Publications
105 results found
Abzhanov A, 2018, Morphogenetic mechanisms for evolvability in avian adaptive radiations, First European Regional Meeting on Vertebrate Morphology, Society for Integrative & Comparative Biology
Abzhanov A, 2017, The old and new faces of morphology: the legacy of D'Arcy Thompson's 'theory of transformations' and 'laws of growth', Development, Vol: 144, Pages: 4284-4297, ISSN: 0950-1991
In 1917, the publication of On Growth and Form by D'Arcy Wentworth Thompson challenged both mathematicians and naturalists to think about biological shapes and diversity as more than a confusion of chaotic forms generated at random, but rather as geometric shapes that could be described by principles of physics and mathematics. Thompson's work was based on the ideas of Galileo and Goethe on morphology and of Russell on functionalism, but he was first to postulate that physical forces and internal growth parameters regulate biological forms and could be revealed via geometric transformations in morphological space. Such precise mathematical structure suggested a unifying generative process, as reflected in the title of the book. To Thompson it was growth that could explain the generation of any particular biological form, and changes in ontogeny, rather than natural selection, could then explain the diversity of biological shapes. Whereas adaptationism, widely accepted in evolutionary biology, gives primacy to extrinsic factors in producing morphological variation, Thompson's ‘laws of growth' provide intrinsic directives and constraints for the generation of individual shapes, helping to explain the ‘profusion of forms, colours, and other modifications' observed in the living world.
Fabbri M, Koch NM, Pritchard AC, et al., 2017, The skull roof tracks the brain during the evolution and development of reptiles including birds, Nature Ecology and Evolution, Vol: 1, Pages: 1543-1550, ISSN: 2397-334X
Major transformations in brain size and proportions, such as the enlargement of the brain during the evolution of birds, are accompanied by profound modifications to the skull roof. However, the hypothesis of concerted evolution of shape between brain and skull roof over major phylogenetic transitions, and in particular of an ontogenetic relationship between specific regions of the brain and the skull roof, has never been formally tested. We performed 3D morphometric analyses to examine the deep history of brain and skull-roof morphology in Reptilia, focusing on changes during the well-documented transition from early reptiles through archosauromorphs, including nonavian dinosaurs, to birds. Non-avialan taxa cluster tightly together in morphospace, whereas Archaeopteryx and crown birds occupy a separate region. There is a one-to-one correspondence between the forebrain and frontal bone and the midbrain and parietal bone. Furthermore, the position of the forebrain–midbrain boundary correlates significantly with the position of the frontoparietal suture across the phylogenetic breadth of Reptilia and during the ontogeny of individual taxa. Conservation of position and identity in the skull roof is apparent, and there is no support for previous hypotheses that the avian parietal is a transformed postparietal. The correlation and apparent developmental link between regions of the brain and bony skull elements are likely to be ancestral to Tetrapoda and may be fundamental to all of Osteichthyes, coeval with the origin of the dermatocranium.
Abzhanov A, 2017, Phylogenetic principles and morphogenetic mechanisms for evolvability in avian adaptive radiations, EMBO conference
Abzhanov A, 2017, Phylogenetic evidence and ontogenetic mechanisms for evolvability in avian adaptive radiations, Joint Congress 2017
Abzhanov A, 2017, Developmental evolution of the animal face: insights into the origins of adaptive radiations, UK Evo-Devo Conference
Morris ZS, Pierce SE, Abzhanov A, 2017, Craniofacial growth zones and modularity in Amniota: insight from the model crocodylian, Alligator mississippiensis., Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E355-E355, ISSN: 1540-7063
Abzhanov A, 2017, Evolution of the Animal Face: from Principles to Mechanisms, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E189-E189, ISSN: 1540-7063
Tokita M, Yano W, James HF, et al., 2016, Cranial shape evolution in adaptive radiations of birds: comparative morphometrics of Darwin's finches and Hawaiian honeycreepers, Philosophical Transactions B: Biological Sciences, Vol: 372, ISSN: 0962-8436
Adaptive radiation is the rapid evolution of morphologically and ecologically diverse species from a single ancestor. The two classic examples of adaptive radiation are Darwin's finches and the Hawaiian honeycreepers, which evolved remarkable levels of adaptive cranial morphological variation. To gain new insights into the nature of their diversification, we performed comparative three-dimensional geometric morphometric analyses based on X-ray microcomputed tomography (µCT) scanning of dried cranial skeletons. We show that cranial shapes in both Hawaiian honeycreepers and Coerebinae (Darwin's finches and their close relatives) are much more diverse than in their respective outgroups, but Hawaiian honeycreepers as a group display the highest diversity and disparity of all other bird groups studied. We also report a significant contribution of allometry to skull shape variation, and distinct patterns of evolutionary change in skull morphology in the two lineages of songbirds that underwent adaptive radiation on oceanic islands. These findings help to better understand the nature of adaptive radiations in general and provide a foundation for future investigations on the developmental and molecular mechanisms underlying diversification of these morphologically distinguished groups of birds.This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.
