Gene Regulatory Networks for Mullerian Duct Regression

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Mammals, including humans, develop progenitor tissues for both male and female reproductive tract organs before fully differentiating into a male or female. The progenitor tissue for the male reproductive tract is known as the Wolffian duct, and the progenitor tissue for the female reproductive tract is the Müllerian duct. The Wolffian duct further differentiates into the vas deferens, epididymis, and seminal vesicle, while the Müllerian duct differentiates into the oviduct, uterus and upper vagina. An essential step in sex differentiation for males is the regression of the Müllerian ducts. This regression initiates with anti-Müllerian hormone (Amh) transcription in the fetal testes about 12.5 days into embryonic development (E12.5) and approaches completion at E17.5. It is known that Müllerian duct regression requires the binding of AMH, after it is released from the fetal testes, to its primary receptor AMHR2 in the Müllerian duct mesenchyme. This is evidenced by experiments in which male knockout mice that did not express either Amh or Amhr2 did not undergo Müllerian duct regression. Thus, Amh/Amhr2 are essential for male sex differentiation. Male patients without functional AMH or AMHR2 have a uterus, a condition known as Persistent Müllerian Duct Syndrome (PMDS), a difference in sex development (DSD). Amhr2 is expressed in the Müllerian duct mesenchyme, Sertoli, Leydig, and postnatal granulosa cells. Transcriptional regulation of Amhr2 has been studied in Sertoli, Leydig, and granulosa cells in vitro. We have described a gene regulatory network (GRN) for Müllerian duct regression. Our GRN for Müllerian duct regression has illuminated the need to identify the Müllerian duct mesenchyme specific transcriptional enhancer for Amhr2. This proposal uses in vivo transgenic mouse assays and ATAC-seq open chromatin assessments in Müllerian duct mesenchyme cells to identify the cis-elements required for Amhr2 transcription for Müllerian duct regression. This knowledge should inform the GRN for Müllerian duct regression and may provide new insights into the genesis of human DSDs.