Downstream of the “Androgen receptor-bottleneck”: the transcriptional and chromatin landscape of urogenital midline fusion at single cell resolution and its relevance to differences of sex development (DSD)

Differences of sex development (DSD) refer to conditions in which a person is born with reproductive or sexual anatomy that doesn’t fit the typical definitions of female or male. So far 75 disease genes have been associated with DSDs, but currently the majority of patients with DSD do not receive a molecular diagnosis even after Exome sequencing. This represents a huge challenge in clinical DSD-management due to an uncertain individual prognosis. We assume that missing knowledge about the genes and pathways involved in the androgen dependent genital midline closure program contributes significantly to this problem. The recent advances in the field of single-cell genomics have revolutionized how we study development and disease and could also help understanding the pathology of DSD. Here we hypothesize that joint profiling of single-cell transcriptome and chromatin accessibility in the external genital tubercle of a mouse model for DSD (TFM mouse) will reveal critical insights into the development of DSD and the regulatory architecture of the androgen pathway and help identify new disease genes and critical non-coding elements related to DSD. To investigate this hypothesis, we will apply the following three experimental approaches: Objective 1: To generate a joint single-cell transcriptome and chromatin accessibility atlas of external genital development and urethral tube formation in AR knock-out mice (XY TFM). Objective 2: To create an atlas of candidate genes and non-coding regulatory elements potentially associated with DSD Objective 3: To cross-validate candidate genes from the developed mouse reference atlas in DNA-samples established from cultured genital fibroblasts derived from the external genitalia of human DSD-patients by genome DNA sequencing enriched with patients with a pathological APOD assay indicating molecular disruption of cellular androgen signaling. Our study will generate new molecular insights into the development of DSD and identify new disease genes and non-coding enhancer elements that contribute to DSD. Mutations in these non-coding regulatory elements could in principle explain a substantial proportion of so far unresolved cases of DSD.