1
|
Taylor A, Prasad A, Mueller RL. Amphibian Segmentation Clock Models Suggest How Large Genome and Cell Sizes Slow Developmental Rate. Integr Org Biol 2024; 6:obae021. [PMID: 39006893 PMCID: PMC11245677 DOI: 10.1093/iob/obae021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/20/2024] [Accepted: 06/18/2024] [Indexed: 07/16/2024] Open
Abstract
Evolutionary increases in genome size, cell volume, and nuclear volume have been observed across the tree of life, with positive correlations documented between all three traits. Developmental tempo slows as genomes, nuclei, and cells increase in size, yet the driving mechanisms are poorly understood. To bridge this gap, we use a mathematical model of the somitogenesis clock to link slowed developmental tempo with changes in intra-cellular gene expression kinetics induced by increasing genome size and nuclear volume. We adapt a well-known somitogenesis clock model to two model amphibian species that vary 10-fold in genome size: Xenopus laevis (3.1 Gb) and Ambystoma mexicanum (32 Gb). Based on simulations and backed by analytical derivations, we identify parameter changes originating from increased genome and nuclear size that slow gene expression kinetics. We simulate biological scenarios for which these parameter changes mathematically recapitulate slowed gene expression in A. mexicanum relative to X. laevis, and we consider scenarios for which additional alterations in gene product stability and chromatin packing are necessary. Results suggest that slowed degradation rates as well as changes induced by increasing nuclear volume and intron length, which remain relatively unexplored, are significant drivers of slowed developmental tempo.
Collapse
Affiliation(s)
- A Taylor
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - A Prasad
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO 80523, USA
| | - R Lockridge Mueller
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| |
Collapse
|
2
|
Small CD, Benfey TJ, Crawford BD. Tissue-specific compensatory mechanisms maintain tissue architecture and body size independent of cell size in polyploid zebrafish. Dev Biol 2024; 509:85-96. [PMID: 38387487 DOI: 10.1016/j.ydbio.2024.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/01/2024] [Accepted: 02/13/2024] [Indexed: 02/24/2024]
Abstract
Genome duplications and ploidy transitions have occurred in nearly every major taxon of eukaryotes, but they are far more common in plants than in animals. Due to the conservation of the nuclear:cytoplasmic volume ratio increased DNA content results in larger cells. In plants, polyploid organisms are larger than diploids as cell number remains relatively constant. Conversely, vertebrate body size does not correlate with cell size and ploidy as vertebrates compensate for increased cell size to maintain tissue architecture and body size. This has historically been explained by a simple reduction in cell number that matches the increase in cell size maintaining body size as ploidy increases, but here we show that the compensatory mechanisms that maintain body size in triploid zebrafish are tissue-specific: A) erythrocytes respond in the classical pattern with a reduced number of larger erythrocytes in circulation, B) muscle, a tissue comprised of polynucleated muscle fibers, compensates by reducing the number of larger nuclei such that myofiber and myotome size in unaffected by ploidy, and C) vascular tissue compensates by thickening blood vessel walls, possibly at the expense of luminal diameter. Understanding the physiological implications of ploidy on tissue function requires a detailed description of the specific mechanisms of morphological compensation occurring in each tissue to understand how ploidy changes affect development and physiology.
Collapse
Affiliation(s)
- C D Small
- Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, USA
| | - T J Benfey
- Biology Department, University of New Brunswick, Fredericton, NB, Canada
| | - B D Crawford
- Biology Department, University of New Brunswick, Fredericton, NB, Canada.
| |
Collapse
|
3
|
Huggenberger S, Walkowiak W. Evolution of air-borne vocalization: Insights from neural studies in the archeobatrachian species Bombina orientalis. J Comp Neurol 2024; 532:e25601. [PMID: 38450738 DOI: 10.1002/cne.25601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 01/30/2024] [Accepted: 02/23/2024] [Indexed: 03/08/2024]
Abstract
Vocalization of tetrapods evolved as an air-driven mechanism. Thus, it is conceivable that the underlaying neural network might have evolved from more ancient respiratory circuits and be made up of homologous components that generate breathing rhythms across vertebrates. In this context, the extant species of stem anurans provide an opportunity to analyze the connection of the neural circuits of lung ventilation and vocalization. Here, we analyzed the fictive lung ventilation and vocalization behavior of isolated brains of the Chinese fire-bellied toad Bombina orientalis during their mating season by nerve root recordings. We discovered significant differences in durations of activation of male brains after stimulation of the statoacoustic nerve or vocalization-relevant forebrain structures in comparison to female brains. The increased durations of motor nerve activities in male brains can be interpreted as fictive calling, as male's advertisement calls in vivo had the same general pattern compared to lung ventilation, but longer duration periods. Female brains react to the corresponding stimulations with the same shorter activity pattern that occurred spontaneously in both female and male brains and thus can be interpreted as fictive lung ventilations. These results support the hypothesis that vocal circuits evolved from ancient respiration networks in the anuran caudal hindbrain. Moreover, we could show that the terrestrial stem archeobatrachian Bombina spec. is an appropriate model to study the function and evolution of the shared network of lung ventilation and vocal generation.
