The anatomical placode in reptile scale morphogenesis indicates shared ancestry among skin appendages in amniotes

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Di Poi , N & Milinkovitch , M 2016 , ' The anatomical placode in reptile scale morphogenesis indicates shared ancestry among skin appendages in amniotes ' , Science Advances , vol. 2 , no. 6 , e1600708 . https://doi.org/10.1126/sciadv.1600708

Title: The anatomical placode in reptile scale morphogenesis indicates shared ancestry among skin appendages in amniotes
Author: Di Poi, Nicholas; Milinkovitch, Michel
Contributor: University of Helsinki, Institute of Biotechnology
Date: 2016-06-24
Language: eng
Number of pages: 9
Belongs to series: Science Advances
ISSN: 2375-2548
URI: http://hdl.handle.net/10138/165876
Abstract: Most mammals, birds, and reptiles are readily recognized by their hairs, feathers, and scales, respectively. However, the lack of fossil intermediate forms between scales and hairs and substantial differences in their morphogenesis and protein composition have fueled the controversy pertaining to their potential common ancestry for decades. Central to this debate is the apparent lack of an “anatomical placode” (that is, a local epidermal thickening characteristic of feathers’ and hairs’ early morphogenesis) in reptile scale development. Hence, scenarios have been proposed for the independent development of the anatomical placode in birds and mammals and parallel co-option of similar signaling pathways for their morphogenesis. Using histological and molecular techniques on developmental series of crocodiles and snakes, as well as of unique wild-type and EDA (ectodysplasin A)–deficient scaleless mutant lizards, we show for the first time that reptiles, including crocodiles and squamates, develop all the characteristics of an anatomical placode: columnar cells with reduced proliferation rate, as well as canonical spatial expression of placode and underlying dermal molecular markers. These results reveal a new evolutionary scenario where hairs, feathers, and scales of extant species are homologous structures inherited, with modification, from their shared reptilian ancestor’s skin appendages already characterized by an anatomical placode and associated signaling molecules.
Subject: 1181 Ecology, evolutionary biology
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