Kit/stem cell factor receptor-induced activation of phosphatidylinositol 3'-kinase is essential for male fertility.
The c-kit-encoded transmembrane tyrosine kinase receptor for stem cell factor (Kit/SCF-R) is required for normal haematopoiesis, melanogenesis and gametogenesis. However, the roles of individual Kit/SCF-R-induced signalling pathways in the control of developmental processes in the intact animal are completely unknown. To examine the function of SCF-induced phosphatidylinositol (PI) 3'-kinase activation in vivo, we employed the Cre-loxP system to mutate the codon for Tyr719, the PI 3'-kinase binding site in Kit/SCF-R, to Phe in the genome of mice by homologous recombination. Homozygous (Y719F/Y719F) mutant mice are viable. The mutation completely disrupted PI 3'-kinase binding to Kit/SCF-R and reduced SCF-induced PI 3'-kinase-dependent activation of Akt by 90%. The mutation induced a gender- and tissue-specific defect. Although there are no haematopoietic or pigmentation defects in homozygous mutant mice, males are sterile due to a block in spermatogenesis, with initially decreased proliferation and subsequent extensive apoptosis occurring at the spermatogonial stem-cell level. In contrast, female homozygotes are fully fertile. This is the first report so far demonstrating the role of an individual signalling pathway downstream of Kit/SCF-R in the intact animal. It provides the first in vivo model for male sterility caused by a discrete signalling pathway defect affecting early germ cells.
Pubmed ID: 10655061 RIS Download
Amino Acid Substitution | Animals | Apoptosis | Codon | Embryonic and Fetal Development | Enzyme Activation | Exons | Female | Fertility | Genomic Library | Heterozygote | Homozygote | Introns | Male | Mice | Mice, Mutant Strains | Mutagenesis, Site-Directed | Phosphatidylinositol 3-Kinases | Proto-Oncogene Proteins c-kit | Signal Transduction | Stem Cell Factor