Y chromosome of the inbred mouse KK/Ta strain is associated with reduced body size in Y-consomic strains

Findings: In the DH-Chr Y-+/+ background, Y chromosome substitution significantly decreased the body weight in DH-Chr YKK-+/+ and DH-Chr YSJL-+/+ strains, and the DH-Chr YKK-+/+ strain was the lightest among the 17 Y-consomic strains. In the DH-Chr Y-Dh/+ background (Dh/+ mice have skeletal malformations and are usually lighter than +/+ mice), although Y chromosome substitution did not significantly alter the body weight, the DH-Chr YKK-Dh/+ strain was the lightest among the 17 Y-consomic-Dh/+ strains. In the (B6.Cg-Ay x DH-Chr Y) F1-+/+ background, Y chromosome substitution significantly decreased the body weight and length in the (B6.Cg-Ay x DH-Chr YKK) F1 hybrids. In the (B6.Cg-Ay x DH-Chr Y) F1-Ay/+ background (Ay causes obesity and promotes linear growth), Y chromosome substitution significantly decreased body weight and length in the (B6.Cg-Ay x DH-Chr YKK) F1-Ay/+ hybrids.A body-size-reducing effect of the Y chromosome of the KK/Ta mouse strain was observed irrespective of genetic background. The effect was observed in the presence of Dh and Ay, the autosomal dominant mutations, both of which are known to have substantial effects on body size. These results suggest that there are Y-linked genes that control the body size in mice.