| First Author | Klocke R | Year | 1992 |
| Journal | Mouse Genome | Volume | 90 |
| Issue | 3 | Pages | 433-35 |
| Mgi Jnum | J:2513 | Mgi Id | MGI:51036 |
| Citation | Klocke R, et al. (1992) Chromosomal mapping of muscle-expressed sodium channel genes in the mouse. Mouse Genome 90(3):433-35 |
| abstractText | Full text of Mouse Genome contribution: CHROMOSOMAL MAPPING OF MUSCLE-EXPRESSED SODIUM CHANNEL GENES IN THE MOUSE. R. Klocke(1), K. Kaupmann(1*), A.L. George Jr.(2), R.L. Barchi(3) and H. Jockusch(1). 1Developmental Biology Unit, W7, University of Bielefeld, POB 10 01 31, D-W4800 Bielefeld 1, Fed. Rep. Germany; FAX (521) 106-5654; 2Dept. of Medicine/Nephrology, S-3223 MCN, Vanderbilt University School of Medicine. 21st and Garland Avenues, Nashville, TN 37232, USA; FAX (615) 343-7156. 3David Mahoney Institute of Neurological Sciences, University of Pennsylvania, The School of Medicine, Philadelphia, PA 19104-6074, USA; FAX (215) 573-2015. Introduction The generation and propagation of action potentials in muscle cells and neurons of vertebrates depend on Na+-channels, the principal subunit of which is the alpha-subunit [3]. At least five different alpha-subunits have been cloned and molecularly characterized in the rat alone. Of the relevant genes (using the nomenclature for the mouse), Scn1a, 2a and 3a are expressed in the brain, whereas Scn4a and an additional gene herewith termed Scn5a are expressed in muscle [8]. Scn4a is the gene for the TTX sensitive Na+-channel SkM1 of adult skeletal muscle, whereas Scn5a codes for the TTX insensitive Na+ channel SkM2 [5] characteristic of neonatal and denervated skeletal as well as of cardiac muscle. The human muscle diseases hyperkalaemic periodic paralysis [10] and paramyotonia congenita [9] are due to mutations in the SCN4A gene (the homolog of mouse Scn4a) on Chr 17 [4]. We have mapped the muscle-expressed Na+ -channel genes Scn4a and Scn5a in the mouse to compare their chromosomal locations to those of the brain expressed isoforms [7] and to relate them to the syntenlc regions conserved between mouse and man. After the completion of this work, the localization of Scn4a on mouse Chr 11 has been reported [1], at a position predicted on the basis of conserved synteny. Material and Methods Mice. An interspeciflc mouse backcross of Mus musculus and Mus spretus, strain SEG (C57BL/6J wr/ + x Mus spretus +/+) F1 wr/ + x C57BL/6J wr/+ was used as described in Ref. 6. Probes. Rat- SkM1: cDNA probe 6-2-1 (nt. 2820-3580; interdomain II-III region) and the genomic probe 14.1/1.7 (5' untranslated sequences). Rat-SkM2: isoform specific cDNA probe 15-2-1 (nt. 6203-7075; 3' untranslated region). Marker probes are described in Ref. 6 except for pA29, ventricular myosin alkali light chain (MLC1v), kindly provided by M. Buckingham, Paris [2]. Isolation and restriction of genomic DNA and Southern hybridization were done by standard procedures. Results and Conclusions Restriction fragment length variants (RFLVs) specific for Mus spretus (SEG) were screened for by Southern hybridization using Bam HI, Bgl II, Eco RI, Msp I, Pvu II, Rsa I, Sal I, Sca I, Sma I, Sst I, Taq I and Xba I (Table 1). The SkM1 probe 6-2-1 detected an SEG specific Sst I RFLV that co-segregated with markers on Chr 11 , and, at low stringency, an additional Pvu II fragment "a" that localized to Chr 2. The position of sequences on Chr 11 detected with probes 6-2-1 and 14.1/1.7, defines the locus for the Na+ -channel SkM1 (Fig. lb), confirming Ref. l with a different set of markers. With the SkM2 probe defining gene Scn5a, only one SEG specific fragment was detected and this showed close linkage (7 recombinants in 77 meioses; lod score 13) with Mylc on Chr 9 (Fig. 1a). An additional Pvu II RFLV "b" detected with 6-2-1 