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Front Cell Dev Biol. 2017 Mar 23;5:23. doi: 10.3389/fcell.2017.00023. eCollection 2017.

Sox9 Expression in Amniotes: Species-Specific Differences in the Formation of Digits.

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Departamento de Anatomía y Biología Celular and IDIVAL, Universidad de Cantabria Santander, Spain.
Departamento de Anatomía, Biología Celular, y Zoología, Universidad de Extremadura Badajoz, Spain.
Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Mexico City, Mexico.


In tetrapods the digit pattern has evolved to adapt to distinct locomotive strategies. The number of digits varies between species or even between hindlimb and forelimb within the same species. These facts illustrate the plasticity of embryonic limb autopods. Sox9 is a precocious marker of skeletal differentiation of limb mesenchymal cells. Its pattern of expression in the developing limb has been widely studied and reflects the activity of signaling cascades responsible for skeletogenesis. In this assay we stress previously overlooked differences in the pattern of expression of Sox9 in limbs of avian, mouse and turtle embryos which may reflect signaling differences associated with distinct limb skeletal morphologies observed in these species. Furthermore, we show that Sox9 gene expression is higher and maintained in the interdigital region in species with webbed digits in comparison with free digit animals.


SOX9 transcription factor; chondrogenesis; interdigit regression; limb development; skeletal progenitors

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