Collapse
Affiliation(s)
- Stefan Huggenberger
- Institute of Anatomy and Clinical Morphology, Witten/Herdecke University, Witten, Germany
- Institute for Zoology, University of Cologne, Cologne, Germany
| | | |
Collapse
|
4
|
Chen P, Levy DL. Regulation of organelle size and organization during development. Semin Cell Dev Biol 2023; 133:53-64. [PMID: 35148938 PMCID: PMC9357868 DOI: 10.1016/j.semcdb.2022.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 01/20/2022] [Accepted: 02/01/2022] [Indexed: 12/11/2022]
Abstract
During early embryogenesis, as cells divide in the developing embryo, the size of intracellular organelles generally decreases to scale with the decrease in overall cell size. Organelle size scaling is thought to be important to establish and maintain proper cellular function, and defective scaling may lead to impaired development and disease. However, how the cell regulates organelle size and organization are largely unanswered questions. In this review, we summarize the process of size scaling at both the cell and organelle levels and discuss recently discovered mechanisms that regulate this process during early embryogenesis. In addition, we describe how some recently developed techniques and Xenopus as an animal model can be used to investigate the underlying mechanisms of size regulation and to uncover the significance of proper organelle size scaling and organization.
Collapse
Affiliation(s)
- Pan Chen
- Institute of Biochemistry and Molecular Biology, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, China.
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
| |
Collapse
|
5
|
Pincheira‐Donoso D, Harvey LP, Johnson JV, Hudson D, Finn C, Goodyear LEB, Guirguis J, Hyland EM, Hodgson DJ. Genome size does not influence extinction risk in the world's amphibians. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
| | - Lilly P. Harvey
- School of Science and Technology Nottingham Trent University Nottingham UK
| | - Jack V. Johnson
- School of Biological Sciences Queen's University Belfast Belfast UK
| | - Dave Hudson
- Centre for Ecology and Conservation, College of Life and Environmental Sciences University of Exeter Penryn UK
| | - Catherine Finn
- School of Biological Sciences Queen's University Belfast Belfast UK
| | | | - Jacinta Guirguis
- School of Biological Sciences Queen's University Belfast Belfast UK
| | - Edel M. Hyland
- School of Biological Sciences Queen's University Belfast Belfast UK
| | - Dave J. Hodgson
- Centre for Ecology and Conservation, College of Life and Environmental Sciences University of Exeter Penryn UK
| |
Collapse
|
6
|
Wei X, Fu S, Li H, Liu Y, Wang S, Feng W, Yang Y, Liu X, Zeng YY, Cheng M, Lai Y, Qiu X, Wu L, Zhang N, Jiang Y, Xu J, Su X, Peng C, Han L, Lou WPK, Liu C, Yuan Y, Ma K, Yang T, Pan X, Gao S, Chen A, Esteban MA, Yang H, Wang J, Fan G, Liu L, Chen L, Xu X, Fei JF, Gu Y. Single-cell Stereo-seq reveals induced progenitor cells involved in axolotl brain regeneration. Science 2022; 377:eabp9444. [PMID: 36048929 DOI: 10.1126/science.abp9444] [Citation(s) in RCA: 82] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The molecular mechanism underlying brain regeneration in vertebrates remains elusive. We performed spatial enhanced resolution omics sequencing (Stereo-seq) to capture spatially resolved single-cell transcriptomes of axolotl telencephalon sections during development and regeneration. Annotated cell types exhibited distinct spatial distribution, molecular features, and functions. We identified an injury-induced ependymoglial cell cluster at the wound site as a progenitor cell population for the potential replenishment of lost neurons, through a cell state transition process resembling neurogenesis during development. Transcriptome comparisons indicated that these induced cells may originate from local resident ependymoglial cells. We further uncovered spatially defined neurons at the lesion site that may regress to an immature neuron-like state. Our work establishes spatial transcriptome profiles of an anamniote tetrapod brain and decodes potential neurogenesis from ependymoglial cells for development and regeneration, thus providing mechanistic insights into vertebrate brain regeneration.
