AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 1 8-11, Copyright © 1993 by American Physiological Society
A molecular genetic method for genotyping fatty (fa/fa) rats
J. W. Smoller, G. E. Truett, J. Hirsch and R. L. Leibel
Laboratory of Human Behavior and Metabolism, Rockefeller University, New York, New York 10021.
After three decades of physiological research, the precise nature of the
genetic lesion in Zucker fatty (fa/fa) rats remains unknown. Several
methods have been used to identify preobese rats to detect the earliest
phenotypic effects of the fa mutation. Most of these methods have used
phenotypic characteristics that are not reliable until the second week of
life, when increased adiposity is already evident. We have used a
restriction fragment length polymorphism (RFLP) for a human genomic DNA
probe (VC85) that is tightly linked to the fa locus on rat chromosome 5 to
genotype the F2 progeny of a Zucker (13M) x Brown Norway (BN) fa/+ F1
intercross. Sixty-four rats, comprising five litters, were killed at 5-6 wk
of age. DNA was isolated either from tail at age 4-7 days (36 rats) or from
organs at the time of death (28 rats). Adiposity was scored using inguinal
fat pad weight as a percentage of body weight. RFLP analysis was > 99%
accurate in identifying obese (fa/fa) rats. This molecular genetic method
can be used to genotype fatty rats from an appropriate genetic cross at any
age, even prenatally. Moreover, this method can distinguish heterozygous
from homozygous littermates, enabling an analysis of gene dosage effects.
