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Arlegi M, Lorenzo C. Evolutionary selection and morphological integration in the hand of modern humans. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2024:e25024. [PMID: 39228137 DOI: 10.1002/ajpa.25024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2024] [Revised: 08/10/2024] [Accepted: 08/18/2024] [Indexed: 09/05/2024]
Abstract
OBJECTIVES To enhance our understanding of the evolutionary dynamics of the modern human hand by analyzing the degree of integration and ability to respond to selection pressures of each phalanx and metacarpal bone. MATERIALS AND METHODS The sample comprised 96 adult individuals, both female and male, from Euro-American, Afro-American, and European populations. We collected 10 linear measurements from the 19 metacarpals and proximal, middle, and distal phalanges that constitute the five digits of the hand. Using these data, we constructed variance/covariance matrices to quantify the degree of integration and assess the hand ability to respond to selective pressures. RESULTS Distal phalanges are the most evolvable and flexible elements, while being the least integrated and constrained. The thumb is similarly integrated as the second and third rays, while medial rays (fourth and fifth digits) are more integrated. However, the thumb presents different integration and response to selection patterns. No significant relationship was found between functionality and the indices of selection and integration. Finally, the correlation between hand and foot indices yielded significant results for conditional evolvability and flexibility. DISCUSSION The findings suggest different evolutionary trajectories for the metacarpal and distal phalanx in the modern human thumb, likely reflecting varying functional and developmental pressures. The first metacarpal, characterized by high flexibility and low evolvability, appears to have reached a stable, optimal morphology, under stabilizing selection. In contrast, the distal phalanx seems to have undergone directional evolution, suggesting specialization for a specific function. Comparisons between hands and feet suggest that these structures evolve differently under directional selection but similarly under stabilizing selection.
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Affiliation(s)
- Mikel Arlegi
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK
| | - Carlos Lorenzo
- Departament d'Història i Història de l'Art, Universitat Rovira i Virgili, Tarragona, Spain
- Institut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA), Tarragona, Spain
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Kjosness KM, Reno PL. Identifying the homology of the short human pisiform and its lost ossification center. EvoDevo 2019; 10:32. [PMID: 31788181 PMCID: PMC6876086 DOI: 10.1186/s13227-019-0145-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 11/05/2019] [Indexed: 01/14/2023] Open
Abstract
Background The pisiform and calcaneus are paralogous bones of the wrist and ankle and are the only carpal and tarsal, respectively, to develop from two ossification centers with an associated growth plate in mammals. Human pisiforms and calcanei have undergone drastic evolutionary changes since our last common ancestor with chimpanzees and bonobos. The human pisiform is truncated and has lost an ossification center with the associated growth plate, while the human calcaneus has expanded and retained two ossification centers and a growth plate. Mammalian pisiforms represent a wide range of morphologies but extremely short pisiforms are rare and ossification center loss is even rarer. This raises the question of whether the sole human pisiform ossification center is homologous to the primary center or the secondary center of other species. We performed an ontogenetic study of pisiform and calcaneus ossification patterns and timing in macaques, apes, and humans (n = 907) from museum skeletal collections to address this question. Results Human pisiforms ossify irregularly and lack characteristic features of other primates while they develop. Pisiform primary and secondary center ossification timing typically matches that of the calcaneus of non-human primates, while the human pisiform corresponds with calcaneal secondary center ossification. Finally, human pisiforms ossify at the same dental stages as pisiform and calcaneal secondary centers in other hominoids. Conclusions These data indicate that the human pisiform is homologous to the pisiform epiphysis of other species, and that humans have lost a primary ossification center and associated growth plate while retaining ossification timing of the secondary center. This represents an exceptional evolutionary event and demonstrates a profound developmental change in the human wrist that is unusual not only among primates, but among mammals.