Collapse
Affiliation(s)
- Xiaoyu Wei
- BGI-Hangzhou, Hangzhou 310012, China.,BGI-Shenzhen, Shenzhen 518103, China
| | - Sulei Fu
- Department of Pathology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China.,Key Laboratory of Brain, Cognition and Education Sciences, Ministry of Education, Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou 510631, China
| | - Hanbo Li
- BGI-Shenzhen, Shenzhen 518103, China.,BGI-Qingdao, Qingdao 266555, China.,Lars Bolund Institute of Regenerative Medicine, Qingdao-Europe Advanced Institute for Life Sciences, BGI-Qingdao, Qingdao 266555, China
| | - Yang Liu
- BGI-Shenzhen, Shenzhen 518103, China
| | - Shuai Wang
- BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Weimin Feng
- BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yunzhi Yang
- BGI College & Henan Institute of Medical and Pharmaceutical Sciences, Zhengzhou University, Zhengzhou 450000, China
| | | | - Yan-Yun Zeng
- Department of Pathology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China.,Key Laboratory of Brain, Cognition and Education Sciences, Ministry of Education, Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou 510631, China
| | - Mengnan Cheng
- BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yiwei Lai
- Laboratory of Integrative Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Xiaojie Qiu
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Liang Wu
- BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | | | - Yujia Jiang
- BGI-Shenzhen, Shenzhen 518103, China.,BGI College & Henan Institute of Medical and Pharmaceutical Sciences, Zhengzhou University, Zhengzhou 450000, China
| | - Jiangshan Xu
- BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | | | - Cheng Peng
- Department of Pathology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China.,Key Laboratory of Brain, Cognition and Education Sciences, Ministry of Education, Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou 510631, China
| | - Lei Han
- BGI-Shenzhen, Shenzhen 518103, China.,Shenzhen Key Laboratory of Single-Cell Omics, BGI-Shenzhen, Shenzhen 518120, China.,Shenzhen Bay Laboratory, Shenzhen 518000, China
| | - Wilson Pak-Kin Lou
- Department of Pathology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China.,Key Laboratory of Brain, Cognition and Education Sciences, Ministry of Education, Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou 510631, China
| | - Chuanyu Liu
- BGI-Shenzhen, Shenzhen 518103, China.,Shenzhen Bay Laboratory, Shenzhen 518000, China
| | - Yue Yuan
- BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | | | - Tao Yang
- BGI-Shenzhen, Shenzhen 518103, China
| | - Xiangyu Pan
- Department of Pathology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China
| | | | - Ao Chen
- BGI-Shenzhen, Shenzhen 518103, China.,Department of Biology, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Miguel A Esteban
- Laboratory of Integrative Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Institute of Stem Cells and Regeneration, Chinese Academy of Sciences, Beijing 100101, China
| | - Huanming Yang
- BGI-Shenzhen, Shenzhen 518103, China.,James D. Watson Institute of Genome Sciences, Hangzhou 310058, China
| | - Jian Wang
- BGI-Shenzhen, Shenzhen 518103, China.,James D. Watson Institute of Genome Sciences, Hangzhou 310058, China
| | | | - Longqi Liu
- BGI-Hangzhou, Hangzhou 310012, China.,BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.,Shenzhen Bay Laboratory, Shenzhen 518000, China
| | - Liang Chen
- Hubei Key Laboratory of Cell Homeostasis, RNA Institute, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Xun Xu
- BGI-Shenzhen, Shenzhen 518103, China.,Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen 518120, China
| | - Ji-Feng Fei
- Department of Pathology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou 510080, China
| | - Ying Gu
- BGI-Hangzhou, Hangzhou 310012, China.,BGI-Shenzhen, Shenzhen 518103, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.,Guangdong Provincial Key Laboratory of Genome Read and Write, BGI-Shenzhen, Shenzhen 518120, China
| |
Collapse
|
7
|
Itgen MW, Natalie GR, Siegel DS, Sessions SK, Mueller RL. Genome size drives morphological evolution in organ-specific ways. Evolution 2022; 76:1453-1468. [PMID: 35657770 PMCID: PMC9545640 DOI: 10.1111/evo.14519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 03/23/2022] [Accepted: 04/11/2022] [Indexed: 01/22/2023]
Abstract
Morphogenesis is an emergent property of biochemical and cellular interactions during development. Genome size and the correlated trait of cell size can influence these interactions through effects on developmental rate and tissue geometry, ultimately driving the evolution of morphology. We tested whether variation in genome and body size is related to morphological variation in the heart and liver using nine species of the salamander genus Plethodon (genome sizes 29-67 gigabases). Our results show that overall organ size is a function of body size, whereas tissue structure changes dramatically with evolutionary increases in genome size. In the heart, increased genome size is correlated with a reduction of myocardia in the ventricle, yielding proportionally less force-producing mass and greater intertrabecular space. In the liver, increased genome size is correlated with fewer and larger vascular structures, positioning hepatocytes farther from the circulatory vessels that transport key metabolites. Although these structural changes should have obvious impacts on organ function, their effects on organismal performance and fitness may be negligible because low metabolic rates in salamanders relax selective pressure on function of key metabolic organs. Overall, this study suggests large genome and cell size influence the developmental systems involved in heart and liver morphogenesis.
Collapse
Affiliation(s)
- Michael W. Itgen
- Department of BiologyColorado State UniversityFort CollinsColorado80523USA
| | | | - Dustin S. Siegel
- Department of BiologySoutheast Missouri State UniversityCape GirardeauMissouri63701USA
| | | | | |
Collapse
|
8
|
Abstract
The ability to sense and localize sound is so advantageous for survival that it is difficult to understand the almost 100 million year gap separating the appearance of early tetrapods and the emergence of an impedance-matching tympanic middle ear - which we normally regard as a prerequisite for sensitive hearing on land - in their descendants. Recent studies of hearing in extant atympanate vertebrates have provided significant insights into the ancestral state(s) and the early evolution of the terrestrial tetrapod auditory system. These reveal a mechanism for sound pressure detection and directional hearing in 'earless' atympanate vertebrates that may be generalizable to all tetrapods, including the earliest terrestrial species. Here, we review the structure and function of vertebrate tympanic middle ears and highlight the multiple acquisition and loss events that characterize the complex evolutionary history of this important sensory structure. We describe extratympanic pathways for sound transmission to the inner ear and synthesize findings from recent studies to propose a general mechanism for hearing in 'earless' atympanate vertebrates. Finally, we integrate these studies with research on tympanate species that may also rely on extratympanic mechanisms for acoustic reception of infrasound (<20 Hz) and with studies on human bone conduction mechanisms of hearing.
