- Email: [email protected]
The genetics of osteoporosis
Bone Vol. 25, No. 1 July 1999:85– 86
The Genetics of Osteoporosis S. H. RALSTON Department of Medicine and Therapeutics, University of Aberdeen, Aberdeen, Scotland, UK
Importance of Genetics in Osteoporosis
Candidate Genes for Regulation of Bone Mass
Genetic factors play an important role in the pathogenesis of osteoporosis. Studies in twins and in normal families indicate that between 75% and 85% of the variance in bone mineral density (BMD) is under genetic control,22 and other markers of osteoporotic fracture risk such as ultrasound attenuation and bone turnover also appear to be genetically determined.2,14 This indicates that the effects of heredity on osteoporotic fracture risk extend beyond those on bone mass alone, which is consistent with the clinical observation that a family history of hip fracture predicts osteoporotic fracture independently from bone mass. The molecular-genetic basis by which bone mass and other aspects of fracture risk is determined remains poorly understood, but it is thought that many genes, each with small effects, may be responsible, rather than a small number of genes with large effects.10
The vitamin D receptor gene (VDR) is the most widely studied candidate gene. Three common single-nucleotide polymorphisms (SNP) have been described in the 39 region of VDR, recognized by the enzymes BsmI, ApaI, and TaqI. These polymorphisms have been associated with bone density in some populations, but not in others.4 Environmental factors such as calcium and vitamin D intake can modify the effects of VDR alleles on calcium metabolism, and it has been suggested that the relationship between VDR genotype and bone mass may be masked in populations with a high calcium intake.19 Another SNP has been described in exon 2 of VDR, recognized by the enzyme FokI. This SNP generates an alternative translation start site, resulting in production of a variant protein.1 The exon 2 polymorphism has been associated with bone mass and bone loss in some populations, but in others, no effect has been found.6,9 Polymorphisms of several other candidate genes such as interleukin-6 (IL-6),18 transforming factor-beta (TGF-b),16,26 the oestrogen receptor-alpha (ERa) gene,15 the calcitonin receptor gene,17 the apolipoprotein E gene (APOE),21 and the osteocalcin gene5 have also been associated with bone mass and/or osteoporotic fracture in various studies. A variable number tandem repeat polymorphism in the IL-6 gene was associated with peak bone mass in one population,18 but this has not yet been studied in other populations. An intronic polymorphism of the TGF-b gene has recently been found to be associated with very low bone mass and osteoporotic fracture in a Danish population,16 and a another group has identified a coding polymorphism that is related to bone mass and osteoporotic fracture in a Japanese population.26 The coding polymorphism is of interest in that it seems to influence serum levels of TGF-b. A coding polymorphism that affects the calcitonin receptor gene has been described that is associated with bone mass in Italian women. The relationship between this polymorphism and bone density in other populations remains to be described. Polymorphisms of the APOE gene have also been associated with bone mass.21 Although the mechanism responsible for this association remains unclear, it has been speculated to involve an alteration in transport of the fat soluble vitamin K, which is necessary for carboxylation of osteocalcin, an osteoblast-specific protein. A polymorphism has been identified in the promoter region of the osteocalcin gene which has been found to relate to bone mass in a Japanese study,5 although this has not been investigated in other populations. Polymorphisms of the ERa gene have been fairly extensively studied in relation to bone mass.19 Two common polymorphisms have been described in the first intron of the ER gene, recognized by the enzymes PvuII and XbaI, and these are in linkage disequilibrium with another TA repeat polymorphism in the promoter. In some populations, ER PvuII and XbaI genotypes
Ways of Identifying Genes That Regulate Bone Mass Linkage analysis provides an efficient way to identify disease genes in simple Mendelian disorders, and a family has recently been identified where high bone mass (Z-score . 13.0) was inherited as an autosomal dominant trait over several generations. A genome search using classical linkage techniques in this family showed the presence of a candidate locus on chromosome 11q12-13,13 although the gene responsible remains to be defined. Similar studies have been conducted in families where low bone mass was inherited in an autosomal dominant fashion. In these studies, nonparametric analysis showed evidence of linkage to a locus on chromosome 1p36 and possible evidence of linkage to two other loci on chromosomes 2p23 and 4qter. Analysis of allele sharing in sibling pairs on a genome-wide basis provides an alternative approach to defining disease genes and has the advantage that no assumptions need be made as to the mode of inheritance. Genome-wide searches for candidate loci that determine bone mass are currently underway in humans, but the results of these studies have not yet been reported. Genetic mapping studies in experimental animals provide a further approach to identify the genes responsible for regulation of bone mass. Although these studies are underway, the results have not yet been published. The candidate gene approach provides a fourth way to define the genetic basis of complex diseases, and this has been extensively studied in the osteoporosis field as summarized below.
