PARENT SESSION

(W378) THE CHEMICALLY INDUCED MUTATION gcd2 (GERM CELL DEPLETION 2) REDUCES PRIMORDIAL GERM CELL POPULATIONS AND CAUSES INFERTILITY IN MICE.

Reinholdt, Laura ¹, Kamdar, Sonya¹, Munroe, Robert², Schimenti, John ², ¹ The Jackson Laboratory, Bar Harbor, ME² Cornell University, Ithaca, NY

ABSTRACT- gcd2 (germ cell depletion 2) is an induced mutation on mouse Chr 2 isolated in a three-generation screen for recessive infertility. Both male and female gcd2/gcd2 animals are sterile. However the trait is incompletely penetrant ( 65% of gcd2/gcd2 animals exhibit sterility and the remainder are either fertile or sub-fertile) and there is evidence of embryonic lethality. Germ cell numbers in gcd2-/- animals are reduced at birth, indicating that germ cell depletion is due to defects in germ cell migration, proliferation and/or survival during embryonic development. Quantitative analysis of primordial germ cell populations in embryonic gonads from E10.5, E11.5 and E15 was used to establish the developmental timing of germ cell depletion in gcd2/gcd2 embryos. Normal numbers of primordial germ cells were observed in mutant embryos at E10.5 and no ectopic primordial germ cells were found, indicating that germ cell migration is normal in mutant embryos. In mutant E11.5 embryos primordial germ cells were within the genital ridge, in numbers slightly reduced compared to wild type littermates. By E15, primordial germ cell numbers were significantly reduced compared to normal littermates. By recombination mapping, the gcd2 critical region was narrowed to an 800 Mb region on Chr 2, containing three predicted genes. None of these genes are known to be required for the proliferation and/or maintenance of primordial germ cells or stem cells. Sequence analysis of the coding and untranslated regions of each of these genes in gcd2/gcd2 DNA did not reveal a mutation. However, quantitative RT-PCR analyses revealed that the expression of one of the three genes, Lin7c, is significantly down regulated in mutant gonads, suggesting that the gcd2 phenotype is the result of disrupted regulation of Lin7c. (Supported by National Research Service Award GM66650 to LGR)

KEY WORDS: primordial germ cells, germ cells, mutagenesis