Cadherins are a group of membrane proteins responsible for cell adhesion. They are crucial for cell sorting and recognition during the morphogenesis, but they also play many other roles such as assuring tissue integrity and resistance to stretching, mechanotransduction, cell signaling, regulation of cell proliferation, apoptosis, survival, carcinogenesis, etc. Within the cadherin superfamily, E- and N-cadherin have been especially well studied. They are involved in many aspects of sexual development and reproduction, such as germline development and gametogenesis, gonad development and functioning, and fertilization. E-cadherin is expressed in the primordial germ cells (PGCs) and also participates in PGC migration to the developing gonads where they become enclosed by the N-cadherin-expressing somatic cells. The differential expression of cadherins is also responsible for the establishment of the testis or ovary structure. In the adult testes, N-cadherin is responsible for the integrity of the seminiferous epithelium, regulation of sperm production, and the establishment of the blood–testis barrier. Sex hormones regulate the expression and turnover of N-cadherin influencing the course of spermatogenesis. In the adult ovaries, E- and N-cadherin assure the integrity of ovarian follicles and the formation of corpora lutea. Cadherins are expressed in the mature gametes and facilitate the capacitation of sperm in the female reproductive tract and gamete contact during fertilization. The germ cells and accompanying somatic cells express a series of different cadherins; however, their role in gonads and reproduction is still unknown. In this review, we show what is known and unknown about the role of cadherins in the germline and gonad development, and we suggest topics for future research.

Cadherins are a group of membrane proteins responsible for cell adhesion. They are crucial for cell sorting and recognition during the morphogenesis, but also play many other roles such as assuring tissue integrity and resistance to stretching, mechanotransduction, cell signaling, regulation of cell proliferation, apoptosis, survival, carcinogenesis, etc. Within the cadherin superfamily, the E- and N-cadherin have been especially well studied. They are involved in many aspects of sexual development and reproduction, such as germline development and gametogenesis, gonad development and functioning, and fertilization. E-cadherin is expressed in the primordial germ cells, (PGCs) and also participates in PGC migration to the developing gonads where they become enclosed by the N-cadherin-expressing somatic cells. The differential expression of cadherins is also responsible for the establishment of the testis or ovary structure. In the adult testes, the N-cadherin is responsible for the integrity of the seminiferous epithelium, regulation of sperm production, and the establishment of the blood-testis barrier. Sex hormones regulate the expression and turnover of N-cadherin influencing the course of spermatogenesis. In the adult ovaries, E- and N-cadherin assure the integrity of ovarian follicles and the formation of corpora lutea. Cadherins are expressed in the mature gametes, and facilitate the capacitation of sperm in the female reproductive tract, and gamete contact during fertilization. The germ cells and accompanying somatic cells express a series of different cadherins, however, their role in gonads and reproduction is still unknown. In this review, we show what is known and unknown about the role of cadherins in the germline and gonad development, and suggest the topics for future research.

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W skórze przedstawicieli kilku grup czworonogów występują skostnienia zwane osteodermami. Osteodermy były już obecne w skórze pierwszych czworonogów, które pojawiły się w dewonie. Podczas ewolucji osteodermy uległy zanikowi w wielu liniach ewolucyjnych. Utraciły je węże, amfisbeny, pterozaury i ptaki oraz większość płazów i ssaków. Pojawiły się także de novo co najmniej pięć razy wśród owodniowców. Osteodermy obecne są u sześciu rodzin płazów bezogonowych, gdzie występują głównie na grzbietowej stronie ciała. Wspierają również skórę krokodyli i jaszczurek. Były wysoko rozwinięte, również u ankylozaurów i stegozaurów, czyli w dwóch liniach dinozaurów. Wchodzą w skład pancerza żółwi i wymarłych plakodontów. Wśród synapsydów osteodermy występowały u dwóch permskich gatunków, a wśród ssaków tylko u pancerników oraz wymarłych leniwców naziemnych i gliptodontów. Biorąc pod uwagę zmineralizowane struktury skóry, należy również wspomnieć o blaszce wapiennej u płazów bezogonowych oraz o łuskach skórnych u płazów beznogich. Jednak struktury te nie są tkanką kostną i dlatego nie są klasyfikowane jako osteodermy. Analiza porównawcza ujawnia, że ​​osteodermy są plezjomorficzną cechą czworonogów, a więc odziedziczoną po rybich przodkach, a ich utrata i ponowne pojawianie się w ewolucji sprawia, że ​​osteodermy są wartościowym przedmiotem badań nad ewolucyjną plastycznością.

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