| First Author | Alonso S | Year | 1994 |
| Journal | Mouse Genome | Volume | 92 |
| Issue | 3 | Pages | 508-10 |
| Mgi Jnum | J:20788 | Mgi Id | MGI:68858 |
| Citation | Alonso S, et al. (1994) Genetic map of Igh-C distal region on murine Chromosome 12. Mouse Genome 92(3):508-10 |
| abstractText | Full text of Mouse Genome contribution: Genetic Map Of Igh-C Distal Region On Murine Chromosome 12. Sandrine Alonso, Anne de Meeus, Jacques Demaille and Patrice Bouvagnet. Centre de Recherche de Biochimie Macromoleculaire, CNRS UPR-9008 et INSERM U249, 1919 route de Mende, 34033 Montpellier, FRANCE INTRODUCTION Numerous anonymous markers (3, 4, 10, 12) and genes (1, 7) have been added to the mouse chromosome 12 map since recent reviews of this chromosome were published (2, 5). One of these loci, iv (for situs inversus), has been unambiguously mapped telomeric to Igh-C (3,11), and is the most telomeric known locus on mouse chromosome 12. It lies 12 cM from the Igh-C locus with an inter-marker gap of 11 cM. Here, we present the detailed localisation of 4 markers, Dl2Ler1, Dl2Mit41, Dl2Mit22 and Dl2Nds2, recently assigned to the mouse chromosome 12 subtelomeric region (4, 8). D12Ler1 is a polymorphic locus detected on Southern blots of genomic DNA digested with Taq 1, and hybridized with probe p2F8 (10). D12Mit41, D12Mit22 and D12Nds2 are microsatellites (4, Research Genetics, Huntsville, AL). Length variations of the microsatellite sequences were detected by polymerase chain reaction (PCR) using a radiolabeled primer, as previously described (4). RESULTS In a previous experiment, aimed at mapping the iv locus (3), we bred a total of 242 backcross animals homozygous for the iv allele. 127 of these mice were born from the interspecific backcross [(Sl/Col x Mus spretus) F1 x Sl/Col] and 115 from the intersubspecific backcross [(Sl/Col x Mus musculus musculus) F1 x Sl/Col]. Studying the genetic constitution of these backcross mice, we found that 105 animals of the first backcross and 108 of the second were homozygous along the D-12Mit6-Igh-iv interval. We initially typed parental mice with these new markers. No polymorphism at D12Mit41 locus was detected between musculus and Sl/Col alleles. For the D12Ler1 locus, probe p2F8 revealed bands on musculus mice which could not be distinguished unambiguously from Sl/Col bands, precluding further analysis. Nevertheless, we obtained 4 spretus specific fragments (figure 1). D12Nds2 and D12Mit22 polymorphisms were detected as previously described (4). Figure 1 Legend: Examples of RFLP associated with the p2F8 probe. Ten ug of genomic DNA from Sl/Col (Sl/Sl), Fl hybrid (Sp/Sl) and 5 back-cross mice were digested with Taql and analyzed by Southern blot with the probe p2F8. The Sl/Col (bands 1 and 2) and spretus (bands 3, 4, 5 and 6) specific bands are detected. In order to confirm that these 4 markers map to the distal region of chromosome 12, we selected 22 mice of each experimental cross which were homozygous for the Sl/Col allele from D12Mit6 to iv (3). All mice were homozygous at D12Mit41 and Dl2Nds2 loci, giving strong evidence that they actually map to this region. The 4 spretus specific fragments, revealed by probe p2F8, form 3 groups of segregation, corresponding to 3 loci: bands 3 and 5 (respectively 3.4 and 2.5 kb) which always co- segregate, band 4 (2.8 kb) and band 6 (2.3 kb). Bands 3-5 and 4 are detected in 8 and 3 out of 22 backcross mice, respectively. In contrast, none of the