Genetics. 2014 Jul;197(3):885-97. doi: 10.1534/genetics.113.160259. Epub 2014 May 2.

Regulation of sex determination in mice by a non-coding genomic region.

Arboleda VA¹, Fleming A¹, Barseghyan H¹, Délot E², Sinsheimer JS³, Vilain E⁴.

Author information

1: Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088.
2: Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088 Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088.
3: Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088 Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088.
4: Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088 Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088 Department of Urology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7088 evilain@ucla.edu.

Abstract

To identify novel genomic regions that regulate sex determination, we utilized the powerful C57BL/6J-Y(POS) (B6-Y(POS)) model of XY sex reversal where mice with autosomes from the B6 strain and a Y chromosome from a wild-derived strain, Mus domesticus poschiavinus (Y(POS)), show complete sex reversal. In B6-Y(POS), the presence of a 55-Mb congenic region on chromosome 11 protects from sex reversal in a dose-dependent manner. Using mouse genetic backcross designs and high-density SNP arrays, we narrowed the congenic region to a 1.62-Mb genomic region on chromosome 11 that confers 80% protection from B6-Y(POS) sex reversal when one copy is present and complete protection when two copies are present. It was previously believed that the protective congenic region originated from the 129S1/SviMJ (129) strain. However, genomic analysis revealed that this region is not derived from 129 and most likely is derived from the semi-inbred strain POSA. We show that the small 1.62-Mb congenic region that protects against B6-Y(POS) sex reversal is located within the Sox9 promoter and promotes the expression of Sox9, thereby driving testis development within the B6-Y(POS) background. Through 30 years of backcrossing, this congenic region was maintained, as it promoted male sex determination and fertility despite the female-promoting B6-Y(POS) genetic background. Our findings demonstrate that long-range enhancer regions are critical to developmental processes and can be used to identify the complex interplay between genome variants, epigenetics, and developmental gene regulation.