Abzhanov A, 2016, Developmental Integration and Evolution of the Avian Face, BMP Conference
Abzhanov A, 2016, Evolution of the Animal Face: from Principles to Mechanisms, Anatomical Society 2017 Conference
Abzhanov A, 2016, Evolution of the Animal Face: from Principles to Mechanisms, Anatomical Society 2017 Conference
Abzhanov A, 2016, Developmental evolution of the animal face: insights into the origins of adaptive radiations, Society for Comparative and Integrative Biology
Camacho J, Heyde A, Bhullar BAS, et al., 2016, The evolution and development of diverse and adaptive skull shapes in New World leaf-nosed bats, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E30-E30, ISSN: 1540-7063
Abzhanov A, 2016, Developmental evolution of the animal face: insights into the origins of adaptive radiations, Euro Evo-Devo Conference
Namkoong B, Guven S, Ramesan S, et al., 2015, Recapitulating cranial osteogenesis with neural crest cells in 3-D microenvironments, Acta Biomaterialia, Vol: 31, Pages: 301-311, ISSN: 1878-7568
The experimental systems that recapitulate the complexity of native tissues and enable precise control over the microenvironment are becoming essential for the pre-clinical tests of therapeutics and tissue engineering. Here, we described a strategy to develop an in vitro platform to study the developmental biology of craniofacial osteogenesis. In this study, we directly osteo-differentiated cranial neural crest cells (CNCCs) in a 3-D in vitro bioengineered microenvironment. Cells were encapsulated in the gelatin-based photo-crosslinkable hydrogel and cultured up to three weeks. We demonstrated that this platform allows efficient differentiation of p75 positive CNCCs to cells expressing osteogenic markers corresponding to the sequential developmental phases of intramembranous ossification. During the course of culture, we observed a decrease in the expression of early osteogenic marker Runx2, while the other mature osteoblast and osteocyte markers such as Osterix, Osteocalcin, Osteopontin and Bone sialoprotein increased. We analyzed the ossification of the secreted matrix with alkaline phosphatase and quantified the newly secreted hydroxyapatite. The Field Emission Scanning Electron Microscope (FESEM) images of the bioengineered hydrogel constructs revealed the native-like osteocytes, mature osteoblasts, and cranial bone tissue morphologies with canaliculus-like intercellular connections. This platform provides a broadly applicable model system to potentially study diseases involving primarily embryonic craniofacial bone disorders, where direct diagnosis and adequate animal disease models are limited.
Abzhanov A, 2015, Evolution of the Animal Face: from Principles to Mechanisms, Triangle Developmental Biology Symposium
Abzhanov A, 2015, Developmental Integration and Evolution of the Avian Face, Keystone Symposia Conference “Molecular and Cellular Basis of Growth and Regeneration” i
Namkong B, Guven S, Ramesan S, et al., 2015, Recapitulating Cranial Osteogenesis with Neural Crest Cells in 3-d Microenvironments, 4th TERMIS World Congress, Publisher: MARY ANN LIEBERT, INC, Pages: S337-S337, ISSN: 1937-3341
Bhullar B-AS, Morris ZS, Sefton EM, et al., 2015, A molecular mechanism for the origin of a key evolutionary innovation, the bird beak and palate, revealed by an integrative approach to major transitions in vertebrate history, Evolution, Vol: 69, Pages: 1665-1677, ISSN: 0014-3820
The avian beak is a key evolutionary innovation whose flexibility has permitted birds to diversify into a range of disparate ecological niches. We approached the problem of the mechanism behind this innovation using an approach bridging paleontology, comparative anatomy, and experimental developmental biology. First, we used fossil and extant data to show the beak is distinctive in consisting of fused premaxillae that are geometrically distinct from those of ancestral archosaurs. To elucidate underlying developmental mechanisms, we examined candidate gene expression domains in the embryonic face: the earlier frontonasal ectodermal zone (FEZ) and the later midfacial WNTâresponsive region, in birds and several reptiles. This permitted the identification of an autapomorphic median gene expression region in Aves. To test the mechanism, we used inhibitors of both pathways to replicate in chicken the ancestral amniote expression. Altering the FEZ altered later WNT responsiveness to the ancestral pattern. Skeletal phenotypes from both types of experiments had premaxillae that clustered geometrically with ancestral fossil forms instead of beaked birds. The palatal region was also altered to a more ancestral phenotype. This is consistent with the fossil record and with the tight functional association of avian premaxillae and palate in forming a kinetic beak.
