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(138) GENOME-WIDE MUTAGENESIS SCREEN FOR GENES INVOLVED IN SEX DETERMINATION AND TESTIS FUNCTION. Weiss, Jeffrey1, Hurley, Lisa1, Barrett, Timothy1, Tong, Minghan1, Jameson, J. Larry1, 1 Northwestern University, Chicago, IL ABSTRACT- The embryonic gonad is remarkable in that it remains bipotential until mid-gestation, at which time the presence or absence of Sry expression determines whether the gonad will develop as a testis or an ovary. Despite the identification of Sry as the male-determining gene over a decade ago, much remains unknown about the subsequent genetic pathways that control male/female sex determination. In order to identify other genes in this pathway, we have initiated a three generation genome-wide mutagenesis screen for genes involved in sex determination. In addition, collateral screens allow for the identification of genes involved in development of the external genitalia and testis function. ENU mutagenesis is performed within the Northwestern Center for Functional Genomics. Third generation (G3) mice, which can exhibit recessive traits (homozygotes), are created by back-crossing G2 females to G1 fathers (heterozygotes). At weaning, G3 mice are examined for genitourinary malformations and assigned phenotypic sex. To detect sex reversal, tail clips are obtained at 6 weeks of age and the presence or absence of Sry (genotypic sex) is determined by PCR using genomic DNA extracted from the tails. G2 males are also sacrificed for histological examination of the testis, and sperm is collected for identification of defects in sperm number, motility and morphology. To date, we have screened >7000 G3 mice for sex reversal and >600 G2 males for testis defects. Eight potential mutants (putants) have been identified, of which one is recessive and seven are dominant. One putant (G3) has a shortened ano-genital distance and defects in development of the peri-anal region. One putant (G2) has incomplete regression of the Mullerian structures and an indeterminate gonad on the right side. The remaining putants have testis defects that include loss of germ cells, Sertoli cell only syndromes, and overt hypogonadism. Heritability has been established for the G3 mutant and the remaining putants are currently being assessed. All heritable mutants will be genetically mapped to low resolution and made available for distribution to the scientific community. This center is supported by NIH grant U01 HD043425-01 and was funded as part of an NIH initiative to determine the function of mammalian genes. KEY WORDS: enu, development, sex, gonad |