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Affiliation(s)
- Kelsey M Kjosness
- Department of Bio-Medical Sciences, Philadelphia College of Osteopathic Medicine, 4170 City Avenue, Philadelphia, PA 19131 USA
| | - Philip L Reno
- Department of Bio-Medical Sciences, Philadelphia College of Osteopathic Medicine, 4170 City Avenue, Philadelphia, PA 19131 USA
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Matsuo K, Ji S, Miya A, Yoda M, Hamada Y, Tanaka T, Takao-Kawabata R, Kawaai K, Kuroda Y, Shibata S. Innervation of the tibial epiphysis through the intercondylar foramen. Bone 2019; 120:297-304. [PMID: 30439572 DOI: 10.1016/j.bone.2018.11.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 11/09/2018] [Accepted: 11/12/2018] [Indexed: 02/07/2023]
Abstract
The periosteum and mineralized bone are innervated by nerves that sense pain. These include both myelinated and unmyelinated neurons with either free nerve endings or bearing nociceptors. Parasympathetic and sympathetic autonomic nerves also innervate bone. However, little is known about the route sensory nerves take leaving the epiphyses of long bones at the adult knee joint. Here, we used transgenic mice that express fluorescent Venus protein in Schwann cells (Sox10-Venus mice) to visualize myelinated and unmyelinated nerves in the tibial epiphysis. Immunofluorescence to detect a pan-neuronal marker and the sensory neuron markers calcitonin gene-related peptide (CGRP) and tropomyosin receptor kinase A (TrkA) also revealed Schwann cell-associated sensory neurons. Foramina in the intercondylar area of the tibia were conserved between rodents and primates. Venus-labeled fibers were detected within bone marrow of the proximal epiphysis, exited through foramina along with blood vessels in the intercondylar area of the tibia, and joined Venus-labeled fibers of the synovial membrane and meniscus. These data suggest that innervation of the subchondral plate and trabecular bone within the tibial epiphysis carries pain signals from the knee joint to the brain through intercondylar foramina.
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Affiliation(s)
- Koichi Matsuo
- Laboratory of Cell and Tissue Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
| | - Shuting Ji
- Laboratory of Cell and Tissue Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Ayako Miya
- Laboratory of Cell and Tissue Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Masaki Yoda
- Laboratory of Cell and Tissue Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Yuzuru Hamada
- Morphology Section, Primate Research Institute, Kyoto University, 41 Kanrin, Inuyama 484-8506, Japan
| | - Tomoya Tanaka
- Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1 Mifuku, Izunokuni, Shizuoka 410-2321, Japan
| | - Ryoko Takao-Kawabata
- Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1 Mifuku, Izunokuni, Shizuoka 410-2321, Japan
| | - Katsuhiro Kawaai
- Laboratory of Cell and Tissue Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Yukiko Kuroda
- Laboratory of Cell and Tissue Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Shinsuke Shibata
- Electron Microscope Laboratory, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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Pazzaglia UE, Sibilia V, Casati L, Salvi AG, Minini A, Reguzzoni M. The missing segment of the autopod 1st ray: new insights from a morphometric study of the human hand. J Anat 2018; 233:828-842. [PMID: 30368800 PMCID: PMC6231165 DOI: 10.1111/joa.12883] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/2018] [Indexed: 12/16/2022] Open
Abstract
Whether the 1st segment of the human autopod 1st ray is a 'true' metapodial with loss of the proximal or mid phalanx or the original basal phalanx with loss of the metacarpal has been a long-lasting discussion. The actual knowledge of the developmental pattern of upper autopod segments at a fetal age of 20-22 weeks, combined with X-ray morphometry of normal long bones of the hand in the growing ages, was used for analysis of the parameters, percentage length, position of epiphyseal ossification centers and proximal/distal growth rate. The symmetric growth pattern in the fetal anlagen changed to unidirectional in the postnatal development in relation to epiphyseal ossification formation. The percentage length assessment, the distribution of the epiphyseal ossification centers, and differential proximal/distal growth rate among the growing hand segments supported homology of most proximal segment of the thumb with the 2nd-5th proximal phalanges and that of the proximal phalanx of the thumb with the 2nd-5th mid phalanges in the same hand. Published case reports of either metanalysis of 'triphalangeal thumb' and 'proximal/distal epiphyseal ossification centers' were used to support the applied morphometric methodology; in particular, the latter did not give evidence of growth pattern inversion of the proximal segment of the thumb. The presented data support the hypothesis that during evolution, the lost segment of the autopod 1st ray is the metacarpal.