Collapse
Affiliation(s)
- Grace Capshaw
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | | | - Catherine E. Carr
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| |
Collapse
|
9
|
Gerhardt HC, Tucker MA, von Twickel A, Walkowiak W. Anuran Vocal Communication: Effects of Genome Size, Cell Number and Cell Size. BRAIN, BEHAVIOR AND EVOLUTION 2021; 96:137-146. [PMID: 34788770 DOI: 10.1159/000520913] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 11/06/2021] [Indexed: 11/19/2022]
Abstract
Significant variation in genome size occurs among anuran amphibians and can affect cell size and number. In the gray treefrog complex in North America increases in cell size in autotriploids of the diploid (Hyla chrysoscelis) altered the temporal structure of mate-attracting vocalizations and auditory selectivity for these properties. Here we show that the tetraploid species (Hyla versicolor) also has significantly fewer brain neurons than H. chrysoscelis. With regard to cell size in tissues involved in vocal communication, spinal motor neurons were larger in tetraploids than in diploids and comparable to differences in erythrocyte size; smaller increases were found in one of the three auditory centers in the torus semicircularis. Future studies should address questions about how environmental conditions during development affect cell numbers and size and the causal relationships between these cellular changes and the vocal communication system.
Collapse
Affiliation(s)
- H Carl Gerhardt
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, USA
| | - Mitch A Tucker
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, USA
| | | | | |
Collapse
|
10
|
Recovery-from-extinction effects in an anuran amphibian: renewal effect, but no reinstatement. Anim Cogn 2021; 25:359-368. [PMID: 34468877 DOI: 10.1007/s10071-021-01558-5] [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] [Received: 08/21/2020] [Revised: 08/25/2021] [Accepted: 08/27/2021] [Indexed: 10/20/2022]
Abstract
Recovery-from-extinction effects in which a conditioned response returns after extinction have been shown in mammals, birds and fish. Thus, these effects appear to be conserved among vertebrates; however, they have yet to be investigated in amphibians. Using prey catching conditioning in the fire-bellied toad (Bombina orientalis), we tested if renewal and reinstatement occurred after extinction when subjects were respectively re-exposed to the context or reinforcer used during conditioning. For renewal, a different context was used during extinction and thus renewal tests assessed if external contextual cues associated during conditioning stimulated prey catching performance. For reinstatement, the reinforcer withheld during extinction was simply delivered again prior to a test assessing if internal cues associated with recent prey consumption stimulated prey catching performance. Conditioning followed a fixed ratio 5 schedule of reinforcement, where five attempts to capture a cricket stimulus displayed on a computer screen were reinforced by delivery of a single live cricket. Performance was measured as the time to reach five prey catching attempts. A significant improvement in prey catching performance during conditioning followed by deterioration with extinction was seen in the experiments. Upon return to the context used for conditioning after extinction, toads showed a renewal effect whereby they displayed faster performance during testing compared to the end of extinction. Conversely, toads showed no reinstatement effect because pre-feeding of a cricket did not influence performance during the test that followed extinction. Reinstatement could have been lost in amphibian phylogeny due to secondary simplification of the nervous system.
Collapse
|
11
|
Small CD, Davis JP, Crawford BD, Benfey TJ. Early, nonlethal ploidy and genome size quantification using confocal microscopy in zebrafish embryos. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2021; 336:496-510. [PMID: 34254444 DOI: 10.1002/jez.b.23069] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 05/12/2021] [Accepted: 06/17/2021] [Indexed: 11/07/2022]
Abstract
Ploidy transitions through whole genome duplication have shaped evolution by allowing the sub- and neo-functionalization of redundant copies of highly conserved genes to express novel traits. The nuclear:cytoplasmic (n:c) ratio is maintained in polyploid vertebrates resulting in larger cells, but body size is maintained by a concomitant reduction in cell number. Ploidy can be manipulated easily in most teleosts, and the zebrafish, already well established as a model system for biomedical research, is therefore an excellent system in which to study the effects of increased cell size and reduced cell numbers in polyploids on development and physiology. Here we describe a novel technique using confocal microscopy to measure genome size and determine ploidy non-lethally at 48 h post-fertilization (hpf) in transgenic zebrafish expressing fluorescent histones. Volumetric analysis of myofiber nuclei using open-source software can reliably distinguish diploids and triploids from a mixed-ploidy pool of embryos for subsequent experimentation. We present an example of this by comparing heart rate between confirmed diploid and triploid embryos at 54 hpf.
