International Mammalian Genome Society

The 14th International Mouse Genome Conference (2000)

G16. High Resolution Mapping and Characterisation of an X-linked QTL Influencing Body Weight in Mice

Xiaojun Liu, Peter Keightley
Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, Scotland, UK


An X-linked QTL causing a ~20% of thhe difference for body weight has been described previously. A likelihood analysis incorporating available markers and phenotypic information from a progeny test has mapped the QTL to a ~2cM region flanked by markers ~5cM apart. To facilitate the positional cloning of the locus, we attempted to build a high resolution map and to narrow down the target region. Firstly, all of the microsatellite markers in the target region available from public databases were tested at high resolution using animals containing the high (H) QTL allele or low (L) allele, but all of them were non informative. Secondly, 380 RAPD (Random Amplified Polymorphic DNA) primers and 64 pairs of AFLP (Amplified Restriction Fragment Polymorphism) primers were tested, but no polymorphic markers were found in the target region. Then alleles of genes and some STSs that mapped in or closed to the target region were sequenced. Alignment of the sequences generated from forward and reverse primers using H and L DNA revealed no differences in more than 20,000bp. Our failure to detect any polymorphisms seems to reflect a real lack of variation in the region. It is therefore possible that the QTL represents a relatively new mutation in a segment of the genome with recent common ancestry.

Meanwhile, an experiment based on a partially congenic high lines (H and L), differing for a segment containing the QTL was set up to investigate the phenotypic effect of the QTL on growth-related traits. Seventeen traits including body weight, body length, weights of various organs and food intake at different ages were measured. Analysis of the data shows that the QTL has significantly effect on nearly all of the traits. Effect on body weight at all ages is ~20%, and the effect on early growth rate is higher than late growth rate. Effects on the weights of internal organs are larger than that on body weight, but the effect on body length is smaller than that for body weight. Feed is converted to body mass more efficiently in the H line than the L line.


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