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Affiliation(s)
- Ugo E. Pazzaglia
- Department of Medical and Surgical SpecialtiesRadiological Sciences and Public HealthUniversity of BresciaBresciaItaly
| | - Valeria Sibilia
- Department of Medical Biotechnology and Translational MedicineUniversity of MilanMilanoItaly
| | - Lavinia Casati
- Department of Medical Biotechnology and Translational MedicineUniversity of MilanMilanoItaly
| | - Andrea G. Salvi
- Department of Medical and Surgical SpecialtiesRadiological Sciences and Public HealthUniversity of BresciaBresciaItaly
| | - Andrea Minini
- Department of Medical and Surgical SpecialtiesRadiological Sciences and Public HealthUniversity of BresciaBresciaItaly
| | - Marcella Reguzzoni
- Department of Surgical and Morphological SciencesUniversity of InsubriaVareseItaly
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Richtsmeier JT. A century of development. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2018; 165:726-740. [PMID: 29574839 PMCID: PMC6007869 DOI: 10.1002/ajpa.23379] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 12/02/2017] [Accepted: 12/09/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Joan T Richtsmeier
- Department of Anthropology, Pennsylvania State University, University Park, Pennsylvania 16802
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Gregorovičová M, Kvasilová A, Sedmera D. Ossification Pattern in Forelimbs of the Siamese Crocodile (
Crocodylus siamensis
): Similarity in Ontogeny of Carpus Among Crocodylian Species. Anat Rec (Hoboken) 2018; 301:1159-1168. [DOI: 10.1002/ar.23792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 09/16/2017] [Accepted: 10/04/2017] [Indexed: 01/31/2023]
Affiliation(s)
- Martina Gregorovičová
- Institute of Physiology, Department of Developmental Cardiology, The Czech Academy of SciencesVídeňská 1083, Praha 4, 142 20 Czech Republic
- Institute of Anatomy, First Faculty of MedicineCharles UniversityU nemocnice 3, Praha 2, 128 00 Czech Republic
| | - Alena Kvasilová
- Institute of Anatomy, First Faculty of MedicineCharles UniversityU nemocnice 3, Praha 2, 128 00 Czech Republic
| | - David Sedmera
- Institute of Physiology, Department of Developmental Cardiology, The Czech Academy of SciencesVídeňská 1083, Praha 4, 142 20 Czech Republic
- Institute of Anatomy, First Faculty of MedicineCharles UniversityU nemocnice 3, Praha 2, 128 00 Czech Republic
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Pazzaglia UE, Congiu T, Sibilia V, Casati L, Minini A, Benetti A. Growth and shaping of metacarpal and carpal cartilage anlagen: application of morphometry to the development of short and long bone. A study of human hand anlagen in the fetal period. J Morphol 2017; 278:884-895. [DOI: 10.1002/jmor.20681] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/08/2017] [Accepted: 03/19/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Ugo E. Pazzaglia
- Department of Medical and Surgical Specialties; Radiological Sciences and Public Health, University of Brescia; Italy
| | - Terenzio Congiu
- Department of Surgical and Morphological Sciences; University of Insubria; Varese Italy
| | - Valeria Sibilia
- Department of Medical Biotechnology and Translational Medicine; University of Milan; Italy
| | - Lavinia Casati
- Department of Medical Biotechnology and Translational Medicine; University of Milan; Italy
| | - Andrea Minini
- Department of Medical and Surgical Specialties; Radiological Sciences and Public Health, University of Brescia; Italy
| | - Anna Benetti
- Department of Clinical and Experimental Sciences; University of Brescia; Italy
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Reno PL, Kjosness KM, Hines JE. The Role of Hox in Pisiform and Calcaneus Growth Plate Formation and the Nature of the Zeugopod/Autopod Boundary. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2016; 326:303-21. [DOI: 10.1002/jez.b.22688] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 06/13/2016] [Accepted: 06/28/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Philip L. Reno
- Department of Anthropology; The Pennsylvania State University; University Park Pennsylvania
| | - Kelsey M. Kjosness
- Department of Anthropology; The Pennsylvania State University; University Park Pennsylvania
| | - Jasmine E. Hines
- Department of Anthropology; The Pennsylvania State University; University Park Pennsylvania
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Botelho JF, Smith-Paredes D, Soto-Acuña S, O'Connor J, Palma V, Vargas AO. Molecular development of fibular reduction in birds and its evolution from dinosaurs. Evolution 2016; 70:543-54. [PMID: 26888088 PMCID: PMC5069580 DOI: 10.1111/evo.12882] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Revised: 01/02/2016] [Accepted: 01/27/2016] [Indexed: 01/05/2023]