Collapse
Affiliation(s)
| | - James P Davis
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
| | - Bryan D Crawford
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
| | - Tillmann J Benfey
- Department of Biology, University of New Brunswick, Fredericton, NB, Canada
| |
Collapse
|
12
|
MRI- and histologically derived neuroanatomical atlas of the Ambystoma mexicanum (axolotl). Sci Rep 2021; 11:9850. [PMID: 33972650 PMCID: PMC8110773 DOI: 10.1038/s41598-021-89357-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 04/12/2021] [Indexed: 02/03/2023] Open
Abstract
Amphibians are an important vertebrate model system to understand anatomy, genetics and physiology. Importantly, the brain and spinal cord of adult urodels (salamanders) have an incredible regeneration capacity, contrary to anurans (frogs) and the rest of adult vertebrates. Among these amphibians, the axolotl (Ambystoma mexicanum) has gained most attention because of the surge in the understanding of central nervous system (CNS) regeneration and the recent sequencing of its whole genome. However, a complete comprehension of the brain anatomy is not available. In the present study we created a magnetic resonance imaging (MRI) atlas of the in vivo neuroanatomy of the juvenile axolotl brain. This is the first MRI atlas for this species and includes three levels: (1) 82 regions of interest (ROIs) and a version with 64 ROIs; (2) a division of the brain according to the embryological origin of the neural tube, and (3) left and right hemispheres. Additionally, we localized the myelin rich regions of the juvenile brain. The atlas, the template that the atlas was derived from, and a masking file, can be found on Zenodo at https://doi.org/10.5281/zenodo.4595016 . This MRI brain atlas aims to be an important tool for future research of the axolotl brain and that of other amphibians.
Collapse
|
13
|
Grigoryan EN. Study of Natural Longlife Juvenility and Tissue Regeneration in Caudate Amphibians and Potential Application of Resulting Data in Biomedicine. J Dev Biol 2021; 9:2. [PMID: 33477527 PMCID: PMC7838874 DOI: 10.3390/jdb9010002] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 01/07/2021] [Accepted: 01/12/2021] [Indexed: 12/14/2022] Open
Abstract
The review considers the molecular, cellular, organismal, and ontogenetic properties of Urodela that exhibit the highest regenerative abilities among tetrapods. The genome specifics and the expression of genes associated with cell plasticity are analyzed. The simplification of tissue structure is shown using the examples of the sensory retina and brain in mature Urodela. Cells of these and some other tissues are ready to initiate proliferation and manifest the plasticity of their phenotype as well as the correct integration into the pre-existing or de novo forming tissue structure. Without excluding other factors that determine regeneration, the pedomorphosis and juvenile properties, identified on different levels of Urodele amphibians, are assumed to be the main explanation for their high regenerative abilities. These properties, being fundamental for tissue regeneration, have been lost by amniotes. Experiments aimed at mammalian cell rejuvenation currently use various approaches. They include, in particular, methods that use secretomes from regenerating tissues of caudate amphibians and fish for inducing regenerative responses of cells. Such an approach, along with those developed on the basis of knowledge about the molecular and genetic nature and age dependence of regeneration, may become one more step in the development of regenerative medicine.
Collapse
Affiliation(s)
- Eleonora N Grigoryan
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
| |
Collapse
|
14
|
Rozenblit F, Gollisch T. What the salamander eye has been telling the vision scientist's brain. Semin Cell Dev Biol 2020; 106:61-71. [PMID: 32359891 PMCID: PMC7493835 DOI: 10.1016/j.semcdb.2020.04.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/16/2020] [Accepted: 04/16/2020] [Indexed: 12/30/2022]
Abstract
Salamanders have been habitual residents of research laboratories for more than a century, and their history in science is tightly interwoven with vision research. Nevertheless, many vision scientists - even those working with salamanders - may be unaware of how much our knowledge about vision, and particularly the retina, has been shaped by studying salamanders. In this review, we take a tour through the salamander history in vision science, highlighting the main contributions of salamanders to our understanding of the vertebrate retina. We further point out specificities of the salamander visual system and discuss the perspectives of this animal system for future vision research.
Collapse
Affiliation(s)
- Fernando Rozenblit
- Department of Ophthalmology, University Medical Center Göttingen, 37073, Göttingen, Germany; Bernstein Center for Computational Neuroscience Göttingen, 37077, Göttingen, Germany
| | - Tim Gollisch
- Department of Ophthalmology, University Medical Center Göttingen, 37073, Göttingen, Germany; Bernstein Center for Computational Neuroscience Göttingen, 37077, Göttingen, Germany.
| |
Collapse
|
15
|
Miller KE, Brownlee C, Heald R. The power of amphibians to elucidate mechanisms of size control and scaling. Exp Cell Res 2020; 392:112036. [PMID: 32343955 PMCID: PMC7246146 DOI: 10.1016/j.yexcr.2020.112036] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 04/19/2020] [Accepted: 04/22/2020] [Indexed: 01/26/2023]
Abstract
Size is a fundamental feature of biology that affects physiology at all levels, from the organism to organs and tissues to cells and subcellular structures. How size is determined at these different levels, and how biological structures scale to fit together and function properly are important open questions. Historically, amphibian systems have been extremely valuable to describe scaling phenomena, as they occupy some of the extremes in biological size and are amenable to manipulations that alter genome and cell size. More recently, the application of biochemical, biophysical, and embryological techniques to amphibians has provided insight into the molecular mechanisms underlying scaling of subcellular structures to cell size, as well as how perturbation of normal size scaling impacts other aspects of cell and organism physiology.
