Platform Session 13. Sexually Dimorphic Development of Reproductive Organs in Embryos
Monday, July 25, 2005
2:00 PM–4:00 PM
Location: CCQ 208AB
(100) THE ROLE OF BETA-CATENIN ON THE DEVELOPMENT OF THE MULLERIAN DUCT IN MOUSE EMBRYOS.
Deutscher, Erica1, Aardema, Jorie 1, Yao, Humphrey1, 1 University of Illinois at Urbana-Champaign, Urbana, IL
ABSTRACT- The Müllerian duct (MD) is the embryonic precursor of the female reproductive tract that differentiates into oviduct, uterus, and upper part of the vagina in adults. Emerging genetic evidence in mice indicate that various signaling pathways, such as WNT, play critical roles in early MD formation and patterning. WNT4 is required for initial formation of the MD, WNT7a is responsible for uterine differentiation, and WNT5a is involved in generation of uterine glands. One drawback of these studies is that these WNT ligands could function redundantly and make it difficult to interpret results. To understand how WNT signaling controls MD development, beta-catenin, the downstream signaling molecule of the canonical WNT ligands, was inactivated. Because beta-catenin knockout embryos die before organogenesis, a conditional Cre/loxP approach was used to inactivate beta-catenin specifically in the mesonephros, where the MD resides. We took advantage of the anti-Müllerian hormone receptor-2 Cre model (Amhr2-cre), which targets Cre recombinase activity in the mesonephros. It was essential to determine cellular contexts and a time course of Cre recombinase activity in the MD to identify specific tissues that will be affected. Therefore, an Amhr2-cre line was crossed to a Z/EG reporter line, where green fluorescent protein (GFP) appears only in cells expressing the Cre recombinase. Cells positive for GFP (or Cre activity) were found in the mesenchyme surrounding the MD at initial stages and became restricted to the mesenchyme in the anti-mesentery aspect of the duct just before birth. Next, we generated the conditional knockout of beta-catenin and found that at birth, inactivation of beta-catenin in the mesenchyme of the MD led to significant hypotrophy of uterine horns (only one fourth of diameter of the wild type) due to a decrease in the mesenchymal layer. Wild type littermates had uterine horns that exhibited the normal S-shaped curving from the oviduct to the vagina while uterine horns from conditional beta-catenin null female remained at an undifferentiated stage with a linear tubule structure. These results demonstrate that beta-catenin is essential for proper differentiation and maintenance of the MD mesenchyme, which could be a target of WNT signaling in the patterning of the MD. (Supported by NIH-HD46861).
KEY WORDS: Mullerian duct, WNT, beta-catenin