMs, and triad and other membranous structures were rudimentary. Finally, mitochondrial volume density was significantly less in NMR EOMs than in mouse EOM (4.5% +/- 1.9 vs. 21.2% +/- 11.6, respectively, *P < 0.05). These results demonstrate that NMR EOMs are smaller and less organized than those in the mouse. The "simpler" EOM organization and structure in NMR may be explained by the poor visual ability of these rodents, initially demonstrated by their primitive visual system.
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Affiliation(s)
- Colleen A McMullen
- Departments of Physiology, University of Kentucky, Lexington, Kentucky, USA.
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Kott O, Šumbera R, Němec P. Light perception in two strictly subterranean rodents: life in the dark or blue? PLoS One 2010; 5:e11810. [PMID: 20676369 PMCID: PMC2911378 DOI: 10.1371/journal.pone.0011810] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 06/23/2010] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND The African mole-rats (Bathyergidae, Rodentia) are strictly subterranean, congenitally microphthalmic rodents that are hardly ever exposed to environmental light. Because of the lack of an overt behavioural reaction to light, they have long been considered to be blind. However, recent anatomical studies have suggested retention of basic visual capabilities. In this study, we employed behavioural tests to find out if two mole-rat species are able to discriminate between light and dark, if they are able to discriminate colours and, finally, if the presence of light in burrows provokes plugging behaviour, which is assumed to have a primarily anti-predatory function. METHODOLOGY/PRINCIPAL FINDING We used a binary choice test to show that the silvery mole-rat Heliophobius argenteocinereus and the giant mole-rat Fukomys mechowii exhibit a clear photoavoidance response to full-spectrum ("white"), blue and green-yellow light, but no significant reaction to ultraviolet or red light during nest building. The mole-rats thus retain dark/light discrimination capabilities and a capacity to perceive short to medium-wavelength light in the photopic range of intensities. These findings further suggest that the mole-rat S opsin has its absorption maximum in the violet/blue part of the spectrum. The assay did not yield conclusive evidence regarding colour discrimination. To test the putative role of vision in bathyergid anti-predatory behaviour, we examined the reaction of mole-rats to the incidence of light in an artificial burrow system. The presence of light in the burrow effectively induced plugging of the illuminated tunnel. CONCLUSION/SIGNIFICANCE Our findings suggest that the photopic vision is conserved and that low acuity residual vision plays an important role in predator avoidance and tunnel maintenance in the African mole-rats.
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Affiliation(s)
- Ondřej Kott
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Pavel Němec
- Department of Zoology, Faculty of Science, Charles University in Prague, Prague, Czech Republic
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Rosen GJ, de Vries GJ, Goldman SL, Goldman BD, Forger NG. Distribution of oxytocin in the brain of a eusocial rodent. Neuroscience 2008; 155:809-17. [PMID: 18582538 DOI: 10.1016/j.neuroscience.2008.05.039] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 05/29/2008] [Accepted: 05/30/2008] [Indexed: 11/16/2022]
Abstract
Naked mole-rats are highly social rodents that live in large colonies characterized by a rigid social and reproductive hierarchy. Only one female, the queen, breeds. Most colony members are non-reproductive subordinates that work cooperatively to rear the young and maintain an underground burrow system. Little is known about the neurobiological basis of the complex sociality exhibited by this species. The neuropeptide oxytocin (Oxt) modulates social bonding and other social behaviors in many vertebrates. Here we examined the distribution of Oxt immunoreactivity in the brains of male and female naked mole-rats. As in other species, the majority of Oxt-immunoreactive (Oxt-ir) cells were found in the paraventricular and supraoptic nuclei, with additional labeled cells scattered throughout the preoptic and anterior hypothalamic areas. Oxt-ir fibers were found traveling toward and through the median eminence, as well as in the tenia tecta, septum, and nucleus of the diagonal band of Broca. A moderate network of fibers covered the bed nucleus of the stria terminalis and preoptic area, and a particularly dense fiber innervation of the nucleus accumbens and substantia innominata was observed. In the brainstem, Oxt-ir fibers were found in the periaqueductal gray, locus coeruleus, parabrachial nucleus, nucleus of the solitary tract, and nucleus ambiguus. The high levels of Oxt immunoreactivity in the nucleus accumbens and preoptic area are intriguing, given the link in other rodents between Oxt signaling in these regions and maternal behavior. Although only the queen gives birth or nurses pups in a naked mole-rat colony, most individuals actively participate in pup care.
