Identification of genetic regions of importance for reproductive performance in female mice.

Both environmental and genetic factors can dramatically affect reproductive performance in mice. In this study we have focused on the identification of genetic regions, quantitative trait loci (QTL), which affect the breeding capacity of female mice. We have identified polymorphic microsatellite markers for the mouse strains used and performed a genomewide scan on 237 females from a gene-segregating backcross between a high breeder and a relatively poor breeder. The high-breeder mouse strain we used is the inbred NFR/N mouse (MHC haplotype H-2q), which has extraordinary good breeding properties. The moderate breeder chosen for F(1) and N2 progeny was B10.Q, which is a genetically well-characterized MHC-congenic mouse of the H-2q haplotype. Each of the 237 females of the N2 generation was allowed to mate twice with MHC-congenic B10.RIII (H-2r) males and twice with B10.Q males. A predetermined number of phenotypes related to reproductive performance were recorded, and these included litter size, neonatal growth, and pregnancy rate. Loci controlling litter size were detected on chromosomes 1 (Fecq3) and 9 (Fecq4). The neonatal growth phenotype was affected by Fecq3 and a locus on chromosome 9 (Neogq1). On chromosome 11 two loci affecting the pregnancy rate (Pregq1 and Pregq2) were identified. Furthermore, on chromosomes 13 and 17 we found loci (Pregq3 and Pregq4) influencing the outcome of allogeneic pregnancy (allogeneic by means of MHC disparity between mother and fetuses). A locus on chromosome 1 affecting maternal body weight was also identified and has been denoted Bwq7. It is well known that reproductive performance is polygenically controlled, and the identification of the major loci in this complex process opens the possibility of investigating the natural genetic control of reproduction.