Vasopressin gene expression is attenuated in the fetal Brattleboro rat

Due to a genetic defect the homozygous Brattleboro rat is unable to synthesize vasopressin gene products but still transcribes a mutant vasopressin mRNA from the gene. To study the influence of vasopressin gene products on the development of vasopressin gene expression, vasopressin mRNA levels of the supraoptic and paraventricular nucleus were measured at fetal day 20, postnatal day 1, 15 and 30 in the Wistar rat and in the heterozygous and homozygous Brattleboro rat by Northern blot analysis and in situ hybridization. In the homozygous Brattleboro rat of fetal day 20 and postnatal day 1, no or minute amounts of vasopressin mRNA were detectable but vasopressin mRNA was readily detectable at postnatal day 15 and 30. The Wistar rat and heterozygous Brattleboro rat had abundant vasopressin mRNA at fetal day 20 with increasing amounts towards postnatal day 30. The results indicate that vasopressin gene expression in the development of the homozygous Brattleboro rat is attenuated, possibly due to the absence of vasopressin gene products.