The most significant linkage for an aerobic running capacity QTL was found on chromosome RNO16. Although the location of the peak in the LOD plot (used to measure genetic linkage) gives the best estimate of the map position for the QTL, confidence intervals constructed on either a one-LOD support interval or an interval showing a two-LOD difference, have a high probability of containing a QTL. Almost 90 percent of the LOD plot for RNO16 was above the suggestive threshold of linkage for a QTL. This broad plateau in the LOD plot on RNO16 between D16Rat32 and D16Arb3 may be the result of multiple aerobic running capacity QTLs that are in relatively close proximity. A suggestive linkage was also found near the p-terminus of chromosome RNO3 with evidence of an interaction between a QTL on RNO16.
The study also revealed that other cardiac trait differences may also contribute to the genetic differences in running capacity. Heart weight and relative heart weight were significantly greater in the DA strain compared to the COP strain From genetic analysis in the population, a heart weight QTL was identified on chromosome RNO8 and relative heart weight QTL on RNO7. Both of these QTL regions co-localized to markers, D7Rat74 and D8Rat23 near putative aerobic running capacity QTLs identified using selective genotyping.
The parental COP and DA strains were not significantly different in body weight; data, however, showed a small but significant negative correlation between body weight and running capacity in the F2 (COP x DA) population; i.e., rats with lower body weights tended to run further. The researchers also identified a body weight QTL located in the same region of RNO8 that contained aerobic capacity and heart weight QTLs whose effects approached the threshold for suggestive linkage. The genetic component of these correlations are likely to stem from either a gene
Contact: Donna Krupa
American Physiological Society