| First Author | Danciger M | Year | 1993 |
| Journal | Mouse Genome | Volume | 91 |
| Issue | 2 | Pages | 320-22 |
| Mgi Jnum | J:12762 | Mgi Id | MGI:60981 |
| Citation | Danciger M, et al. (1993) A second mouse glutamic acid decarboxylase gene (Gad-2) maps proximal to Gad-1 on chromosome 2. Mouse Genome 91(2):320-22 |
| abstractText | Full text of Mouse Genome contribution: A Second Mouse Glutamic Acid Decarboxylase gene (Gad-2) Maps Proximal to Gad-1 on Chromosome 2. Michael Danciger (l, 2), M. Charlene Adamson (3), Debora B. Farber (1) and Christine A. Kozak (3). 1-Jules Stein Eye Institute, UCLA Medical School, Los Angeles, CA 90024-7008; 2-Loyola Marymount University, Los Angeles, CA 90045; 3-NIAID, NIH, Bethesda, MD 20892. Introduction Glutamic acid decarboxylase (GAD) catalyzes the rate-limiting step in the production of the major known inhibitory neurotransmitter gamma-aminobutyric acid (GABA). There are two distinct human glutamate decarboxylases referred to as GAD67 and GAD65 (1) encoded by two distinct genes (GAD1 and GAD2) which have recently been mapped to human chromosomes 2q31 and 10p11.23, respectively (2). The GAD enzyme is also expressed in pancreatic beta cells, and has been shown to be a target of autoantibodies in people who later develop insulin dependent diabetes mellitus (IDDM) (3). With regard to IDDM, an autoimmune pathogenic role for GAD65 due to molecular mimicry has been suggested, because it shares some amino acid sequence homology with the P2-C protein of Coxsackie viruses, often suggested as environmental triggering agents of IDDM (2). A few years ago, a feline cDNA for GAD67 was used to clone BALB/c mouse genomic DNA fragments which were used as probes to map the murine Gad-1 gene distal to the Abl gene on mouse Chr 2 (4). This region of mouse Chr 2 is homologous with human 2q (where GAD1 is localized). In the same study it was shown that a Gad-1 pseudogene (Gad-1ps) localized to mouse Chr 10. In this paper we present data which confirms the mapping of Gad-1ps and Gad-1, and localizes the Gad-2 gene to mouse Chr 2 proximal to the Abl gene. Materials and Methods Mice. Two multilocus crosses were typed. In the first cross, NFS/N females were mated with M. spretus males and the F1 females mated with M. spretus males or C58/J males (5). In the second cross, NFS/N or C58/J females were mated with M. m. musculus males and the F1 females mated with M. m. musculus males (6). Southern blotting. Southern blot analysis of progeny DNAs was carried out as described previously (7). Mice were typed for the Gad-2 gene with a 1.3 kb BamHI/Stu1 fragment (GAD2BS) of the cDNA encoding the complete GAD2 protein (1). The fragment begins near the ATG start of the cDNA and includes about three quarters of the coding region. A 1.5 kb Ncol fragment (GAD1N) of the cDNA encoding the GAD1 protein was used to probe for Gad-1 and Gad-1ps. This fragment consists of about 80% of the coding region and starts at the 5' ATG. Both probes were kindly provided by Dr. Allan Tobin (UCLA). Progeny of the two crosses have been typed for over 440 genetic markers distributed