Genetic mapping of the integrin alpha 1 gene (Vla1) to mouse chromosome 13

Polymorphisms and haplotypes of integrinalpha1 (ITGA1) are associated with bone mineral density and fracture risk in postmenopausal Koreans

INTRODUCTION

ITGA1 is involved in the early remodeling of osteoarthritic cartilage and plays an essential role in the regulation of mesenchymal stem cell proliferation and cartilage production. We investigated the association between bone parameters and ITGA1 polymorphisms and their haplotype linkage disequilibrium (LD) blocks (BL_hts). Genetic susceptibility to osteoporosis was studied in 946 postmenopausal Korean women.

METHODS

We identified 67 genetic polymorphisms in ITGA1 region by direct sequencing (n = 114). Eight SNPs were genotyped to further investigate their potential involvement in osteoporosis in postmenopausal women (n = 946). Areal BMD of the lumbar spine and proximal femur was measured using dual-energy X-ray absorptiometry.

RESULTS

The SNPs, +73187C>T (exon 3) and +76969T>G (intron 5), and their BL_hts were associated with bone mineral density (BMD) at various femur sites (p = 0.009-0.05). Moreover, +159174A>C (intron 28) and its haplotype BL3_ht1 showed a highly significant association with risk of non-vertebral fracture (p = 0.002-0.005) and the minor allele of +159174A>C showed a protective effect.

CONCLUSIONS

These results are suggestive of the association of ITGA1 with osteoporosis and related risk in postmenopausal women.

An interstitial telomere array proximal to the distal telomere of mouse chromosome 13

Lambda clones of mouse DNA from BALB/c and C57BL/10, each containing an array of telomere hexamers, were localized by FISH to a region close to the telomere of Chr 13. Amplification of mouse genomic DNA with primers flanking SSRs within the cloned DNA showed several alleles, which were used to type eight sets of RI strains. The two lambda clones contained allelic versions of the interstitial telomere array, Tel-rs4, which is 495 bp in C57BL/10 and which includes a variety of sequence changes from the consensus telomere hexamer. Comparison of the segregation of the amplification products of the SSRs with the segregation of other loci in an interspecies backcross (C57BL/6JEi x SPRET/Ei) F1 x SPRET/Ei shows recombination suppression, possibly associated with ribosomal DNA sequences present on distal Chr 13 in Mus spretus, when compared with recombination in an interstrain backcross, (C57BL/6J x DBA/J) F1 x C57BL/6J, and with the MIT F2 intercross. Analysis of recombination in females using a second interstrain backcross, (ICR/Ha x C57BL/6Ha) F1 x C57BL/6Ha, also indicates recombination suppression when compared with recombination in males of the same strains, using backcross C57BL/6Ha x (ICR/Ha x C57BL/6Ha) F1. Thus, more than one cause may contribute to recombination suppression in this region. The combined order of the loci typed was D13Mit37-D13Mit30-D13Mit148-(D13Rp1, 2, 3, 4, Tel-rs4)-D13Mit53-D13Mit196-D13Mit77-(D13Mit7 8, 35). Data from crosses where apparently normal frequencies of recombination occur suggest that the telomere array is about 6 map units proximal to the most distal loci on Chr 13. This distance is consistent with evidence from markers identified in two YAC clones obtained from the region.

Natural resistance to infection with Legionella pneumophila: chromosomal localization of the Lgn1 susceptibility gene

Legionella pneumophila is a strict intracellular pathogen that replicates in the professional phagocytes of the human and guinea pig host. Although murine macrophages from most inbred strains are non-permissive to intracellular replication of L. pneumophila, inflammatory macrophages from the mouse strain A/J are completely permissive to intracellular replication of this bacterium. This genetic difference is controlled by the expression of a single autosomal gene designated Lgn1, with non-permissiveness behaving as completely dominant over permissiveness. We have used a total of 25 AXB/BXA recombinant inbred mouse strains and 182 (A/J x C57BL/6J) x A/J segregating backcross progeny (A/J, permissive; C57BL/6J, non-permissive) to map the Lgn1 gene. Animals were individually typed for tolerance to intracellular replication by in vitro infection of their inflammatory macrophages with L. pneumophila. All animals segregated into two nonoverlapping groups. Examination of the strain distribution pattern of the AXB/BXA strains for Lgn1 initially identified linkage to Chromosome (Chr) 13 markers. Genotyping of the 25 AXB/BXA strains and the 182 backcross progeny for 11 Chr 13 markers established that Lgn1 mapped to Chr 13, with the gene order and intergene distance D13Mit231-(5.5 +/- 1.5)-D13Mit193-(2.2 +/- 0.9)-D13Mit194- (1.1 +/- 0.6)-D13Mit128-(2.6 +/- 1.0)-Lgn1-(2.2 +/- 0.9)-D13Mit70-(3.9 +/- 1.3)- D13Mit73-(7.2 +/- 1.7)-D13Mit53-(0.7 +/- 0.5)-D13Mit32-(0.7 +/- 0.5)-D13Mit77- (0.7 +/- 0.5)-D13Mit78. This portion of Chr 13 is homologous to the distal portion of human Chr 5, 5q11-5q13, suggesting a possible location of a human LGN1 homolog. Understanding the molecular basis of the high permissiveness of A/J macrophage to L. pneumophila may shed light on the survival strategy of this bacterium in highly permissive human phagocytes. This may be achieved by positional cloning of Lgn1, and the identification of the Lgn1 subchromosomal region reported here is a first step towards that goal.

Molecular markers near two mouse chromosome 13 genes, muted and pearl, which cause platelet storage pool deficiency (SPD)

The recessive muted (mu) and pearl (pe) mutations on Chromosome (Chr) 13 cause pigment dilution and platelet storage pool deficiency (SPD) in mice. In addition, mu causes inner ear abnormalities and pe has symptoms associated with night blindness. Using an interspecific backcross involving the wild-derived Mus musculus musculus (PWK) stock, we have mapped 33 microsatellite markers and four cDNAs relative to mu, pe, and another recessive mutation, satin (sa). Analyzing a total of 528 backcross offspring, we found tight linkage between the pigment loci and several microsatellite markers (D13Mit87, D13Mit88, D13Mit137 with mu; and D13Mit104, D13Mit160, D13Mit161, and D13Mit169 with pe). These markers should aid the eventual molecular identification of these specific SPD genes.