cosegregated (1 recombinant in 77 meioses) with the SkM2 specific RFLV and was thus localized to Chr 9, indicating either cross-hybridization to Scn5a (and one intragenic recombination event) or another Scna gene closely linked to Scn5a. In either case, the main muscle-expressed genes for Na+-channels are not clustered. Scn5a does not fall into an established region of conserved man/mouse synteny, but is located close to a region, extending from Acy-1 (proximal) to Mylc, with homology to human Chr 3p. Table 1: Restriction fragments (sizes in kb) detected with Na+-channel probes. Channel, Probe: SkM1, 6-2-1 (Scn4a); Nuclease: Sst I; SEG: 5.0; C57BL/6J: 4.4/3.3; Chr: 11; Nuclease: Pvu II; SEG: 14.5 (a); C57BL/6J: 24.0 (a); Chr: 2; Nuclease: Pvu II; SEG: 3.5 (b); C57BL/6J: 3.0 (b); Chr: 9. Channel, Probe: SkM1, 14.1/1.7 (Scn4a); Nuclease: Bam HI; SEG: 1.05/1.35; C57BL/6J: 2.4; Chr: 11; Nuclease: Sca I; SEG: 25.0; C57BL/6J: 7.0; Chr: 11. Channel, Probe: SkM2, 15-2-1 (Scn5a); Nuclease: Pvu II; SEG: 7.8; C57BL/6J: 6.6; Chr: 9. Probe 6-2-1: The Pvu II fragments (a) could only be detected under conditions of low stringency (final wash: 0.5 x SSC, 0.1% SDS, 55 degrees C) and probably represent cross-hybridization with one of the brain-expressed genes. Fig. 1: Map positions of muscle-expressed Na+-channel genes Scn4a and Scn5a. Fig. 1 Legend: Distances in cM +/- S.D.M. - a: Tma, gene for alpha-tropomyosin (U. Satzger, diploma thesis, Bielefeld 1991; M. Schleef, K. Werner, U. Satzger, K. Kaupmann and H. Jockusch, In preparation); b: Pfn, gene for profilin (U. Satzger, diploma thesis, Bielefeld 1991). References 1. Ambrose, C., Cheng, S., Fontaine, B., Nadeau, J.H., MacDonald, M., Gusella, J.F. (1992) The alpha subunit of the skeletal muscle sodium channel is encoded proximal to Tk-1 on mouse chromosome 11. Mammalian Genome 3: 151-155. 2. Barton, P., Cohen, A., Robert, B., Fiszman, M.Y., Bonhomme, F., Guenet, J.-L., Leader, D.P., Buckingham, M. (1985) The myosin alkali light chains of mouse ventricular and slow skeletal muscle are indistinguishable and are encoded by the same gene. J. Biol. Chem. 260: 8578-8584. 3. Catterall, W.A. (1988) Structure and function of voltage-sensitive ion channels. Science 242: 50-61. 4. George, A.L. Jr, Ledbetter, D.H., Kallen, R.G., Barchi, R.L. (1991) Assignment of a human skeletal muscle sodium channel alpha-subunit gene (SCN4A) to 17q23.1-25.3. Genomics 9: 555-556. 5. Kallen, R.G., Sheng, Z.-H., Yang, J., Chen, L., Rogart, R.B., Barchi, R.L. (1990) Primary structure and expression of a sodium channel characteristic of denervated and immature rat skeletal muscle. Neuron 4: 233-242. 6. Kaupmann, K., Simon-Chazottes, D., Guenet, J.-L., Jockusch, H. (1992) Wobbler, a mutation affecting motoneuron survival and gonadal functions in the mouse, maps to proximal Chr 11. Genomics 13: 39-43. 7 Malo, D., Schurr, E., Dorfman, J., Canfieid, V., Levenson, R., Gros, P. (1991) Three brain sodium channel alpha-subunit genes are clustered on the proximal segment of mouse chromosome 2. Genomics 10: 666-672. 8. Mandel, G. (1992) Tissue-specific expression of the voltage-sensitive sodium channel. J. Membrane Biol. 125: 193-205. 9. McClatchey, A.J., Van den Berg, P., Pericak-Vance, M.A., Raskind, W., Verellen, C., McKenna-Yasek, D, Rao, K., Haines, J.L., Bird, T., Brown, R.H. Jr, Gusella, Y.F. (1992) Temperature-sensitive mutations in the III-IV cytoplasmic loop region of the skeletal muscle sodium channel gene in paramyotonia congenity. Cell 68: 769-774. 10. Ptacek, L.J., George, A.L. Jr, Griggs, R.C., Tawil, R., Kallen, R.G., Barchi, R.L., Robertson, M., Leppert, M.F. (1991) Identification of a mutation in the gene causing hyperkalemic periodic paralysis. Cell 67: 1021-1027. - Supported by the DFG, SFB 223 - C04 |
