| First Author | Davisson MT | Year | 1992 |
| Journal | Mouse Genome | Volume | 90 |
| Pages | 218-19 | Mgi Jnum | J:18388 |
| Mgi Id | MGI:66377 | Citation | Davisson MT, et al. (1992) Maps of centromere ends of Chromosomes. Mouse Genome 90:218-19 |
| abstractText | Full text of Mouse Genome Contribution: Maps of centromere ends of Chromosomes. Muriel T. Davisson and Ellen C. Akeson; The Jackson Laboratory, Bar Harbor, Maine 04609 USA. Determining the ends of chromosomal maps accurately has been difficult because, until very recently, the only markers for chromosome ends have been chromosomal aberrations. In the present composite map (GBASE, 1992), the centromere ends of ten chromosomes (Chrs 3, 4, 5, 6, 8, 9, 10, 11, 15, and 19) have been mapped using Robertsonian chromosomes. Many Robertsonian chromosomes are known to suppress recombination in the pericentromeric regions of the chromosomes involved (Cattanach, 1978; Davisson and Akeson, submitted). We have confirmed that recombination suppression is not common to all murine Robertsonians, since none of the three Robertsonians involving Chr 7 that we tested suppressed recombination in Chr 7. Because we can not predict which Robertsonian chromosomes will suppress recombination and to what extent, the centromere-to-first-locus distances displayed on the map are likely to be underestimated. A further complication is that for some chromosomes this distance has been determined using loci more distal than the most proximal locus on the chromosome. In all Robertsonians we have studied, the suppression does not extend more than 15-20 cM distal to the centromere, thus it is clear from our data and that of others (summarized in Davisson and Akeson, submitted) that the extent of suppression can vary for different Robertsonian chromosomes even when they suppress recombination. Here we review the literature for centromere mapping for all chromosomes and assess the accuracy of the estimates. The only chromosomes in which the distance from the centromere end to the most proximal marker is well established are Chrs 7, 14, and 17 based on ovarian teratoma data (Eppig and Eicher, 1983, 1988; Artzt et al., 1987). Two additional chromosomes have reasonably good estimates for the centromere end. For Chr 12 the centromere-to-first-locus distance has been established using Rb(12.14)8Rma (Davisson et al., 1991) and a ribosomal RNA region locus Rnr12 . There is no evidence for suppression because distances among proximal markers appear to be same when either marker is present. In Chr 13 the centromere-to-first-locus distance has been established using a reciprocal translocation T(10;13)199H, in which the Chr 13 breakpoint is in the centromeric heterochromatin and which shows 17% recombination with beige (bg) (Lyon and Glenister, 1974). Although some reciprocal translocations may inhibit recombination, in general those that do, do not have as severe an effect as do Robertsonian chromosomes (Searle, 1989). C-bands (pericentromeric heterochromatin) are also useful markers for the centromere when polymorphisms exist, although they are more time-consuming to score in crosses (Akeson and Davisson, 1991). C-band markers may also affect recombination although probably to a lesser degree than Robertsonian chromosomes. Heterochromatin polymorphisms have been used to map the centromere ends of Chrs 1, 2, 16, 18, and X (Davisson and Akeson, submitted; Davisson, 1985; Lane et al., 1981; Eicher et al., 1977) and the centromere-to-first-locus distance for these four chromosomes are probably reasonably good. It should be noted that the Chr 18 heterochromatin marker (Dp(Hcl8); Lane et al., 1981) and, probably, the Chr 2 heterochromatin marker (Hc2l; Davisson and Akeson, in press) we used are duplications of the heterochromatic material and are more likely to interfere with pairing and recombination than other C-band variants. In synaptonemal complex preparations from male mice heterozygous for Hc2l however, we were unable to detect pairing delay in any of the bivalents, suggesting the extra large heterochromatin block does not interfere with meiotic pairing and, therefore, with recombination estimates. The correlation between genetic recombination suppression and delayed chromosomal pairing is supported by the results of our work in which seven of the ten Robertsonians we studied showed pairing delay in the centromeric region and suppressed recombination; the remaining three Robertsonians showed very little pairing delay and did not alter genetic recombination. Although there is no evidence to rule out that distances determined with heterochromatin polymorphisms also may be underestimates, our data indicate that such polymorphisms do not suppress recombination as much as Robertsonian chromosomes do. For the ten remaining chromosomes (Chrs 3, 4, 5, 6, 8, 9, 10, 11, 15, and 19) the distances from the centromeres to first markers have only been determined using Robertsonian chromosomes (GBASE, 1992) and users of the mouse map should be aware that the estimated distance may be inaccurate. Acknowledgements This work was supported by National Institutes of Health grant RR01183 and National Science Foundation grant DIR89-15728. The Jackson Laboratory is fully accredited by the American Association for the Accreditation of Laboratory Animal Care. References Akeson EC, Davisson MT. 1991. C-band polymorphisms in exotic inbred strains of mice: a method for mapping centromere ends of chromosomes. Cytogenet Cell Genet 57:217-220. Artzt K, Calo C, Neuner Pinheiro E, Dimeo-Talento A, Tyson FL. 1987. Ovarian teratocarcinomas in LT/Sv mice carrying t-mutations. Dev Genet 8:l-9. Cattanach BM. 1978. Crossover supression in mice heterozygous for tobacco mouse metacentrics. Cytogenet Cell Genet 20:264-281. Davisson MT. 1985. Rb(16.17)7Bnr inhibits genetic recombination. Mouse News Letter 73:19. Davisson MT, Akeson EC. Recombination suppression by heterozygous Robertsonian chromosomes in the mouse. Genetics, submitted. Davisson MT, Guay-Woodford LM, Harris HW, D'Eustachio P. 1991. The mouse polycystic kidney disease mutation (cpk) is located on proximal chromosome 12. Genomics 9:778-781. Eicher EM, May J, Southard JL, Washburn L. 1977. [Location of spf relative to centromere on X Chromosome.] Mouse News Lett 56:42. Eppig JT, Eicher EM. 1983. Application of the ovarian teratoma mapping method in the mouse. Genetics 103:797-812. Eppig JT, Eicher EM. 1988. Analysis of recombination in the centromere region of mouse Chromosome 7 using ovarian teratoma and backcross methods. J Hered 79:425-429. GBASE. 1992. The on-line genomic database of the mouse maintained at The Jackson Laboratory by DP Doolittle, AL Hillyard, LJ Maltais, MT Davisson, JN Guidi, and TH Roderick. Lane PW, Searle AG, Beechey CV, Eicher EM. 1981. Chromosome 18 of the house mouse. J Hered 72: 409-412. Lyon MF, Glenister PH. 1974. Position of translocation break in T(10;13)199H. Mouse News Lett 51: 21-22. Searle AG, 1989. Chromosomal variants, pp. 582-631. In: Lyon MF and Searle AG (eds.), Genetic Variants and Strains of the Laboratory Mouse. Second Edition. Oxford University Press, Oxford. |
