title: Mammary glands and feathers: comparing two skin appendages which help define novel classes during vertebrate evolution.
abstract: It may appear counter-intuitive to compare feathers and mammary glands. However, through this Evo-Devo analysis, we appreciate how species interact with the environment, requiring different ectodermal organs. Novel ectodermal organs help define evolutionary directions, leading to new organism classes as exemplified by feathers for Aves and mammary glands for Mammals. Here, we review their structure, function, morphogenesis and regenerative cycling. Interestingly, both organs undergo extensive branching for different reasons; feather branching is driven by mechanical advantage while mammary glands nourish young. Besides natural selection, both are regulated by sex hormones and acquired a secondary function for attracting mates, contributing to sexual selection.
authors: Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. widelitz@usc.edu
authors: Randall B
authors: RB
authors: Widelitz
authors: Jacqueline M
authors: JM
authors: Veltmaat
authors: Julie Ann
authors: JA
authors: Mayer
authors: John
authors: J
authors: Foley
authors: Cheng-Ming
authors: CM
authors: Chuong
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005241:Feathers / Q000196:embryology*; D006801:Humans; D034582:Integumentary System / Q000196:embryology*; D042361:Mammary Glands, Human / Q000196:embryology*; D008954:Models, Biological; D014714:Vertebrates / Q000196:embryology*