over the mouse genome including Abl (Abelson oncogene), Sfpi-1 (SFFV proviral integration-1), Ifg (interferon gamma) and Tra-1 (tumor rejection antigen [gp96]). For the musculus cross, Abl was typed as described by Hunt et al. (8), Sfpi-1 as described by Paul et al, (9), and Ifg and Tra-1 as described by Kozak et al, (6). In the spretus cross, Sfpi-1, Ifg, and Tra-1 were typed following digestion with Bg/ll, BamHI and Pstl respectively. Vim (vimentin) was typed in the spretus cross following digestion with EcoRI using a probe obtained from Oncor (Gaithersberg, MD). Results and Discussion GAD2BS identified fragments of 25 kb in M. spretus and 21 kb in NFS/N and C58/J DNAs digested with BamHI. In the M. m. musculus cross, GAD1N identified multiple fragments; we scored for the presence or absence of a 4.0 kb BamHI fragment in NFS/N and C58/J which identified Gad-1. In the spretus cross, GAD1N identified multiple bands; after digestion with PvuII, and NFS/N band of 15.0 kb and a M. spretus band of 9.2 kb identified the Gad-1ps pseudogene and an NFS/N band of 4.1 kb and an M. spretus band of 4.4 kb identified the Gad-1 gene. C58/J DNAs produced 15.0 and 4.1 kb fragments corresponding to Gad-1 and Gad-1ps, respectively. The inheritance of Gad-1ps was compared with the segregation of Tra-1 and Ifg and the following order on mouse Chr 10 was determined: Tra-1 - Gad-1ps - Ifg (Table 1). The inheritance of the Gad-2 gene was compared with the segregation of other markers typed in this cross and results showed linkage to markers on proximal Chr 2 with the gene order: Vim - Gad-2 Ã Abl - Gad-1 - Sfpi-1 (Table 2). These results confirm and extend previous genetic studies in which a mouse Gad-1 probe was used to map Gad-1 to Chr 2 using a M. spretus backcross and Gad-1ps to Chr 10 using RI strains (4). Our results additionally demonstrate that Gad-2 and Gad-1 are linked on mouse Chr 2 although the human homologs map to chromosomes 10 and 2 respectively (2). Our map location of Gad-2 proximal to Abl is consistent with the human map location since this region of Gad-2 contains at least two other genes, Vim and Itih2, with human chromosome 10 homologs (11, 12). Our data demonstrates that Gad-2 lies within this same region of homology. References 1. Erlander, M.G. et al., 1991. Neuron 7:91-100. 2. Bu, D.-F. et al., 1992. Proc. Natl. Acad. Sci. USA 89:2115-2119. 3. Baekkeskoz, S. et al., 1990. Nature 347:151-156. 4. Brilliant, M.H. et at., 1990. Genomics 6:115-122. 5. Adamson, M.C. et al., 1991. Virology 183:778-781. 6. Kozak, C.A. et al., 1990. Genomics 8:519-524. 7. Danciger, M. et al., 1990. Exp. Eye Res. 51:185-189. 8. Hunt, C.R. et al., 1993. Genomics 16:193-198. 9. Paul, R. et al., 1991. J. Virol. 65:464-467. 10. Green, E.L, 1981. Genetics and Probability in Animal Breeding Experiments, pp 77-113. Macmillan, NY. 11. Siracusa, L.D. et al., 1991. Genetics 128:813-821. 