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Affiliation(s)
- G J Rosen
- Department of Psychology and Center for Neuroendocrine Studies, Tobin Hall, University of Massachusetts, Amherst, MA 01003, USA
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45
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Evaluation of the retina and optic nerve in a rat model of chronic glaucoma using in vivo manganese-enhanced magnetic resonance imaging. Neuroimage 2008; 40:1166-74. [DOI: 10.1016/j.neuroimage.2008.01.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 12/21/2007] [Accepted: 01/05/2008] [Indexed: 11/19/2022] Open
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46
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Nemec P, Cveková P, Benada O, Wielkopolska E, Olkowicz S, Turlejski K, Burda H, Bennett NC, Peichl L. The visual system in subterranean African mole-rats (Rodentia, Bathyergidae): retina, subcortical visual nuclei and primary visual cortex. Brain Res Bull 2007; 75:356-64. [PMID: 18331898 DOI: 10.1016/j.brainresbull.2007.10.055] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Accepted: 10/17/2007] [Indexed: 10/22/2022]
Abstract
We have studied the visual system of subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seem of little importance. The eye diameter varies between 3.5mm in Bathyergus suillus and 1.3mm in Heterocephalus glaber. The small superficial eyes have features typical of sighted animals (clear optics, well-developed pupil and well-organized retina) and appear suited for proper image formation. The retinae are rod-dominated but possess rather high cone proportions of about 10%. The total number of retinal ganglion cells and optic nerve fibres ranges between 6000 in Bathyergus suillus and 2100 in Heliophobius argenteocinereus. Visual acuity (estimated from counts of peak ganglion cell density and axial length of the eye) is low, ranging between 0.3 and 0.5 cycles/degree. The retina projects to all the visual structures described in surface-dwelling sighted rodents. The suprachiasmatic nucleus is large and receives bilateral retinal input. All other visual nuclei are reduced in size and receive almost exclusively contralateral retinal projections of varying magnitude. The primary visual cortex is small and, in comparison to other rodents, displaced laterally. In conclusion, the African mole-rats possess relatively well-developed functional visual subsystems involved in photoperiodicity, form and brightness discrimination. In contrast, visual subsystems involved in coordination of visuomotor reflexes are severely reduced. This pattern suggests the retention of basic visual capabilities. Residual vision may enable subterranean mammals to localize breaches in the burrows that let in light thus providing a cue to enable mole-rats to reseal such entry points and to prevent entry of predators.
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Affiliation(s)
- Pavel Nemec
- Department of Zoology, Charles University, Vinicná 7, CZ-128 44 Praha 2, Czech Republic.
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Crish SD, Dengler-Crish CM, Catania KC. Central visual system of the naked mole-rat (Heterocephalus glaber). ACTA ACUST UNITED AC 2006; 288:205-12. [PMID: 16419086 DOI: 10.1002/ar.a.20288] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Naked mole-rats are fossorial rodents native to eastern Africa that spend their lives in extensive subterranean burrows where visual cues are poor. Not surprisingly, they have a degenerated eye and optic nerve, suggesting they have poor visual abilities. However, little is known about their central visual system. To investigate the organization of their central visual system, we injected a neuronal tracer into the eyes of naked mole-rats and mice to compare the neural structures mediating vision. We found that the superior colliculus and lateral geniculate nucleus were severely atrophied in the naked mole-rat. The olivary pretectal nucleus was reduced but still retained its characteristic morphology, possibly indicating a role in light detection. In addition, the suprachiasmatic nucleus is well innervated and resembles the same structure in other rodents. The naked mole-rat appears to have selectively lost structures that mediate form vision while retaining structures needed for minimal entrainment of circadian rhythms. Similar results have been reported for other mole-rat species. Taken together, these data suggest that light detection may still play an important role in the lives of these "blind" animals: most likely for circadian entrainment or setting seasonal rhythms.