Abstract
Birds have a distally reduced, splinter‐like fibula that is shorter than the tibia. In embryonic development, both skeletal elements start out with similar lengths. We examined molecular markers of cartilage differentiation in chicken embryos. We found that the distal end of the fibula expresses Indian hedgehog (IHH), undergoing terminal cartilage differentiation, and almost no Parathyroid‐related protein (PTHrP), which is required to develop a proliferative growth plate (epiphysis). Reduction of the distal fibula may be influenced earlier by its close contact with the nearby fibulare, which strongly expresses PTHrP. The epiphysis‐like fibulare however then separates from the fibula, which fails to maintain a distal growth plate, and fibular reduction ensues. Experimental downregulation of IHH signaling at a postmorphogenetic stage led to a tibia and fibula of equal length: The fibula is longer than in controls and fused to the fibulare, whereas the tibia is shorter and bent. We propose that the presence of a distal fibular epiphysis may constrain greater growth in the tibia. Accordingly, many Mesozoic birds show a fibula that has lost its distal epiphysis, but remains almost as long as the tibia, suggesting that loss of the fibulare preceded and allowed subsequent evolution of great fibulo–tibial disparity.
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Affiliation(s)
- João Francisco Botelho
- Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias de la Universidad de Chile, Santiago, Chile.
| | - Daniel Smith-Paredes
- Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias de la Universidad de Chile, Santiago, Chile
| | - Sergio Soto-Acuña
- Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias de la Universidad de Chile, Santiago, Chile.,Área de Paleontología, Museo Nacional de Historia Natural, Santiago, Chile
| | - Jingmai O'Connor
- Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Science, Beijing, China
| | - Verónica Palma
- FONDAP Center for Genomic Regulation, Departamento de Biología, Facultad de Ciencias de la Universidad de Chile, Santiago, Chile
| | - Alexander O Vargas
- Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias de la Universidad de Chile, Santiago, Chile.
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Kjosness KM, Hines JE, Lovejoy CO, Reno PL. The pisiform growth plate is lost in humans and supports a role for Hox in growth plate formation. J Anat 2014; 225:527-38. [PMID: 25279687 PMCID: PMC4292754 DOI: 10.1111/joa.12235] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/20/2014] [Indexed: 12/29/2022] Open
Abstract
The human pisiform is a small, nodular, although functionally significant, bone of the wrist. In most other mammals, including apes and Australopithecus afarensis, pisiforms are elongate. An underappreciated fact is that the typical mammalian pisiform forms from two ossification centers. We hypothesize that: (i) the presence of a secondary ossification center in mammalian pisiforms indicates the existence of a growth plate; and (ii) human pisiform reduction results from growth plate loss. To address these hypotheses, we surveyed African ape pisiform ossification and confirmed the presence of a late-forming secondary ossification center in chimpanzees and gorillas. Identification of the initial ossification center occurs substantially earlier in apes relative to humans, raising questions concerning the homology of the human pisiform and the two mammalian ossification centers. Second, we conducted histological and immunohistochemical analyses of pisiform ossification in mice. We confirm the presence of two ossification centers separated by organized columnar and hypertrophic chondrocyte zones. Flattened chondrocytes were highly mitotic, indicating the presence of a growth plate. Hox genes have been proposed to play a fundamental role in growth plate patterning. The existence of a pisiform growth plate presents an interesting test case for the association between Hox expression and growth plate formation, and could explain the severe effects on the pisiform observed in Hoxa11 and Hoxd11 knockout mice. Consistent with this hypothesis, we show that Hoxd11 is expressed adjacent to the pisiform in late-stage embryonic mouse limbs supporting a role for Hox genes in growth plate specification. This raises questions concerning the mechanisms regulating Hox expression in the developing carpus.
