Desmoplakin (Dsp) conditional knockout in NR5A1+ somatic cells affects germ cell survival in developing mouse gonads.

Cell to cell interactions are crucial for morphogenesis and tissue formation. Desmoplakin (encoded by the Dsp gene) is a component of desmosomes and anchors the transmembrane adhesion proteins to the cytoskeleton. Its role in gonad development remains vague. To study the role of desmoplakin in gonad development, we used a tissue-specific knockout of the Dsp gene in the NR5A1+ somatic cells of the gonads. We show here that desmoplakin is necessary for the survival of germ cells in fetal testes and ovaries. The Dspknockout in NR5A1+ somatic cells in testes decreased the number of germ cells, and thus the size of the testes, but did not affect the Sertoli cells or the structure of testis cords and interstitium. The Dspknockout in NR5A1+ somatic cells in ovaries decreased the number of female germ cells and drastically reduced the formation of ovarian follicles. Dsp knockout in NR5A1+ somatic cells did not affect the sex determination and sexual differentiation of the gonads, as judged from an unchanged expression of genes essential for these processes. We conclude that mediation by desmoplakin cell adhesion between the gonadal cells is necessary for germ cell survival.

Histological Analysis of Gonadal Ridge Development and Sex Differentiation of Gonads in Three Gecko Species.

Reptiles constitute a highly diverse group of vertebrates, with their evolutionary lineages having diverged relatively early. The types of sex determination exemplify the diversity of reptiles; however, there are limited data regarding the gonadal development in squamate reptiles. Geckos constitute a group that is increasingly used in research and that serves as a potential reptilian model organism. The aim of this study was to trace the changes in the structure of developing gonads in the embryos of three gecko species: the crested gecko, leopard gecko, and mourning gecko. These species represent different families of the Gekkota infraorder and exhibit different types of sex determination. Gonadal development was examined from the formation of the earliest gonadal ridges through the development of undifferentiated gonadal structures, sex differentiation of gonads, and the formation of testicular and ovarian structures. The study showed that the gonadal primordia of these three gecko species formed on the most dorsally located surface of the dorsal mesentery, and both the coelomic epithelium and the nephric mesenchyme contributed to their development. As in other reptile species, primordial germ cells settled in the gonadal ridges, and the undifferentiated gonad was composed of a cortex and a medulla. Ovarian differentiation started with the thickening of the gonadal cortex and proliferation of germ cells in this region. A characteristic feature of the developing gecko ovaries was the thickened crescent-shaped cortex on the medial and ventral surfaces of the ovaries. The ovarian medulla also grew and exhibited diverse tendencies to form cords. In the leopard gecko, advanced cord-like structures with lumens were observed in the ovaries, which were not seen in the crested gecko. Testicular differentiation was characterized by cortical thinning and the disappearance of germ cells in this region. In the medulla, the development of distinct cords with early lumen formation was noted. A characteristic feature of embryonic gonads was their growth in a horizontal plane. In this study, gonadal development was characterized by several features that are shared by geckos and other reptiles, along with features that are specific only to geckos.

Histological analysis of early gonadal development in three bird species reveals gonad asymmetry from the beginning of gonadal ridge formation and a similar course of sex differentiation.

The developing gonads constitute a valuable model for studying developmental mechanisms because the testes and ovaries, while originating from the same primordia, undergo two different patterns of development. So far, gonadal development among birds has been described in detail in chickens, but literature on the earliest stages of gonadogenesis is scarce. This study presents changes in the structure of the gonads in three species of breeding birds (chicken, duck, and pigeon), starting from the first signs of gonadal ridge formation, that is, the thickenings of the coelomic epithelium. It appears that both gonads show asymmetry from the very beginning of gonadal ridge formation in both genetic sexes. The left gonadal ridge is thicker than the right one, and it is invaded by a higher number of primordial germ cells. Undifferentiated gonads, both left and right, consist of the primitive cortex and the medulla. The primitive cortex develops from the thickened coelomic epithelium, while the primitive medulla - by the aggregation of mesenchymal cells. This study also describes the process of sex differentiation of the testes and ovaries, which is initiated at the same embryonic stage in all three studied species. The first sign of gonadal sex differentiation is the decrease in the number of cortical germ cells and a reduction in cortical thickness in the differentiating testes. This is followed by an increase in the number of germ cells in the medulla. The cortical asymmetry and difference in size between the left and right testes diminishes during later development. However, the differentiating left ovary shows an increase in the number of cortical germ cells and cortical thickness. No regression is seen in the right ovary, although its development is slower. The right ovarian cortex undergoes testis-specific reduction, while the medulla undergoes ovary-specific development. The process of gonadogenesis is similar in the three studied species, with only slight differences in gonadal structure.