Inbreeding depression for litter size in two mice lines under divergent selection for environmental birth weight...

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Population Genetics

Background:

• Inbreeding depression (ID) reduces survival and fertility, with impacts varying across populations.
• Divergent selection for environmental birth weight variability created high (H-Line) and low (L-Line) variability mouse lines.
• The L-Line exhibits superior robustness compared to the H-Line.

Purpose of the Study:

• To estimate inbreeding depression (ID) in litter size (LS) using genomic and pedigree data in H-Line and L-Line mice.
• To compare the impact of different inbreeding measures on LS in divergently selected mouse lines.
• To identify genomic regions and inbreeding patterns associated with ID in selected mouse populations.

Main Methods:

• Genomic DNA from 1587 mice across 26 generations was analyzed using high-density SNP arrays.
• Litter size data from 732 L-Line and 648 H-Line animals were used.
• Pedigree (FPED) and various genomic inbreeding coefficients (FNEJ, FL&H, FVR1, FVR2, FYAN, FROH, FHBD) were calculated and standardized.

Main Results:

• Genomic inbreeding negatively affected litter size in both lines, with a stronger impact in the H-Line (m=-3.71 to -5.09) than the L-Line (m=-3.52 to -4.55).
• Significant ID effects were localized to CHR13 in the H-Line and CHR1 and CHR9 in the L-Line.
• Recent runs of homozygosity (ROH) and homozygosity by descent (HBD) segments negatively impacted LS, while older segments showed positive effects, particularly in the L-Line.

Conclusions:

• The L-Line demonstrates higher robustness to inbreeding depression compared to the H-Line.
• Chromosomes 1, 9, and 13 are identified as key regions for future gene association studies related to inbreeding depression.
• Understanding the influence of ROH and HBD age is crucial for managing inbreeding in selective breeding programs.