Collapse
Affiliation(s)
- Kelly E Miller
- Department of Molecular and Cell Biology, University of California, CA, 94720, Berkeley, USA
| | - Christopher Brownlee
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY, 11794-8651, USA.
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, CA, 94720, Berkeley, USA.
| |
Collapse
|
16
|
Wesley CC, Mishra S, Levy DL. Organelle size scaling over embryonic development. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2020; 9:e376. [PMID: 32003549 DOI: 10.1002/wdev.376] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 12/19/2019] [Accepted: 01/08/2020] [Indexed: 12/13/2022]
Abstract
Cell division without growth results in progressive cell size reductions during early embryonic development. How do the sizes of intracellular structures and organelles scale with cell size and what are the functional implications of such scaling relationships? Model organisms, in particular Caenorhabditis elegans worms, Drosophila melanogaster flies, Xenopus laevis frogs, and Mus musculus mice, have provided insights into developmental size scaling of the nucleus, mitotic spindle, and chromosomes. Nuclear size is regulated by nucleocytoplasmic transport, nuclear envelope proteins, and the cytoskeleton. Regulators of microtubule dynamics and chromatin compaction modulate spindle and mitotic chromosome size scaling, respectively. Developmental scaling relationships for membrane-bound organelles, like the endoplasmic reticulum, Golgi, mitochondria, and lysosomes, have been less studied, although new imaging approaches promise to rectify this deficiency. While models that invoke limiting components and dynamic regulation of assembly and disassembly can account for some size scaling relationships in early embryos, it will be exciting to investigate the contribution of newer concepts in cell biology such as phase separation and interorganellar contacts. With a growing understanding of the underlying mechanisms of organelle size scaling, future studies promise to uncover the significance of proper scaling for cell function and embryonic development, as well as how aberrant scaling contributes to disease. This article is categorized under: Establishment of Spatial and Temporal Patterns > Regulation of Size, Proportion, and Timing Early Embryonic Development > Fertilization to Gastrulation Comparative Development and Evolution > Model Systems.
Collapse
Affiliation(s)
- Chase C Wesley
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| | - Sampada Mishra
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| |
Collapse
|
17
|
Abstract
The genetic control of the characteristic cell sizes of different species and tissues is a long-standing enigma. Plants are convenient for studying this question in a multicellular context, as their cells do not move and are easily tracked and measured from organ initiation in the meristems to subsequent morphogenesis and differentiation. In this article, we discuss cell size control in plants compared with other organisms. As seen from yeast cells to mammalian cells, size homeostasis is maintained cell autonomously in the shoot meristem. In developing organs, vacuolization contributes to cell size heterogeneity and may resolve conflicts between growth control at the cellular and organ levels. Molecular mechanisms for cell size control have implications for how cell size responds to changes in ploidy, which are particularly important in plant development and evolution. We also discuss comparatively the functional consequences of cell size and their potential repercussions at higher scales, including genome evolution.
Collapse
Affiliation(s)
- Marco D'Ario
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Robert Sablowski
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| |
Collapse
|
18
|
Womack MC, Metz MJ, Hoke KL. Larger Genomes Linked to Slower Development and Loss of Late-Developing Traits. Am Nat 2019; 194:854-864. [PMID: 31738099 DOI: 10.1086/705897] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Genome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel data set with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear. We established that genome size is negatively correlated with development rate across 90 anuran species and found that genome size evolution is correlated with evolutionary loss of the middle ear bone (columella) among 241 species (224 eared and 17 earless). We further tested whether the development of the tympanic middle ear could be constrained by large cell sizes and small body sizes during key stages of tympanic middle ear development (metamorphosis). Together, our evidence suggests that larger genomes, slower development rate, and smaller body sizes at metamorphosis may contribute to the loss of the anuran tympanic middle ear. We conclude that increases in anuran genome size, although less drastic than those in salamanders, may affect development of late-forming traits.
