Anti-Müllerian hormone (AMH) produced in the developing testis induces the regression of
the Müllerian duct, which develops into the oviducts, uterus and upper vagina. In our true
hermaphrodite mouse with an ovary on one side and a testis on the other (O/T), the oviduct
and uterus are present only on the ovary side, and nothing derived from the Müllerian duct
is present on the testis side. Here, we investigate the mechanism underlying the
unilateral Müllerian duct regression and the mode of AMH signaling, by performing
immunohistology, Western blotting, and organ culture analyses. The histological analysis
revealed that during the start of the Müllerian duct regression, the duct in the O/T mice
was clearly regressed on the AMH-positive testis side compared to the AMH-negative ovary
side. The immunohistochemistry showed a diffuse immunoreaction of AMH in the interstitium
surrounding the testis cord and boundary region between the testis and mesonephros,
especially in the cranial portion. Western blotting revealed that the amount of AMH in the
cranial half of the mesonephros was larger than that in the caudal half. AMH injected into
the gonads in organ culture induced the regression of the Müllerian duct via the
interstitium of the organ. These results suggest that AMH acts on the Müllerian duct in
male mice by exuding into the interstitium surrounding the testis cord and infiltrating
through the cranial region from the testis to the mesonephros.
Running Head: CULTURE SYSTEM OF UNDIFFERENTIATED GONAD (40/40 characters) immature gonads (6 ts). These results show that our gonadal organ culture system is useful for elucidating the regulation mechanism of Sry expression in undifferentiated bipotential gonads.
C57BL/6J-XY
POS
(B6J-XY
POS
) mice, which have the Y chromosome
derived from
Mus musculus poschiavinus
on a B6J genetic background, form
ovotestes or ovaries. Previously, we replaced the genetic background of
B6J-XY
POS
mice with B6N and found that individuals with testes also appeared
in addition to those with ovaries or ovotestes. To investigate the effect of the B6J
genetic sequence on the testis differentiation, the genetic background of
B6N-XY
POS
mice was replaced with B6J again. The recovery of the B6J genetic
background significantly decreased the incidence of testes; only ovaries developed. These
results indicate that the testicular differentiation process tends to be perturbed
especially in the B6J substrain. This shows the importance of substrain differences in
mice usually treated as B6 collectively.
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