ABSTRACT
Eg5, a member of the widely conserved kinesin-5 family, is a plus-end-directed motor involved in separation of centrosomes, and in bipolar spindle formation and maintenance during mitosis in vertebrates. To investigate the requirement for Eg5 in mammalian development, we have generated Eg5 deficient mice by gene targeting. Heterozygous mice are healthy, fertile, and show no detectable phenotype, whereas Eg5(-/-) embryos die during early embryogenesis, prior to the implantation stage. This result shows that Eg5 is essential during early mouse development and cannot be compensated by another molecular motor.
Subject(s)
Blastocyst/metabolism , Embryo Loss/genetics , Gene Expression Regulation, Developmental , Kinesins/genetics , Animals , Blastocyst/cytology , Embryonic Development/genetics , Fluorescent Antibody Technique , Heterozygote , Kinesins/metabolism , Mice , Mice, Knockout , Mitosis/genetics , PhenotypeABSTRACT
CUG-BP1/CELF1 is a multifunctional RNA-binding protein involved in the regulation of alternative splicing and translation. To elucidate its role in mammalian development, we produced mice in which the Cugbp1 gene was inactivated by homologous recombination. These Cugbp1(-/-) mice were viable, although a significant portion of them did not survive after the first few days of life. They displayed growth retardation, and most Cugbp1(-/-) males and females exhibited impaired fertility. Male infertility was more thoroughly investigated. Histological examination of testes from Cugbp1(-/-) males showed an arrest of spermatogenesis that occurred at step 7 of spermiogenesis, before spermatid elongation begins, and an increased apoptosis. A quantitative reverse transcriptase PCR analysis showed a decrease of all the germ cell markers tested but not of Sertoli and Leydig markers, suggesting a general decrease in germ cell number. In wild-type testes, CUG-BP1 is expressed in germ cells from spermatogonia to round spermatids and also in Sertoli and Leydig cells. These findings demonstrate that CUG-BP1 is required for completion of spermatogenesis.
Subject(s)
Growth Disorders/congenital , Mutant Proteins/metabolism , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Spermatogenesis/physiology , Animals , Apoptosis , Biomarkers , CELF1 Protein , Cell Survival , Crosses, Genetic , Embryo, Mammalian/abnormalities , Embryo, Mammalian/cytology , Epididymis/abnormalities , Epididymis/cytology , Epididymis/embryology , Female , Gene Expression Regulation, Developmental , Gene Targeting , Genotype , Germ Cells/cytology , Infertility, Male , Male , Mice , Mutant Proteins/genetics , Phenotype , Pregnancy , RNA, Messenger/genetics , RNA, Messenger/metabolism , Testis/abnormalities , Testis/cytology , Testis/embryologyABSTRACT
To investigate the in vivo function of Fas ligand (FasL), we produced a mouse strain with a FasL gene flanked by loxP sequences. Mice with homozygous floxed FasL gene showed no obvious abnormalities. However, germline deletion of the FasL gene, obtained after mating with mice expressing ubiquitous Cre recombinase, resulted in an unexpectedly severe phenotype. FasL(-/-) mice exhibited an extreme splenomegaly and lymphadenopathy associated with lymphocytic infiltration into multiple organs and autoimmune disease. This severe phenotype led to the premature death at 4 mo of age of >50% of the homozygous mice. It stands in sharp contrast with the milder disease observed in gld (generalized lymphoproliferative disease) mice, indicating that the FasL allele of these mice encodes a protein still able to bind, albeit at a very low level, the Fas receptor.
