| First Author | Leiter EH | Year | 1993 |
| Journal | Mouse Genome | Volume | 91 |
| Issue | 1 | Pages | 127-29 |
| Mgi Jnum | J:4250 | Mgi Id | MGI:52746 |
| Citation | Leiter EH, et al. (1993) The glucokinase (Gk) gene maps to mouse chromosome 11. Mouse Genome 91(1):127-29 |
| abstractText | Full text of Mouse Genome contribution: THE GLUCOKINASE (Gk) GENE MAPS TO MOUSE CHROMOSOME 11. Edward H. Leiter and Wayne N. Frankel, The Jackson Laboratory, Bar Harbor, ME, 04609, USA. Defects in the glucose sensitivity of pancreatic Beta cells have been postulated as an underlying cause of non-insulin dependent diabetes mellitus (NIDDM). Glucokinase (EC 2.7.1.2) plays a key role in regulation of glucose-stimulated insulin secretion by the pancreatic Beta cell as well as glucose utilization by the liver at physiologic glucose concentrations. Nonsense mutations in the human glucokinase (GCK) gene, which resides on human Chr 7p, have been associated with certain forms of NIDDM [1]. The availability of a cloned rat glucokinase gene [2] gave us the opportunity to define the chromosomal location of the mouse homolog (Gk). Further, since high and low hepatic glucokinase activity variants have been identified in inbred mice [3], we were interested in determining the level of glucokinase activity in NON mice. NON is a recently developed inbred strain selected for high fasting blood glucose level [4]. The NON/Lt substrain is glucose intolerant and exhibits maturity-onset obesity [5]. Evidence suggesting a possible glucokinase gene defect was our observation (unpublished) of an abnormally low glucose-stimulated insulin secretion from perfused islets from young, preobese NON/Lt males. Accordingly, we examined whether this strain represented a low activity variant at the Gk locus. Materials and Methods The Gk gene in C57BL/6J (B6) genomic DNA was distinguished by Southern blot from that of inbred Mus spretus, SPRET/Ei (SPRET), by the presence in B6 but not in SPRET of a 9.4 -10 kb restriction fragment following Sac I digestion and hybridization with pGK.Z9, a 2216 bp Gk cDNA from rat insulinoma kindly provided by Dr. M.A. Magnuson (Vanderbilt University). Genomic DNAs from other inbred strains DBA/2J, C3H/He, SWR/Bm, SJL/Bm, AKR/J, C57L/J were also examined, but no polymorphisms were observed using pGK.Z9 as probe following digestion with eight different 6-base cutting restriction endonucleases. Chromosomal mapping was performed by analysis of 94 DNAs from a (B6 x SPRET)Fl x SPRET first generation backcross progeny. These samples were obtained from the Genetic Mapping Resource of The Jackson Laboratory. The D11Mit1 microsatellite primers were used in PCR to type a B6 versus SPRET allele as described by Dietrich et al. [6]. Mpmv and Pmv endogenous proviral loci, which are present in B6 but absent from SPRET, were typed as present or absent following oligonucleotide hybridization to dried agarose gels as described previously [7, 8, 9]. Glucokinase enzymatic activity was assayed in hepatic cytosols of 8-week-old NON/Lt, CBA/J, and C58/J males as described by Newgard et al [10]. Specific activity (S.A.), expressed as nanomoles glucose phosphorylated/mg protein/min, was corrected for endogenous hexokinase activity by subtracting activity measured at a glucose concentration of 0.5 mM glucose (hexokinase) from total (hexokinase + glucokinase) activity measured at 100 mM glucose. Results and Discussion The mouse Gk gene clearly maps to proximal Chr 11. Gk did not recombine in 92 interspecific backcross progeny (upper 95% confidence limit of 3.5 cM) with the endogenous provirus Pmv-2 [7, 8] and with the microsatellite locus D11Mit1 [6]. These two marker loci, which did not recombine with each other in 94 meioses, reside near the centromeric end of mouse Chr 11, currently shown at 2 cM and 3 cM, respectively on the October, 1992 consensus mouse locus map [11]. Gk exhibited 1/48 recombinants (2.08 +/- 2.06 cM) with another proviral locus, Pmv-22 known to be slightly more distal, but was unlinked (41/92 recombinants) with the Mpmv-2 provirus which sits near the middle of Chr 11 - confirming the proximal position of Gk. Gk was relatively non polymorphic amongst standard inbred strains and thus was not typed in recombinant inbred (RI) strains. These results extend the homology between a segment on the centromeric end of mouse Chr 11 with human Chr 7p. The human homolog of avian erythroblastosis oncogene B, (Erbb in mouse, encoding epidermal growth factor receptor -EGFR in human) maps to 7p12.3-p12.1. The mouse Erbb locus is known to be distal to Pmv-2 from a previous backcross [12], and is probably also distal to Pmv-22 by about 3.5 cM (5/43 RI discordants) as inferred from RI strain data [13]. Thus, the homologous segment appears to span at least 5 cM in mouse. Assay of hepatic glucokinase activity showed that NON/Lt carried the high activity allele (Gka) with a specific activity (= 75) approximately 25% less than the high activity (S.A. = 102) CBA/J reference strain, and more than two-fold higher than that observed in C58/J, the Gkb, low specific activity (= 31) reference strain. Thus, a Gk gene defect is unlikely to account for the Beta cell glucose insensitivity in NON/Lt males. However, since Gk gene expression in pancreatic Beta cells entails alternate mRNA splicing, and since differences in Gk gene transcription rates or mRNA stability appear to account for the differences between high and low activity strains [14], glucokinase enzyme activity in NON/Lt islets should be examined before it is concluded that there are no defects in regulation of this locus at the NON/Lt Beta cell level. Acknowledgements. This work was supported by National Institutes of Health Grant DK36175 and a grant from the Diabetes Research and Education Foundation. The expert technical assistance of Harry Chapman, Steve Langley and Peter Reifsnyder are gratefully acknowledged. We are also grateful to Dr. Edward Birkenmeier and Ms. Lucy Rowe for providing The Jackson Laboratory Gene Mapping Resource DNA panels, and to Dr. Verity A. Letts for typing proviral loci. WNF is a Special Fellow of the Leukemia Society of America, Inc. References. 1. N. Vionnet et. al. (1992) Nature 356: 721-722. 2. M. Magnuson et. al. (1989) J. Biol. Chem. 264: 15936-15942. 3. D. Coleman (1977) Biochem. Genet. 15: 297-305. 4. S. Makino et. al. (1980) Exp. Anim. 29: 1-8. 5. Committee on Immunologically Compromised Rodents (1989). In National Research Council (eds). Immunodeficient Rodents. National Academy Press, Washington, D.C., pp. 103-104. 6. W. Dietrich et. al. (1992) Genetics 131: 423-447. 7. W. Frankel et. al. (1989) J. Virol. 63: 3810-3821. 8. W. Frankel et. al. (1990) Genetics 124: 221-236. 9. A. Messer et. al. (1992) Genomics 13: 797-802. 10. C. Newgard et. al. (1983) J. Biol. Chem. 258: 8046-8052. 11. A. Hillyard et. al. (October, 1992.) The Jackson Laboratory 12. W. Frankel et. al. (1992) Mamm. Genome 2: 110-122. 13. B. Taylor (1989) In Lyon, M.F. and Searle, A.G. (eds). Genetic Variants and Strains of the Laboratory Mouse. University Press, Oxford, 2nd ed. pp 773-796. 14. R. Middleton et. al. (1992) Comp. Biochem. Physiol. 102B: 337-342. |
