Effect of hydrocortisone on the phenotypic expression and inheritance of the Fused gene in mice.

This study was undertaken to examine the effects of hydrocortisone injected into male mice on the phenotypic expression and inheritance of the Fused (Fu) gene in their offspring. Data were obtained indicating that there is a hydrocortisone-susceptible period during spermatogenesis. Hydrocortisone injections of males during this period resulted in a statistically significant decrease in the proportion of phenotypically Fu offspring. Genetic analysis with the use of the closely linked recessive marker tufted (tf) demonstrated that the deficit of phenotypically Fu individuals among offspring is not caused by the differential death of gametes, zygotes or embryos. According to genetic data, this deficit is due to a decrease in the penetrance of the Fu gene and partly to its inherited inactivation. The possible mechanisms of the observed phenomenon are discussed.