Novel Sxr super(a) ES Cell Line Offers Hope for Y Chromosome Gene-Targeted Mice

A mouse targeted for a Y Chromosome gene has not been reported. Because the Y Chromosome is present in only one copy, and most of its genes are critical for germ cell development, such a mouse would likely be infertile. Thus, we describe a new reproductive strategy to enable transmission of targeted Y Chromosome genes to subsequent generations. The strategy uses two segregating copies of Y Chromosome genes to mimic the autosomal condition. To achieve this, we developed a new embryonic stem cell line from the XYSxr super(a) mouse, which carries a duplication of the gene-rich Y Chromosome short arm. Importantly, we demonstrate germ line transmission of the YSxr super(a) chromosome and describe this significant new tool as a practical solution to enable reproduction in mice targeted for Y Chromosome genes.