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Affiliation(s)
- Samuel D Crish
- Department of Biological Sciences and Neuroscience Program, Vanderbilt University, Nashville, Tennessee 37235, USA
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Xiao J, Levitt JB, Buffenstein R. The use of a novel and simple method of revealing neural fibers to show the regression of the lateral geniculate nucleus in the naked mole-rat (Heterocephalus glaber). Brain Res 2006; 1077:81-9. [PMID: 16483554 DOI: 10.1016/j.brainres.2006.01.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 01/03/2006] [Accepted: 01/06/2006] [Indexed: 11/25/2022]
Abstract
The lateral geniculate nucleus (LG) is an important subcortical nucleus in the visual system. It receives primary projections from the retina and relays these to central visual structures. Although there are studies on the retina and visual cortex of animals with regressed vision, little is known about the LG in such animals. The strictly subterranean naked mole-rat (Heterocephalus glaber) has markedly reduced visual acuity with concomitant pronounced changes in the visual cortex. We used a novel method to reveal myelinated neural fibers in a histological study assessing if the LG shows regressive changes commensurate with the level of reliance on vision by this rodent. Myelin detection here relies on significant differences in visible light reflection between neural fibers and the gray matter. Moreover, this simple method does not interfere with further staining for additional analyses. This method reveals that the contribution of the LG to brain volume in the naked mole-rat is less than a third of that of the rat. This shows that the retinogeniculocortical system in the naked mole-rat is considerably smaller than that of rodents that rely heavily on their visual system, but is nevertheless less regressed than that of the extensively studied blind mole-rat; this may facilitate limited responses to visual stimuli.
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Affiliation(s)
- Jun Xiao
- Biology Department, The City College of New York, 138th Street and Convent Avenue, New York, NY 10031, USA.
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49
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Crish SD, Dengler-Crish CM, Comer CM. Population coding strategies and involvement of the superior colliculus in the tactile orienting behavior of naked mole-rats. Neuroscience 2006; 139:1461-6. [PMID: 16603320 DOI: 10.1016/j.neuroscience.2005.11.073] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2005] [Revised: 11/14/2005] [Accepted: 11/20/2005] [Indexed: 11/20/2022]
Abstract
Even simple behaviors of vertebrates are typically generated by the concerted action of large numbers of brain cells. However, the mechanisms by which groups of neurons work together as functional populations to guide behavior remain largely unknown. One of the major model systems for exploring these mechanisms has been mammalian visuomotor behavior. We describe here experiments that establish a new model system for analyzing the sensory control of behavior by neuronal populations using a mammalian somatosensory response: orientation to touch cues in a rodent. We found that the CNS mechanisms used to direct these orientation responses to touch can be delineated from behavioral experiments. In this study we demonstrate that the superior colliculus, a component of the vertebrate midbrain most often thought of as a visual structure, is an essential component of the naked mole-rat's unique tactile orienting behavior. Furthermore, the information processing that underlies this behavior displays striking parallels with that used for visual orientation at anatomical and computational levels.
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Affiliation(s)
- S D Crish
- Laboratory of Integrative Neuroscience, and Department of Biological Sciences, University of Illinois at Chicago, 60607, USA.
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50
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Xiao J, Levitt JB, Buffenstein R. A stereotaxic atlas of the brain of the naked mole-rat (Heterocephalus glaber). Neuroscience 2006; 141:1415-35. [PMID: 16793211 DOI: 10.1016/j.neuroscience.2006.03.077] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 03/27/2006] [Accepted: 03/27/2006] [Indexed: 10/24/2022]
Abstract
The naked mole-rat (Rodentia, Bathyergidae: Heterocephalus glaber) is a strictly subterranean eusocial mammal. These rodents show a suite of morphological and physiological adaptations, including brain specializations, to this underground milieu that they have inhabited since the early Miocene. Recently, naked mole-rats have received considerable attention as the longest living rodent known, and some of these brain specializations may be potentially important to their exceptional longevity. To serve as a basis for future brain studies, we have constructed a stereotaxic atlas of the brain of this species, labeling all major brain structures.
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Affiliation(s)
- J Xiao
- Department of Biology J526, City College of the City University of New York, 138th Street and Convent Avenue, New York, NY 10031, USA
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