Collapse
|
19
|
Joven A, Simon A. Homeostatic and regenerative neurogenesis in salamanders. Prog Neurobiol 2018; 170:81-98. [PMID: 29654836 DOI: 10.1016/j.pneurobio.2018.04.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/20/2018] [Accepted: 04/07/2018] [Indexed: 01/02/2023]
Abstract
Large-scale regeneration in the adult central nervous system is a unique capacity of salamanders among tetrapods. Salamanders can replace neuronal populations, repair damaged nerve fibers and restore tissue architecture in retina, brain and spinal cord, leading to functional recovery. The underlying mechanisms have long been difficult to study due to the paucity of available genomic tools. Recent technological progress, such as genome sequencing, transgenesis and genome editing provide new momentum for systematic interrogation of regenerative processes in the salamander central nervous system. Understanding central nervous system regeneration also entails designing the appropriate molecular, cellular, and behavioral assays. Here we outline the organization of salamander brain structures. With special focus on ependymoglial cells, we integrate cellular and molecular processes of neurogenesis during developmental and adult homeostasis as well as in various injury models. Wherever possible, we correlate developmental and regenerative neurogenesis to the acquisition and recovery of behaviors. Throughout the review we place the findings into an evolutionary context for inter-species comparisons.
Collapse
Affiliation(s)
- Alberto Joven
- Department of Cell and Molecular Biology, Karolinska Institute, Berzelius väg 35, 17177, Stockholm, Sweden.
| | - András Simon
- Department of Cell and Molecular Biology, Karolinska Institute, Berzelius väg 35, 17177, Stockholm, Sweden.
| |
Collapse
|
20
|
Zhao CL, Jin L, Zhong MJ, Xie F, Jiang JP, Li DY, Liao WB. Cerebellum size is positively correlated with geographic distribution range in anurans. ANIM BIOL 2018. [DOI: 10.1163/15707563-17000121] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Abstract
The ‘cognitive buffer’ hypothesis predicts that the costs of relatively large brains are compensated for later in life by the increased benefits of large brains providing a higher chance of survival under changing environments through flexible behaviors in the animal kingdom. Thus, animals that live in a larger range (with a higher probability of environmental variation) are expected to have larger brains than those that live in a restricted geographic range. Here, to test the prediction of the ‘cognitive buffer’ hypothesis that larger brains should be expected to occur in species living in geographic ranges of larger size, we analyzed the relationship between the size of the geographic range and brain size and the size of various brain regions among 42 species of anurans using phylogenetic comparative methods. The results show that there is no correlation between relative brain size and size of the species’ geographic range when correcting for phylogenetic effects and body size. Our findings suggest that the effects of the cognitive buffer and the energetic constraints on brains result in non-significant variation in overall brain size. However, the geographic range is positively correlated with cerebellum size, but not with optic tecta, suggesting that species distributed in a wider geographic range do not exhibit larger optic tecta which would provide behavioral flexibility to allow for an early escape from potential predators and discovery of new food resources in unpredictable environments.
Collapse
Affiliation(s)
- Chun Lin Zhao
- 1Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China
| | - Long Jin
- 1Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China
| | - Mao Jun Zhong
- 1Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China
| | - Feng Xie
- 2Chengdu Institute Biology, Chinese Academy of Sciences, Chengdu 610041, Sichuan, China
| | - Jian Ping Jiang
- 2Chengdu Institute Biology, Chinese Academy of Sciences, Chengdu 610041, Sichuan, China
| | - Da Yong Li
- 1Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China
- 3Institute of Rare Animals and Plants, China West Normal University, Nanchong 637009, Sichuan, China
| | - Wen Bo Liao
- 1Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong 637009, Sichuan, China
- 3Institute of Rare Animals and Plants, China West Normal University, Nanchong 637009, Sichuan, China
| |
Collapse
|
21
|
Seligmann H, Warthi G. Genetic Code Optimization for Cotranslational Protein Folding: Codon Directional Asymmetry Correlates with Antiparallel Betasheets, tRNA Synthetase Classes. Comput Struct Biotechnol J 2017; 15:412-424. [PMID: 28924459 PMCID: PMC5591391 DOI: 10.1016/j.csbj.2017.08.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 07/20/2017] [Accepted: 08/05/2017] [Indexed: 12/14/2022] Open
Abstract
A new codon property, codon directional asymmetry in nucleotide content (CDA), reveals a biologically meaningful genetic code dimension: palindromic codons (first and last nucleotides identical, codon structure XZX) are symmetric (CDA = 0), codons with structures ZXX/XXZ are 5'/3' asymmetric (CDA = - 1/1; CDA = - 0.5/0.5 if Z and X are both purines or both pyrimidines, assigning negative/positive (-/+) signs is an arbitrary convention). Negative/positive CDAs associate with (a) Fujimoto's tetrahedral codon stereo-table; (b) tRNA synthetase class I/II (aminoacylate the 2'/3' hydroxyl group of the tRNA's last ribose, respectively); and (c) high/low antiparallel (not parallel) betasheet conformation parameters. Preliminary results suggest CDA-whole organism associations (body temperature, developmental stability, lifespan). Presumably, CDA impacts spatial kinetics of codon-anticodon interactions, affecting cotranslational protein folding. Some synonymous codons have opposite CDA sign (alanine, leucine, serine, and valine), putatively explaining how synonymous mutations sometimes affect protein function. Correlations between CDA and tRNA synthetase classes are weaker than between CDA and antiparallel betasheet conformation parameters. This effect is stronger for mitochondrial genetic codes, and potentially drives mitochondrial codon-amino acid reassignments. CDA reveals information ruling nucleotide-protein relations embedded in reversed (not reverse-complement) sequences (5'-ZXX-3'/5'-XXZ-3').