Abzhanov A, 2015, Evolution of the Animal Face: from Principles to Mechanisms, Experimental Biology Meeting, Publisher: FEDERATION AMER SOC EXP BIOL, ISSN: 0892-6638
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- Citations: 1
Sanger TJ, Seav SM, Tokita M, et al., 2014, The oestrogen pathway underlies the evolution of exaggerated male cranial shapes in <i>Anolis lizards</i>, PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 281, ISSN: 0962-8452
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- Citations: 26
Fritz JA, Brancale J, Tokita M, et al., 2014, Shared developmental programme strongly constrains beak shape diversity in songbirds, NATURE COMMUNICATIONS, Vol: 5, ISSN: 2041-1723
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- Citations: 38
Abzhanov A, 2013, von Baer's law for the ages: lost and found principles of developmental evolution, TRENDS IN GENETICS, Vol: 29, Pages: 712-722, ISSN: 0168-9525
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- Citations: 51
Weeks O, Bhullar B-AS, Abzhanov A, 2013, Molecular characterization of dental development in a toothed archosaur, the American alligator <i>Alligator mississippiensis</i>, EVOLUTION & DEVELOPMENT, Vol: 15, Pages: 393-405, ISSN: 1520-541X
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- Citations: 13
Lyson TR, Bhullar B-AS, Bever GS, et al., 2013, Homology of the enigmatic nuchal bone reveals novel reorganization of the shoulder girdle in the evolution of the turtle shell, EVOLUTION & DEVELOPMENT, Vol: 15, Pages: 317-325, ISSN: 1520-541X
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- Citations: 44
Sanger TJ, Sherratt E, McGlothlin JW, et al., 2013, CONVERGENT EVOLUTION OF SEXUAL DIMORPHISM IN SKULL SHAPE USING DISTINCT DEVELOPMENTAL STRATEGIES, EVOLUTION, Vol: 67, Pages: 2180-2193, ISSN: 0014-3820
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- Citations: 66
Abzhanov A, 2013, Developmental mechanisms for morphological evolution, Joint Annual Meeting of the ASPET/BPS at Experimental Biology (EB), Publisher: FEDERATION AMER SOC EXP BIOL, ISSN: 0892-6638
Bhullar B-AS, Marugan-Lobon J, Racimo F, et al., 2013, The evolution and development of the archosaurian head and the origin of the bird skull, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E16-E16, ISSN: 1540-7063
Rands CM, Darling A, Fujita M, et al., 2013, Insights into the evolution of Darwin’s finches from comparative analysis of the Geospiza magnirostris genome sequence, BMC Genomics, Vol: 14, ISSN: 1471-2164
BACKGROUND: A classical example of repeated speciation coupled with ecological diversification is the evolution of 14 closely related species of Darwin's (Galápagos) finches (Thraupidae, Passeriformes). Their adaptive radiation in the Galápagos archipelago took place in the last 2-3 million years and some of the molecular mechanisms that led to their diversification are now being elucidated. Here we report evolutionary analyses of genome of the large ground finch, Geospiza magnirostris. RESULTS: 13,291 protein-coding genes were predicted from a 991.0 Mb G. magnirostris genome assembly. We then defined gene orthology relationships and constructed whole genome alignments between the G. magnirostris and other vertebrate genomes. We estimate that 15% of genomic sequence is functionally constrained between G. magnirostris and zebra finch. Genic evolutionary rate comparisons indicate that similar selective pressures acted along the G. magnirostris and zebra finch lineages suggesting that historical effective population size values have been similar in both lineages. 21 otherwise highly conserved genes were identified that each show evidence for positive selection on amino acid changes in the Darwin's finch lineage. Two of these genes (Igf2r and Pou1f1) have been implicated in beak morphology changes in Darwin's finches. Five of 47 genes showing evidence of positive selection in early passerine evolution have cilia related functions, and may be examples of adaptively evolving reproductive proteins. CONCLUSIONS: These results provide insights into past evolutionary processes that have shaped G. magnirostris genes and its genome, and provide the necessary foundation upon which to build population genomics resources that will shed light on more contemporaneous adaptive and non-adaptive processes that have contributed to the evolution of the Darwin's finches.
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