No abstract

It is generally considered that, in mammals, the ovary is endowed with a finite number of oocytes at the time of birth. However, studies concerning rodents, lemurs and humans suggest the existence of stem cells from the germline that may be involved in germ-cell renewal, maintaining postnatal follicle development. This type of work on wild species is scarce; therefore the objective of this study was to determine ovarian morphology and the presence of progenitor cells from the germline of three species of phyllostomid bats (Artibeus jamaicensis, Glossophaga soricina and Sturnira lilium). The morphological characteristics of the ovaries and the expression of specific markers of germline cells, stem cells and proliferation cells were analysed. The morphology of the ovaries of the three bat species was similar. A polarised ovary with follicles at different stages of development and groups of cortical cells similar to primordial germ cells were observed. Immunofluorescent analysis showed that these cortical cells express germline, stem-cell and proliferative markers, indicating the identification of germ cells that could maintain pluripotency, as well as being mitotically active. This suggests that in the adult ovary of phyllostomid bats there may be a mechanism for the self-renewal of the germline.

In sheep embryos, steroidogenic activity has been reported as taking place during the period of sexual differentiation. In the case of mouse embryos, the sporadic detection or absence of steroidogenic enzymes suggests that the ovary is inactive. The purpose of this work was to establish if mouse undifferentiated gonads express steroidogenic enzymes in a similar way as in sheep embryos. To know this, we analyzed the mRNA expression pattern of 3β-Hsd1 and P450arom as well as protein expression pattern of 3β-HSD1 and Testosterone in normal undifferentiated and differentiated gonads from both male and female mice embryo. Our data indicate that there is expression of 3β-Hsd1 in XX gonads during gonad differentiation period. Nevertheless the Testosterone which would indicate steroidogenic activity is not produced. Besides, the absence of P450arom indicates that the production of Estradiol as observed in the ovaries of sheep does not occur. The detection of 3β-Hsd1 in the early stages of ovarian development, as well as the absence of Testosterone suggests that XX gonads are not steroidogenic and that 3β-Hsd1 enzyme may play a different role than in the steroidogenesis process.

B6.Y(Tir) (mice with Y chromosome from a strain in Tirano, Italy, and autosomes and X-chromosomes from the B6 strain) mice provide an excellent model for analysing sex development that occurs during gonadal differentiation; however, the molecular mechanisms that contribute to sex reversal are unclear. Our aim has been to establish which molecular events participate in this sex reversal. The pattern of gene expression related to testicular [Sry (sex-determining region of the Y chromosome), Sox9 (Sry-related high-mobility group box gene 9) and Mis (Müllerian-inhibiting substance)] and ovarian [Wnt4 (Wingless-type MMTV (murine-mammary-tumour virus) integration site family, member 4), Rspo1 (cysteine-rich secretory protein containing a thrombospondin type 1 repeat) and Stra8 (stimulated by retinoic acid gene 8)] differentiation was analysed by applying immunofluorescence and real-time RT-PCR (reverse transcription-PCR), focusing on XY gonads from the B6.Y(Tir) mouse, but also analysing the normal strains CD-1 and C57BL/6J (B6). The expression of genes related to the process of sexual differentiation was altered in the case of the B6.Y(Tir) strain, both at the transcript and protein level, inducing differentiation of ovaries and ovotestes, but not the formation of the testes, which were normal. Our results indicate that the expression of testicular genes is inhibited at various levels, permitting the expression of ovarian genes such as Wnt4, Stra8 and Rspo1. However, their activity was not clear when the data were averaged. Correlation analysis indicated that an ovary differentiation pathway is activated when the testicular differentiation pathway is inhibited.