| Abstract: | Mammalian sexual fate is determined by the presence or absence of sex determining
region of the Y chromosome (Sry) in the “bipotential” gonads.
Recent studies have demonstrated that both male and female sexual development are induced
by distinct and active genetic pathways. Breeding the Y chromosome from Mus m.
domesticus poschiavinus (POS) strains into C57BL/6J (B6J) mice
(B6J-XYPOS) has been shown to induce sex reversal (75%: bilateral ovary, 25%:
true hermaphrodites). However, our B6N-XYPOS mice, which were generated by
backcrossing of B6J-XYPOS on an inbred B6N-XX, develop as males (36%: bilateral
testis with fertility as well as bilateral ovary (34%), and the remainder develop as true
hermaphrodites. Here, we investigated in detail the expressions of essential sex-related
genes and histological features in B6N-XYPOS mice from the fetal period to
adulthood. The onsets of both Sry and SRY-box 9 (Sox9) expressions as determined
spatiotemporally by whole-mount immunohistochemistry in the B6N-XYPOS gonads
occurred 2–3 tail somites later than those in B6N-XYB6 gonads, but earlier than
those in B6J-XYPOS, respectively. It is possible that such a small difference
in timing of the Sry expression underlies testicular development in our
B6N-XYPOS. Our study is the first to histologically show the expression and
ectopic localization of a female-related gene in the XYPOS testes and a
male-related gene in the XYPOS ovaries. The results from these and previous
experiments indicate that the interplay between genome variants, epigenetics and
developmental gene regulation is crucial for testis development. |