Collapse
Affiliation(s)
- Hervé Seligmann
- Aix-Marseille Univ, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UM 63, CNRS UMR7278, IRD 198, INSERM U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Marseille, Postal code 13385, France
- Dept. Ecol Evol Behav, Alexander Silberman Inst Life Sci, The Hebrew University of Jerusalem, IL-91904 Jerusalem, Israel
| | - Ganesh Warthi
- Aix-Marseille Univ, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UM 63, CNRS UMR7278, IRD 198, INSERM U1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Marseille, Postal code 13385, France
| |
Collapse
|
22
|
Joven A, Wang H, Pinheiro T, Hameed LS, Belnoue L, Simon A. Cellular basis of brain maturation and acquisition of complex behaviors in salamanders. Development 2017; 145:dev.160051. [DOI: 10.1242/dev.160051] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 11/20/2017] [Indexed: 12/22/2022]
Abstract
The overall bauplan of the tetrapod brain is highly conserved, yet significant variations exist among species in terms of brain size, structural composition and cellular diversity. Understanding processes underlying neural and behavioral development in a wide range of species is important both from an evolutionary developmental perspective as well as for the identification of cell sources with post-developmental neurogenic potential. Here we characterize germinal processes in the brain of Notophthalmus viridescens and Pleurodeles waltl during both development and adulthood. Using a combination of cell tracking tools, including clonal analyses in new transgenic salamander lines we examine the origin of neural stem and progenitor cells found in the adult brain, determine regional variability in cell cycle length of progenitor cells, and show spatio-temporally orchestrated neurogenesis. We analyze how maturation of different brain regions and neuronal subpopulations are linked to the acquisition of complex behaviors, and how these behaviors are altered upon chemical ablation of dopamine neurons. Our data analyzed from an evolutionary perspective reveal both common and species-specific processes in tetrapod brain formation and function.
Collapse
Affiliation(s)
- Alberto Joven
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Heng Wang
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
- College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Tiago Pinheiro
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - L. Shahul Hameed
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Laure Belnoue
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - András Simon
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| |
Collapse
|
23
|
Roth G. Convergent evolution of complex brains and high intelligence. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0049. [PMID: 26554042 DOI: 10.1098/rstb.2015.0049] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Within the animal kingdom, complex brains and high intelligence have evolved several to many times independently, e.g. among ecdysozoans in some groups of insects (e.g. blattoid, dipteran, hymenopteran taxa), among lophotrochozoans in octopodid molluscs, among vertebrates in teleosts (e.g. cichlids), corvid and psittacid birds, and cetaceans, elephants and primates. High levels of intelligence are invariantly bound to multimodal centres such as the mushroom bodies in insects, the vertical lobe in octopodids, the pallium in birds and the cerebral cortex in primates, all of which contain highly ordered associative neuronal networks. The driving forces for high intelligence may vary among the mentioned taxa, e.g. needs for spatial learning and foraging strategies in insects and cephalopods, for social learning in cichlids, instrumental learning and spatial orientation in birds and social as well as instrumental learning in primates.
Collapse
Affiliation(s)
- Gerhard Roth
- Brain Research Institute, University of Bremen, 28334 Bremen, Germany
| |
Collapse
|
24
|
Abstract
Cells of a given type maintain a characteristic cell size to function efficiently in their ecological or organismal context. They achieve this through the regulation of growth rates or by actively sensing size and coupling this signal to cell division. We focus this review on potential size-sensing mechanisms, including geometric, external cue, and titration mechanisms. Mechanisms that titrate proteins against DNA are of particular interest because they are consistent with the robust correlation of DNA content and cell size. We review the literature, which suggests that titration mechanisms may underlie cell-size sensing in Xenopus embryos, budding yeast, and Escherichia coli, whereas alternative mechanisms may function in fission yeast.
Collapse
Affiliation(s)
- Amanda A Amodeo
- Department of Biology, Stanford University, Stanford, California 94305
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, California 94305
| |
Collapse
|
25
|
Levy DL, Heald R. Biological Scaling Problems and Solutions in Amphibians. Cold Spring Harb Perspect Biol 2015; 8:a019166. [PMID: 26261280 DOI: 10.1101/cshperspect.a019166] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Size is a primary feature of biological systems that varies at many levels, from the organism to its constituent cells and subcellular structures. Amphibians populate some of the extremes in biological size and have provided insight into scaling mechanisms, upper and lower size limits, and their physiological significance. Body size variation is a widespread evolutionary tactic among amphibians, with miniaturization frequently correlating with direct development that occurs without a tadpole stage. The large genomes of salamanders lead to large cell sizes that necessitate developmental modification and morphological simplification. Amphibian extremes at the cellular level have provided insight into mechanisms that accommodate cell-size differences. Finally, how organelles scale to cell size between species and during development has been investigated at the molecular level, because subcellular scaling can be recapitulated using Xenopus in vitro systems.
Collapse
Affiliation(s)
- Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Rebecca Heald
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720
| |
Collapse
|