Address for correspondence and reprints: Stuart H. Ralston, M.D., F.R.C.P., Department of Medicine and Therapeutics, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland. E-mail: [email protected] © 1999 by Elsevier Science Inc. All rights reserved.
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8756-3282/99/$20.00 PII S8756-3282(99)00115-5
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S. H. Ralston Genetics of osteoporosis
have been significantly associated with bone mass in some populations,15,24 whereas in others, no effect has been found.11 The polymorphic TA repeat polymorphism has been associated with bone mass in one study,20 but this result has not yet been confirmed in other populations. The mechanisms by which these polymorphisms associate with bone mass are unclear. Although it is unlikely that the intronic polymorphisms have functional effects, the TA polymorphism could play a role in gene regulation. The collagen type I genes are further candidates for genetic regulation of bone mass since mutations in the protein coding regions of these genes give rise to a severe osteoporotic phenotype in the form of osteogenesis imperfecta. Although the collagen protein chains have been found to be normal in most osteoporotic patients, a polymorphism has recently been identified in a regulatory region of the COLIA1 gene which is more common in osteoporotic patients than in normal individuals.8 This polymorphism is situated at a binding site for the transcription factor Sp1 in the first intron of COLIA1, and has been found to be associated with bone mass and osteoporotic fracture in several Caucasian populations.7,8,23 This polymorphism is of interest since the association with fracture is much stronger than can be explained by genotype specific differences in bone mass. This raises the possibility that COLIA1 alleles may predispose to fracture by affecting other determinants of fracture risk such as bone quality or skeletal geometry. In this regard, preliminary data suggest that the polymorphism alters the affinity of Sp1 binding to DNA, transcription of the COLIA1 gene, and the production of the collagen aI protein chain. It is of interest that the COLIA1 polymorphism seems to be absent from Asian and African populations, which have low rates of osteoporotic fracture.3 Since segregation analysis suggests that several genes may combined to regulate bone mass, clinical studies have also looked at the possibility that genetic polymorphisms may interact to predict bone mass. Most work in this area has focused on the VDR and ERa genes, where combining information from SNPs in both genes has been found to identify subgroups of individuals with low and high bone mass.12,25 Clinical Applications for Genetic Studies Studies on the genetic basis of osteoporosis are in their infancy and much further work needs to be done to discover other genes that regulate bone mass and the mechanisms by which they do so. The results of these studies have clinical relevance, not only in identifying informative polymorphisms, which could be of value in the assessment of osteoporotic fracture risk, and predicting response to treatment, but also in uncovering new molecular targets for therapeutic intervention in the prevention and treatment of osteoporosis. References 1. Arai, H., Miyamoto, K.-I., Taketani, Y., et al. A vitamin D receptor gene polymorphism in the translation initiation codon: Effect on protein activity and relation to bone mineral density in Japanese women. J Bone Miner Res 12:915–921; 1997. 2. Arden, N. K., Baker, J., Hogg, C., Baan, K., and Spector, T. D. The heritability of bone mineral density, ultrasound of the calcaneus and hip axis length: a study of postmenopausal twins. J Bone Miner Res 11:530 –534; 1996. 3. Beavan, S., Prentice, A., Dibba, B., Yan, L., Cooper, C., and Ralston, S. H. Polymorphism of the collagen type I alpha 1 gene and ethnic differences in hip-fracture rates. N Engl J Med 339:351–352; 1998. 4. Cooper, G. S. and Umbach, D. M. Are vitamin D receptor polymorphisms associated with bone mineral density? A meta-analysis. J Bone Miner Res 11:1841–1849; 1996.
