Nobutaka Ota

A nucleotide variant in the promoter region of the interleukin-6 gene associated with decreased bone mineral density

AbstractInterleukin-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 ± 0.062 g/cm2), highest among the C/C homozygotes (0.314 ± 0.059 g/cm2), and intermediate among the heterozygotes (0.303 ± 0.066 g/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.

Allelic variants in the interleukin-6 gene and essential hypertension in Japanese women.

Genes that can be implicated in hypertension in experimental animals are plausible candidates in the pathogenesis of human hypertension. A recent genome-wide search for quantitative-trait loci (QTL) in hypertensive rats revealed a strong correlation between the interleukin-6 (IL-6) locus on rat chromosome 4 and systolic, diastolic, and mean arterial pressure in this mammalian species. To investigate a possible association between genetic variations of the IL-6 gene and hypertension in humans, we identified two novel single-nucleotide sequence variations, a C/G substitution at −634 in the promoter region and a G/A substitution at 4391 in a 3 ′ non-coding portion of exon 5, and a previous reported sequence variant, an A/T variation in the composition of the AnTn tract around −447 in the promoter region ( Fishman D et al. J Clin Invest 1998; 102: 1369–1376 ), within a test population of 96 Japanese subjects. Allelic associations involving these variations were analyzed in 150 hypertensive and 143 normotensive Japanese women. The distribution of alleles of the three polymorphisms, as well as a dinucleotide repeat present at the IL-6 locus, was similar in the two groups. Therefore, the IL-6 gene appears to play a minimal role in the genetic etiology of essential hypertension in Japanese women.

Association of Bone Mineral Density with Polymorphism of the Human Calcium-Sensing Receptor Locus

Abstract. A strong correlation between bone mass and genetic factors has been shown in twins and family studies. Some of the genes involved would regulate bone metabolism, bone formation, and resorption, all processes that determine bone mass. One candidate genes, calcium-sensing receptor (CASR) in the parathyroid gland, regulates calcium homeostasis by sensing decreases in extracellular calcium level and effecting an increase in secretion of parathyroid hormone (PTH) and calcium (Ca) reabsorption in the kidney. We have investigated a possible association between the CA-repeat polymorphism at the human CASR gene locus and the bone mineral density (BMD) of radial bone in 472 postmenopausal Japanese women. Genotypes were classified into nine groups according to the number of CA repeats present, from 20 to 12. BMD was expressed as the adjusted BMD, which was the body mass index (BMI), and age-adjusted average BMD. The 247 women who had an A3 allele (228 bp, containing 18 repeats of CA) had significantly lower adjusted BMD (mean ± SD: 0.303 ± 0.059 versus 0.316 ± 0.063 g/cm2; P= 0.0308) than the participants (n = 201) who did not carry an allele of that size. This result suggests that genetic variation at the CASR gene locus is associated with some determinants for BMD in postmenopausal women.

Ethnic Difference in Contribution of Sp1 Site Variation of COLIA1 Gene in Genetic Predisposition to Osteoporosis

Abstract. Osteoporosis, a condition characterized by low bone mineral density (BMD) leading to bone fragility [1], is a major public health concern in Japan as well as in other countries. Although genetic predisposition seems to be a factor in the pathogenesis of osteoporosis [2–4], the precise cohort of genes that may be involved is not well defined. The COLIA1 and COLIA2 genes encode polypeptide constituents of collagen type Iα1 and Iα2, respectively. Both are important candidates as genetic regulators of BMD, since mutations in either gene result in osteogenesis imperfecta, a disorder characterized by severe osteoporosis [5]. Some patients with adult osteoporosis also carry mutations in COLIA1 or COLIA2 genes [6].

