Ota N, Nakajima T, Nakazawa I, Suzuki T, Hosoi T, Orimo H, Inoue S, Shirai Y, Emi M
Department of Molecular Biology, Nippon Medical School, Kawasaki, Japan.
J Hum Genet. 2001;46(5):267-72. doi: 10.1007/s100380170077.
Interleukin-6 (IL6) has come to be regarded as a potential osteoporotic factor because it has stimulatory effects on cells of the osteoclast lineage, and, thus, may play a role in the pathogenesis of bone loss associated with estrogen deficiency. We previously described association of the IL6 microsatellite with bone mineral density (BMD), as well as genetic linkage of the IL6 locus to human osteoporosis, by means of sib-pair analysis. However, the molecular mechanism by which this locus regulates BMD remains unknown. Accordingly, we searched for polymorphisms in the 5' and 3' flanking regions and in all five exons of the IL6 gene in a Japanese population sample. We identified three single-nucleotide sequence variations: a C/G substitution at nucleotide (nt) -634 in the promoter region, a G/A substitution at nt 4391 in the 3' noncoding region, and a variation in the AnTn tract around nt -447. The last of these had already been observed in Caucasians, as well as in Japanese. The single-nucleotide polymorphism at -634 created a restriction site for the BsrBI endonuclease, and the frequency of the minor (G) allele was 0.184. Five haplotypes were constructed among three variations examined in the population. Linkage disequilibrium was observed between the variation at -634 and the variation at 4391, as well as between the variation at -634 and the AnTn tract variation. We found a significant correlation, in 470 subjects, between the presence of the G allele and decreased BMD, by analysis of variance. When BMD values were compared among the three genotypic groups (G/G, G/C, C/C) at nt -634, BMD was lowest among the G/G homozygotes (mean +/- SD; 0.284 +/- 0.062g/cm2), highest among the C/C homozygotes (0.314 +/- 0.059g/cm2), and intermediate among the heterozygotes (0.303 +/- 0.066g/cm2; P < 0.05). Given the several lines of evidence from different genetic studies, we suggest that IL6 is, indeed, one of the genes affecting bone metabolism, in which variations can lead to osteoporosis.
白细胞介素-6（IL6）已被视为一种潜在的骨质疏松因素，因为它对破骨细胞谱系的细胞具有刺激作用，因此可能在与雌激素缺乏相关的骨质流失发病机制中发挥作用。我们之前通过同胞对分析描述了IL6微卫星与骨密度（BMD）的关联，以及IL6基因座与人类骨质疏松症的遗传连锁。然而，该基因座调节骨密度的分子机制仍不清楚。因此，我们在一个日本人群样本中搜索了IL6基因5'和3'侧翼区域以及所有五个外显子中的多态性。我们鉴定出三个单核苷酸序列变异：启动子区域核苷酸（nt）-634处的C/G替换、3'非编码区域nt 4391处的G/A替换以及nt -447周围AnTn序列的变异。其中最后一个变异在白种人和日本人中均已被观察到。-634处的单核苷酸多态性产生了BsrBI内切酶的限制性位点，次要（G）等位基因的频率为0.184。在人群中检测的三个变异之间构建了五种单倍型。在-634处的变异与4391处的变异之间以及-634处的变异与AnTn序列变异之间观察到连锁不平衡。通过方差分析，我们在470名受试者中发现G等位基因的存在与骨密度降低之间存在显著相关性。当比较nt -634处三个基因型组（G/G、G/C、C/C）的骨密度值时，G/G纯合子中的骨密度最低（平均值±标准差；0.284±0.062g/cm2），C/C纯合子中的骨密度最高（0.314±0.059g/cm2），杂合子中的骨密度处于中间水平（0.303±0.066g/cm2；P<0.05）。鉴于来自不同遗传研究的多条证据，我们认为IL6确实是影响骨代谢的基因之一，其变异可导致骨质疏松症。