backcross mice homozygous for the Sl/Col allele present band 6. Therefore, we concluded that band 6 maps to chromosome 12 sub-telomere. According to a previous work, band 4 is the chromosome 10 locus: D10Ler2 (10). Bands 3-5 correspond to a third locus previously undescribed. These 2 last bands are fainter and may be undetected on a short exposure time. Ten out of 22 spretus backcross mice and 11 out of 22 musculus backcross mice were however heterozygous at the D12Mit22 locus. This observation excludes Dl 2Mit22 from the distal region of chromosome 12. Twenty two spretus and 7 musculus backcross mice with a recombination between Igh-C and iv were then tested with probe p2F8, and micro-satellites Dl 2Mit41 and Dl 2Nds2. The different haplotypes are shown in Figure 2. Dl2Nds2 cosegregates with Dl2Mit8 in each mouse in this panel, placing it between (lgh-C, Ckb) and Crip. D12Mit41 and D12Ler1 map between Crip and iv, with D12Ler1 more distal than Dl2Mit41. We assumed that the 83 [(Sl/Col x Mus spretus) F1 x Sl/Col] and the 86 [(Sl/Col x Mus musculus musculus) F1 x Sl/Col] backcross mice homozygous for the Sl/Col genome between Dl2Mit6 and iv loci were also homozygous at the Dl2Ler1, Dl2Mit41, and Dl2Nds2 loci. The LINKAGE program package (9) was used to evaluate the genetic distances. The 7 markers (lgh-C, D12Mit8, Crip, Dl2Nds2, Dl2Mit41, Dl2Ler1 and iv) were simultaneously positioned using a multipoint program analysis (Xilink). This program gave the same order of loci with spretus and musculus crosses. With pooled data, the genetic order and distances are: centromere - (Igh-C, Ckb) - 0.1 cM (0 - 0.1) - (D12Mit8, D12Nds2) - 0.5 CM (0.2 - 1.1) - Crip - 3.2 cM (1.8 - 3.7) - D12Mit41 - 5.8 cM (5.3 - 7.4) - D12Ler1 - 4.9 cM (3 - 5.5) - iv - telomere, as shown in Figure 3A, with approximate confidence limits of 1 Ð unit of Lod score. Odds against inversion of adjacent loci are highly significant except for Dl2Nds2 and Dl2Mit8 where there is no recombination event between the markers (Figure 3B). Figure 2 Legend: Haplotype analysis of 22 [(Sl/Col x Mus spretus) F1 x Sl/Col] and 7 [(Sl/Col x Mus musculus musculus) F1 x Sl/Col] backcross mice, selected as having a recombination event between the Igh-C and iv loci. Typed loci are on the left. The number of progeny presenting a particular haploytype is shown at the top. Filled boxes represent the Sl/Col alleles, and open boxes represent the spretus or musculus alleles. Figure 3 Legend: A) Genetic map of markers within the subtelomeric murine chromosome 12 region, constructed with the Xilink program. Filled areas represent approximate confidence limits (1-lod-unit-decrease in likelihood). B) Odds against inversion of adjacent loci are indicated by brackets. 1=iv, 2=Dl2Lerl, 3=Dl2Mit41, 4=Crip, 5=D12Nds2, 6=D12Mit8, 7=Igh-C, Ckb. CONCLUSION In conclusion, this study extends the chromosome 12 map (6) toward the telomere, with a maximum inter-marker distance of only 5.8 cM between D12Ler1 and D12Mit41 loci. iv localizes 14.4 cM telomeric to D12Nds2. Finally, it seems that D12Mit22 was wrongly assigned to chromosome 12 distal region. ACKNOWLEDGMENTS We are indebted to M. Lathrop for introducing us to the LINKAGE programs. Dr. E. Birkenmeier, Pr. J.L. Guenet and H. Le Roy are thanked for sending us probes. Support for S. Alonso and A. de Meeus was provided by Ph. D. stipends from the Ministere de la Recherche et de la Technologie. 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