Linkage of human tumor necrosis factor-alpha to human osteoporosis by sib-pair analysis

Osteoporosis as well as osteopenia are common human conditions considered to result from the interplay of multiple genetic and environmental factors. Twin and family studies have yielded strong correlation between measures of bone mass and a number of genetic factors. Certain genes (eg, cytokines such as interleukin-1, interleukin-6, or tumor necrosis factor-alpha) are capable of regulating metabolism, formation, and resorption of bone; all processes that determine bone mass. We tested 192 sib-pairs of adult Japanese women from 136 families for genetic linkage between osteoporosis and osteopenia phenotypes and allelic variants at the tumor necrosis factor-alpha (TNFA) locus, using a dinucleotide-repeat polymorphism located near the gene. The TNFA locus showed evidence for linkage to osteoporosis, with mean allele sharing of 0.478 (P = 0.30) in discordant pairs and 0.637 (P = 0.001) in concordant affected pairs. Linkage with osteopenia was also significant in concordant affected pairs (P = 0.017). Analyses limited to the post-menopausal women in our cohort showed similar or even stronger linkage for both phenotypes. The results provide evidence that genetic variations within the TNFA locus or adjacent genes affect regulation of mineral metabolism in bone and some of them confer risk for osteoporosis in adult women.

A common Ile796Val polymorphism of the human SREBP cleavage-activating protein (SCAP) gene.

AbstractWe identified a new common amino acid polymorphism of isoleucine/valine at codon 796 in exon 16 of the gene for human sterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP), a central regulator of lipid synthesis and metabolism in animal cells. It can be detected as an MslI restriction fragment length polymorphism. The allelic frequencies were: isoleucine (A) allele, 0.57 and valine (G) allele, 0.43. This polymorphism may be useful for genetic studies of disorders affecting intracellular lipid metabolism and hyperlipidemia.

ISOLATION AND RADIATION HYBRID MAPPING OF A HIGHLY POLYMORPHIC CA REPEAT SEQUENCE AT THE HUMAN NUCLEAR FACTOR KAPPA-BETA SUBUNIT 1 (NFKB1) LOCUS

AbstractThe transcriptional factor nuclear factor kappa-beta (NFKB) consists of a multicomponent protein complex that plays a major role in the regulation of many viral and cellular genes. The NFKB complex has two alternative DNA binding subunits. We isolated a polymorphic dinucleotide (CA) repeat sequence from a genomic clone containing the NFKB subunit 1 (NFKB1) gene located at 4q23-24. High heterozygosity (0.813) makes this polymorphism a useful marker in the genetic study of disorders affecting the immune response and cell differentiation.

Five novel single-nucleotide polymorphisms of human interferon gamma identified by sequencing the entire gene

AbstractInterferon gamma (IFNG) plays important roles in the regulation of bone remodelling. We describe here six single-nucleotide polymorphisms (SNPs) in the IFNG gene, five of which are novel, and their allelic frequencies in the Japanese population, as determined by sequencing 48 alleles of the entire gene. Four of these polymorphisms were identified inside the third intron, at nucleotide (nt) positions 2459 (A/G), 2671 (T/C), 3177 (T/G), and 3273 (G/A). In exon 4, SNPs were identified at nt positions 5199 (A/T) and 5272 (A/G). These polymorphic sites will be useful for genetic studies of disorders that affect the inflammatory process or calcium metabolism.

Isolation and radiation hybrid mapping of a highly polymorphic CA repeat sequence at the SREBP cleavage-activating protein (SCAP) locus

AbstractSterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP) is a central regulator of lipid synthesis and uptake in animal cells. A polymorphic dinucleotide (CA) repeat sequence was isolated from a genomic clone containing the SCAP gene and was mapped to chromosome 3p21.3. High heterozygosity (0.89) makes this polymorphism a useful marker in the genetic study of disorders affecting lipid metabolism.

Novel single nucleotide polymorphisms of the human colony-stimulating factor 2 (CSF2) gene identified by sequencing the entire gene

AbstractWe describe three single nucleotide polymorphisms (SNPs) of the human colony-stimulating factor 2 (CSF2) gene and their allelic frequencies, as determined by direct sequencing of 48 alleles of the entire CSF2 gene. Three polymorphisms were identified, at nucleotide positions 1816 (T/C), 2284 (C/T), and 3079 (G/A). These polymorphisms will be useful in genetic studies not only of hematologic disorders but also of disorders of bone metabolism.