A mesenchymal perspective of müllerian duct differentiation and regression in Amhr2‐lacZ mice

Abstract

The Müllerian ducts give rise to the female reproductive tract, including the Fallopian tubes, uterus, cervix, and anterior vagina. In male embryos, the Müllerian ducts regress, preventing the formation of female organs. We introduced the bacterial lacZ gene, encoding beta-galactosidase (beta-gal), into the AMHR-II locus (Amhr2) by gene targeting in mouse embryonic stem (ES) cells to mark Müllerian duct differentiation and regression. We show that Amhr2-lacZ heterozygotes express beta-gal activity in an Amhr2-specific pattern. In the gonads, beta-gal activity was detected in Sertoli cells of the testes from 2 weeks after birth, and fetal ovaries and granulosa cells of the adult ovary. beta-gal activity was first detected in the rostral mesenchyme of the Müllerian ducts at 12.5 days post coitus (dpc) in both sexes but soon thereafter expression was found along the entire length of the Müllerian ducts with higher levels initially found in males. In females, beta-gal activity was restricted to one side of the ductal mesoepithelium, whereas in males beta-gal expression encircled the duct. beta-gal activity was also detected in the coelomic epithelium at 13.5 and 14.5 dpc. In male embryos, mesenchymal beta-gal activity permitted the visualization of the temporal and spatial pattern of Müllerian duct regression. This pattern was similar to that observed using a Müllerian duct mesoepithelium lacZ reporter, indicating a coordinated loss of Müllerian duct mesoepithelium and Amhr2-expressing mesenchyme.

Focal Müllerian duct retention in male mice with constitutively activated β-catenin expression in the Müllerian duct mesenchyme

“…However, Cre-mediated excision of exon 3 from the floxed allele of β-catenin is likely to occur later, perhaps after MD regression has already started. Expression from the AMHR2 locus begins at E13 (35), and our preliminary results show that the recombined Ctnnb1 Δ(ex3) allele is only detected at E13.5 (Fig. S5B).…”

“…This led us to speculate that the focal MD retention in mutant mice could result from delayed expression of CA β-catenin. Amhr2-Cre is expressed from a knockin mutation of the Amhr2 locus and its expression occurs only when the endogenous AMHR2 is expressed (4,35). However, Cre-mediated excision of exon 3 from the floxed allele of β-catenin is likely to occur later, perhaps after MD regression has already started.…”

Loss of APC function in mesenchymal cells surrounding the Müllerian duct leads to myometrial defects in adult mice

“…Previous studies with the Amhr2-LacZ reporter mouse model showed that this promoter is active for a brief period from embryonic day 12.5 to 15.5 in mesenchymal cells surrounding the Müllerian ducts (Arango et al, 2008;Jamin et al, 2002;Klattig et al, 2007). Notably, in a related reporter model, Amhr2Cre-driven recombination of a Rosa26 reporter (R26R) resulted in β-galactosidase staining of myometrial cells but not in endometrial stromal cells (Arango et al, 2008;Deutscher and Hung-Chang Yao, 2007).…”

“…Amhr2-LacZ animals (Arango et al, 2008;Arango et al, 1999) and Amhr2Cre animals (Jamin et al, 2002) were obtained from Dr RR…”

“…First we established the pattern of expression driven by the promoter of Amhr2 in the uterus by employing previously developed Amhr2-LacZ reporter mice (Arango et al, 2008). As shown in Figure 1A, LacZ expression was limited to the myometrial layer of the uterus.…”