Production of knockout mice for serine racemase and analysis of the function of D-serine in central nerve system

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A large amount of D-serine is present in the brains of human and higher animals. D-Serine is considered to bind to N-methy-D-aspartate subtype of glutamate receptors and to stimulate neurotransmission. D-Serine is considered to be converted from L-serine by serine racemase. However, the functions of serine racemase and D-serine are not well understood. Therefore, we have planed to produce serine racemase-knockout mice for the examination of the consequence of the serine racemase deficiency.In order to produce serine racemase-knockout mice, we screened mouse-genomic library for clones carrying the serine racemase gene and isolated three clones. Upstream and downstream regions of the gene were excised and inserted into the gene-targeting vector containing the neomycin-resistant gene. The constructed targeting vectors were linearized and transfected into mouse embryonic stem (ES) cells. Neomycin-resistant clones were picked up and examined for the homologous recombination with the serine … More racemase gene. The selected ES clones were checked that they retained the normal karyotype. The cells from the three recombinant ES clones were independently inoculated into blastulae from C57BL/6 mice by micromanipulation. The blastulae were inoculated into the uteri of female ICR mice and three chimeric male mice were born. Mating between these chimeric mice and female C57BL/6 mice produced 29 F_1 heterozygotic mice. Brother-sister mating of the F_1 heterozygotic mice produced 65 F_2 mice consisting of 15 serine racemase-deficient homozygotes, 35 heterozygotes and 15 wild-type homozygotes. We are going to observe the development of these mice and examine the level of D-serine in the organs and the serum. Serine racemase expression is going to be determined by real-time PCR and western blotting. In addition, we are going to establish a serine racemase-knockout strain with the genetic background of the C57BL/6 by continuous backcrossing of serine racemase-deficient mice with C57BL/6 mice. Using these mice we try to elucidate the function of serine racemase and D-serine in the central nerve system. Less