Maternal and pup genotype contribution to growth in wild-type and tau mutant Syrian hamsters

The single gene mutation tau in the Syrian hamster-apart from its effect on the circadian organization of locomotor activity-has a pronounced influenc e on body weight. In this study we investigate the impact of maternal and p up genotypes at the tau-locus on the growth rate of pups. Homozygous tau mu tant hamsters (circadian period of 20 hours) had lower growth rates and adu lt body weights than wild-type hamsters, whereas heterozygous tau mutants ( circadian period of 22 hours) were intermediate. In addition, heterozygous pups from heterozygous dams grew heavier than those from wild-type and homo zygous dams. The effect of maternal genotype was further evaluated in a cro ss-foster design, where wild-type and homozygous mutant pups were fostered at birth to either wild-type or homozygous mutant dams. At all ages, the ma ternal tau genotype had a negative effect on body weight, whereas the pup t au genotype had a positive effect during the preweaning period and a negati ve effect afterward.