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Affiliation(s)
- Kelsey M Kjosness
- Department of Anthropology, The Pennsylvania State University, University Park, PA, USA
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Reno PL, Horton WE, Lovejoy CO. Metapodial or phalanx? An evolutionary and developmental perspective on the homology of the first ray's proximal segment. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 320:276-85. [PMID: 23640850 DOI: 10.1002/jez.b.22506] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 03/29/2013] [Accepted: 04/01/2013] [Indexed: 12/30/2022]
Abstract
The first mammalian metapodial (MP1) has periodically been argued to actually be a phalanx, because the first ray has one less element than the four posterior rays, and because the MP1 growth plate is proximal like those of all phalanges, rather than distal as in metapodials 2-5. However, growth plates are formed at both ends in non-therian tetrapod metapodials, and phylogenetic analysis demonstrates that growth plate loss is a therian synapomorphy that postdates the establishment of the mammalian phalangeal formula. These data, along with results of developmental and morphological studies, suggest that the MP1 is not a phalanx. The singular, proximal growth plates in MPs 2-5 are likely to be an adaptation to dynamic erect quadrupedal gait which was characterized by conversion of the posterior metapodials into rigid struts with the carpus/tarsus. While the adaptive significance of the reversed ossification of MP1 is less clear, we present three functional/developmental hypotheses.
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Affiliation(s)
- Philip L Reno
- Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania, USA.
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Lovejoy CO, Latimer B, Suwa G, Asfaw B, White TD. Combining Prehension and Propulsion: The Foot of Ardipithecus ramidus. Science 2009. [DOI: 10.1126/science.1175832] [Citation(s) in RCA: 170] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Chen X, Macica CM, Nasiri A, Broadus AE. Regulation of articular chondrocyte proliferation and differentiation by indian hedgehog and parathyroid hormone-related protein in mice. ACTA ACUST UNITED AC 2009; 58:3788-97. [PMID: 19035497 DOI: 10.1002/art.23985] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Chondrocytes of the epiphyseal growth zone are regulated by the Indian hedgehog (IHH)-parathyroid hormone-related protein (PTHrP) axis. In weight-bearing joints, this growth zone comes to be subdivided by the secondary ossification center into distinct articular and growth cartilage structures. The purpose of this study was to explore the cells of origin, localization, regulation of expression, and putative functions of IHH and PTHrP in articular cartilage in the mouse. METHODS We assessed IHH and PTHrP expression in an allelic PTHrP-LacZ-knockin mouse and several versions of PTHrP-null mice. Selected joints were unloaded surgically to examine load-induction of PTHrP and IHH. RESULTS The embryonic growth zone appears to serve as the source of PTHrP-expressing proliferative chondrocytes that populate both the forming articular cartilage and growth plate structures. In articular cartilage, these cells take the form of articular chondrocytes in the midzone. In PTHrP-knockout mice, mineralizing chondrocytes encroach upon developing articular cartilage but appear to be prevented from mineralizing the joint space by IHH-driven surface chondrocyte proliferation. In growing and adult mice, PTHrP expression in articular chondrocytes is load-induced, and unloading is associated with rapid changes in PTHrP expression and articular chondrocyte differentiation. CONCLUSION We conclude that the IHH-PTHrP axis participates in the maintenance of articular cartilage. Dysregulation of this system might contribute to the pathogenesis of arthritis.
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Affiliation(s)
- Xuesong Chen
- Yale University School of Medicine, New Haven, Connecticut 06520-8020, USA
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Jerez A, Tarazona OA. Appendicular skeleton inBachia bicolor(Squamata: Gymnophthalmidae): osteology, limb reduction and postnatal skeletal ontogeny. ACTA ZOOL-STOCKHOLM 2009. [DOI: 10.1111/j.1463-6395.2008.00331.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Reno PL, McCollum MA, Cohn MJ, Meindl RS, Hamrick M, Lovejoy CO. Patterns of correlation and covariation of anthropoid distal forelimb segments correspond to Hoxd expression territories. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:240-58. [DOI: 10.1002/jez.b.21207] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Abstract
A network of interactions is called modular if it is subdivided into relatively autonomous, internally highly connected components. Modularity has emerged as a rallying point for research in developmental and evolutionary biology (and specifically evo-devo), as well as in molecular systems biology. Here we review the evidence for modularity and models about its origin. Although there is an emerging agreement that organisms have a modular organization, the main open problem is the question of whether modules arise through the action of natural selection or because of biased mutational mechanisms.
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