Bone Vol. 25, No. 1 July 1999:85– 86 5. Dohi, Y., Masayuki, I., Ohgushi, H., et al. A novel polymorphism in the promoter region for the human osteocalcin gene: the possibility of a correlation with bone mineral density in postmenopausal Japanese women. J Bone Miner Res 13:1633–1639; 1998. 6. Eccleshall, T. R., Garnero, P., Gross, C., Delmas, P. D., and Feldman, D. Lack of correlation between start codon polymorphism of the vitamin D receptor gene and bone mineral density in premenopausal French women: the OFELY study. J Bone Miner Res 13:31–35; 1998. 7. Garnero, P., Borel, O., Grant, S. F. A., Ralston, S. H., and Delmas, P. D. Collagen I a 1 polymorphism, Bone Mass and Bone Turnover in Healthy French Pre-Menopausal Women: The OFELY study. J Bone Miner Res 13:813– 818; 1998. 8. Grant, S. F. A., Reid, D. M., Blake, G., Herd, R., Fogelman, I., and Ralston, S. H. Reduced bone density and osteoporosis associated with a polymorphic Sp1 site in the collagen type I alpha 1 gene. Nature Genetics 14:203–205; 1996. 9. Gross, C., Eccleshall, T. R., Malloy, P. J., Villa, M. L., Marcus, R., and Feldman, D. The presence of a polymorphism at the translation initiation site of the vitamin D receptor gene is associated with low bone mineral density in postmenopausal Mexican-American women. J Bone Miner Res 12:1850 –1856; 1997. 10. Gueguen, R., Jouanny, P., Guillemin, F., Kuntz, C., Pourel, J., and Siest, G. Segregation analysis and variance components analysis of bone mineral density in healthy families. J Bone Miner Res 12:2017–2022; 1995. 11. Han, K. O., Moon, I. G., Kang, Y. S., Chung, H. Y., Min, H. K., and Han, I. K. Nonassociation of estrogen receptor genotypes with bone mineral density and estrogen responsiveness to hormone replacement therapy in Korean postmenopausal women [see comments]. J Clin Endocrinol Metab 82:991–995; 1997. 12. Gennari, L., Becherini, L., Masi, L., Mansani, R., Gonnelli, S., Cepollaro, C., Martini, S., Montagnani, A., Lentini, G., Becorpi, A. M., and Brandi, M. L. Vitamin D and estrogen receptor allelic variants in Italian postmenopausal women: evidence of multiple gene contribution to bone mineral density. J Clin Endocrinol Metab 83:939 –944; 1998. 13. Johnson, M. L., Gong, G., Kimberling, W., Recker, S., Kimmel, D. B., and Recker, R. R. Linkage of a gene causing high bone mass to human chromosome 11 (11q12-13). Am J Hum Genet 60:1326 –1332; 1997. 14. Kelly, P. J., Hopper, J. L., Macaskill, G. T., Pocock, N. A., Sambrook, P. N., and Eisman, J. A. Genetic factors in bone turnover. J Clin Endocrinol Metab 72:808 – 813; 1991. 15. Kobayashi, S., Inoue, S., Hosoi, T., Ouchi, Y., Shiraki, M., and Orimo, H. Association of bone mineral density with polymorphism of the estrogen receptor gene. J Bone Miner Res 11:306 –311; 1996. 16. Langdahl, B. L., Knudsen, J. Y., Jensen, H. K., Gregersen, N., and Eriksen, E. F. A sequence variation: 713-8delC in the transforming growth factor-beta 1 gene has higher prevalence in osteoporotic women than in normal women and is associated with very low bone mass in osteoporotic women and increased bone turnover in both osteoporotic and normal women. Bone 20:289 –294; 1997. 17. Masi, L., Becherini, L., Colli, E., et al. Polymorphisms of the calcitonin receptor gene are associated with bone mineral density in postmenopausal Italian women. Biochem Biophys Res Commun 248:190 –195; 1998. 18. Murray, R. E., McGuigan, F., Grant, S. F. A., Reid, D. M., and Ralston, S. H. Polymorphisms of the interleukin-6 gene are associated with bone mineral density. Bone 21:89 –92; 1997. 19. Ralston, S. H. The genetics of osteoporosis. Q J Med 90:247–251; 1997. 20. Sano, M., Inoue, S., Hosoi, T., et al. Association of estrogen receptor dinucleotide repeat polymorphism with osteoporosis. Biochem Biophys Res Commun 217:378 –383; 1995. 21. Shiraki, M., Shiraki, Y., Aoki, C., et al. Association of bone mineral density with apoplipoprotein E phenotype. J Bone Miner Res 12:1438 –1445; 1997. 22. Soroko, S. B., Barret-Connor, E., Edelstein, S. L., and Kritz-Silverstein, D. Family history of osteoporosis and bone mineral density at the axial skeleton: The Rancho Bernardo study. J Bone Miner Res 9:761–769; 1994. 23. Uitterlinden, A. G., Burger, H., Huang, Q., et al. Relation of alleles of the collagen type I a 1 gene to bone density and risk of osteoporotic fractures in postmenopausal women. N Engl J Med 338:1016 –1022; 1998. 24. Willing, M., Sowers, M., Aron, D., et al. Bone mineral density and its change in white women: estrogen and vitamin D receptor genotypes and their interaction. J Bone Miner Res 13:695–705; 1998. 25. Willing, M., Sowers, M., Aron, D., et al. Bone mineral density and its change in white women: estrogen and vitamin D receptor genotypes and their interaction. J Bone Miner Res 13:695–705; 1998. 26. Yamada, Y., Miyauchi, A., Goto, J., et al. Association of a polymorphism of the transforming growth factor-betal gene with genetic susceptibility to osteoporosis in postmenopausal Japanese women. J Bone Miner Res 13:1569 –1576; 1998.
