In a QTL mapping study with an F2 population of mice,
we
have shown that one or more sex-linked factors account for a large part
of the divergence between mouse lines selected for high and
low body weight. Here, we describe a study undertaken to map the putative
X-linked quantitative
trait loci (QTLs) by backcrossing segments of chromosome from the high
line
onto an inbred line
derived from the low line, thereby removing possible contributions from
the autosomes and linked
segments of the X chromosome. Sublines containing a regional at the
proximal end of the X
chromosome were found to be associated with large differences in body
weight, and to account for
almost all the difference between the lines. A Markov chain Monte
Carlo based multipoint linkage
analysis incorporating the available marker and phenotypic information
from the backcross
pedigree was used to map the QTL to a region of about 6 cM. There was no
evidence for QTLs
elsewhere on the chromosome. The estimated QTL effect is approximately
20% of mean body weight in males and females at 10 weeks. From results
obtained from
this study and the
accompanying F2 analysis, we conclude the presence of a single
factor for body weight localizing
to about position (±SE) 26·4±1·2 cM on the
X chromosome, which increases body weight by
approximately 18% at 10 weeks. A strategy to positionally clone the QTL
is discussed.
Quantitative trait loci mapping for canine hip dysplasia and its related traits in UK Labrador Retrievers
