Mice

All animal experiments were conducted in accordance with the Guide to the Care and Use of Experimental Animals issued by the Canadian Council on Animal Care and with the approval by Animal Research Committee of McGill University. The B6.Y^TIR mouse was established by placing the Y chromosome from a variant of Mus musculus domesticus caught in Tirano, Italy (TIR) onto the C57BL/6 J (B6) genetic background by repeating backcrosses⁹. B6.Y^TIR male mice (N60-65 backcross generations) were crossed with B6 females (Jackson Laboratory, Bar Harbor, ME) to produce XY females and their XX littermates. The day of delivery was defined as 0 dpp. Upon weaning of pups at 20–25 dpp, their ear punches were taken and used for determining their genotypes by PCR amplification of the Y-linked Zfy gene as described previously⁴⁶. All animals were maintained under specific-pathogen-free conditions with a humidity range of 30–60%, a temperature range 21–24 °C, a light cycle of 12 h light: 12 h darkness, and the food and water were provided ad libitum.