Studying long-distance enhancers of Sox9 in the developing mouse gonad
SOX9 is a transcription factor known to initiate Sertoli cell differentiation and testis development and is expressed throughout life in Sertoli cells. Expression of SOX9 in the early XX gonad can cause female-to-male sex reversal, whereas loss of function mutations of Sox9 in XY animals can cause male-to-female sex reversal. As Sox9 is widely expressed in many tissues and cell types, and it harbour a very big and complex regulatory region of 2MB (also called the “2MB desert”) we initiated an attempt to discover the enhancers that regulate Sox9 expression specifically in the testis. A 3.2 kb enhancer located 13 kb upstream of Sox9 start site was discovered and termed TES (Testis-specific enhancer of Sox9). Although able to completely mimic Sox9 expression pattern in the testis; targeted deletion of this enhancer using the CRISPR/Cas9 technique failed to induce sex reverse and resulted in 55% reduction in Sox9 mRNA levels in the testis. This indicates that although being important, TES may be not the sole enhancer regulating Sox9 expression in the testis. To address that, we performed DNaseI hypersensitivity assay as well as ATAC-seq and H3K27ac ChIP-seq in Sertoli cells to identify potential active enhancers in the upstream 2MB gene desert of Sox9. Progress in identifying those enhancers and studying their functional roles will be presented and discussed.
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