12. Salier, J.P. et al., 1992. Genomics 14:83-88. Table 1 Ã Segregation of Gad-1ps alleles on Chromosome 10 with alleles of Tra-1 and Ifg in the cross: (NFS/N x M. spretus)F1 x M. spretus or C58/J(5). Loci: Tra-1: +a; Gad-1ps: +; Ifg: +; No. of progeny: 37 Loci: Tra-1; --; Gad-1ps: --; Ifg: --; No. of progeny: 43 Loci: Tra-1: +; Gad-1ps: +; Ifg: --; No. of progeny: 3 Loci: Tra-1: --; Gad-1ps: --; Ifg: +; No. of progeny: 2 Loci: Tra-1: +; Gad-1ps: --; Ifg: --; No. of progeny: 6 Loci: Tra-1: --; Gad-1ps: +; Ifg: +; No. of progeny: 7. % Recombination: (Tra-1, Gad-1ps) = 13/98 = 13 +/- 3.4b (Gad-1ps, Ifg) = 5/98 = 5 +/- 2.2 (Tra-1, Ifg) = 18/98 = 18 +/- 3.9 a-Scored as heterozygous (+) or hornozygous (--) for the parental allele. b-Percent recombination and standard errors were calculated according to Green, 1981 (10) from the number of recombinants; all distances are significant to the 0.05 level. Table 2 - Segregation of Gad-2 alleles on Chromosome 2 with alleles of Vim, Gad-1, Abl and Sfpi-1 in the crosses: (NFS/N x M.spretus)Fl x M. spretus or C58/J (5); (NFS/N or C58 x M. m. musculus)Fl x M. m. musculus (6). Loci: Vim: Nda; Gad-2: ND; Abl: +b; Gad-1: +; Sfpi-1: +; No. of progeny: musculus cross: 21 Loci: Vim: +; Gad-2: +; Abl: +; Gad-1: +; Sfpi-1: +; No. of progeny: spretus cross: 24 Loci: Vim: ND; Gad-2: ND; Abl: --; Gad-1: --; Sfpi-1: --; No. of progeny: musculus cross: 25 Loci: Vim: --; Gad-2: --; Abl: --; Gad-1: --; Sfpi-1: --; No. of progeny: spretus cross: 18 Loci: Vim: ND; Gad-2: ND; Abl: +; Gad-1: +; Sfpi-1: --; No. of progeny: musculus cross: 0 Loci: Vim: +; Gad-2: +; Abl: +; Gad-1: +; Sfpi-1: --; No. of progeny: spretus cross: 0 Loci: Vim: ND; Gad-2: ND; Abl: --; Gad-1: --; Sfpi-1: +; No. of progeny: musculus cross: 3 Loci: Vim: --; Gad-2: --; Abl: --; Gad-1: --; Sfpi-1: +; No. of progeny: spretus cross: 2 Loci: Vim: ND; Gad-2: ND; Abl: +; Gad-1: --; Sfpi-1: --; No. of progeny: musculus cross: 7 Loci: Vim: +; Gad-2: +; Abl: +; Gad-1: --; Sfpi-1: --; No. of progeny: spretus cross: 7 Loci: Vim: ND; Gad-2: ND; Abl: --; Gad-1: +; Sfpi-1: +; No. of progeny: musculus cross: 4 Loci: Vim: --; Gad-2: --; Abl: --; Gad-1: +; Sfpi-1: +; No. of progeny: spretus cross: 7 Loci: Vim: +; Gad-2: +; Abl: --; Gad-1: --; Sfpi-1: --; No. of progeny: spretus cross: 1 Loci: Vim: --; Gad-2: --; Abl: +; Gad-1: +; Sfpi-1: +; No. of progeny: spretus cross: 1 Loci: Vim: +; Gad-2: --; Abl: --; Gad-1: --; Sfpi-1: --; No. of progeny: spretus cross: 1 Loci: Vim: --; Gad-2: +; Abl: +; Gad-1: +; Sfpi-1: +; No. of progeny: spretus cross: 1 Loci: Vim: +; Gad-2: --; Abl: --; Gad-1: +; Sfpi-1: +; No. of progeny: spretus cross: 1. % Recombination: (Vim, Gad-2,) = 3/63 = 5 +/- 2.7c; 4/77d= 5 +/- 2.5 (Gad-2, Abl) = 2/63 = 3 +/- 2.2; 4/85e = 5 +/- 2.3 (Abl, Gad-1) = 15/63 + 11/60 = 26/123 = 21 +/- 3.7 (Gad-1, Sfpi-1) = 2/63 + 3/60 = 5/123 = 4 +/- 1.8 a-ND = not done b-Scored as heterozygous (+) or homozygous (--) for the parental allele. c-Percent recombination and standard errors were calculated according to Green, 1981 (10) from the number of recombinants; all distances are significant to the 0.05 level. d-There was 1 recombinant in 14 additional mice scored for Vim and Gad-2 but not for the other markers. e-There were 2 recombinants in 22 additional mice scored for Gad-2 and Abl but not for the other markers. |