The Genetics of Osteoporosis S. H. RALSTON Department of Medicine and Therapeutics, University of Aberdeen, Aberdeen, Scotland, UK
Importance of Genetics in Osteoporosis
Candidate Genes for Regulation of Bone Mass
Genetic factors play an important role in the pathogenesis of osteoporosis. Studies in twins and in normal families indicate that between 75% and 85% of the variance in bone mineral density (BMD) is under genetic control,22 and other markers of osteoporotic fracture risk such as ultrasound attenuation and bone turnover also appear to be genetically determined.2,14 This indicates that the effects of heredity on osteoporotic fracture risk extend beyond those on bone mass alone, which is consistent with the clinical observation that a family history of hip fracture predicts osteoporotic fracture independently from bone mass. The molecular-genetic basis by which bone mass and other aspects of fracture risk is determined remains poorly understood, but it is thought that many genes, each with small effects, may be responsible, rather than a small number of genes with large effects.10
The vitamin D receptor gene (VDR) is the most widely studied candidate gene. Three common single-nucleotide polymorphisms (SNP) have been described in the 39 region of VDR, recognized by the enzymes BsmI, ApaI, and TaqI. These polymorphisms have been associated with bone density in some populations, but not in others.4 Environmental factors such as calcium and vitamin D intake can modify the effects of VDR alleles on calcium metabolism, and it has been suggested that the relationship between VDR genotype and bone mass may be masked in populations with a high calcium intake.19 Another SNP has been described in exon 2 of VDR, recognized by the enzyme FokI. This SNP generates an alternative translation start site, resulting in production of a variant protein.1 The exon 2 polymorphism has been associated with bone mass and bone loss in some populations, but in others, no effect has been found.6,9 Polymorphisms of several other candidate genes such as interleukin-6 (IL-6),18 transforming factor-beta (TGF-b),16,26 the oestrogen receptor-alpha (ERa) gene,15 the calcitonin receptor gene,17 the apolipoprotein E gene (APOE),21 and the osteocalcin gene5 have also been associated with bone mass and/or osteoporotic fracture in various studies. A variable number tandem repeat polymorphism in the IL-6 gene was associated with peak bone mass in one population,18 but this has not yet been studied in other populations. An intronic polymorphism of the TGF-b gene has recently been found to be associated with very low bone mass and osteoporotic fracture in a Danish population,16 and a another group has identified a coding polymorphism that is related to bone mass and osteoporotic fracture in a Japanese population.26 The coding polymorphism is of interest in that it seems to influence serum levels of TGF-b. A coding polymorphism that affects the calcitonin receptor gene has been described that is associated with bone mass in Italian women. The relationship between this polymorphism and bone density in other populations remains to be described. Polymorphisms of the APOE gene have also been associated with bone mass.21 Although the mechanism responsible for this association remains unclear, it has been speculated to involve an alteration in transport of the fat soluble vitamin K, which is necessary for carboxylation of osteocalcin, an osteoblast-specific protein. A polymorphism has been identified in the promoter region of the osteocalcin gene which has been found to relate to bone mass in a Japanese study,5 although this has not been investigated in other populations. Polymorphisms of the ERa gene have been fairly extensively studied in relation to bone mass.19 Two common polymorphisms have been described in the first intron of the ER gene, recognized by the enzymes PvuII and XbaI, and these are in linkage disequilibrium with another TA repeat polymorphism in the promoter. In some populations, ER PvuII and XbaI genotypes
Ways of Identifying Genes That Regulate Bone Mass Linkage analysis provides an efficient way to identify disease genes in simple Mendelian disorders, and a family has recently been identified where high bone mass (Z-score . 13.0) was inherited as an autosomal dominant trait over several generations. A genome search using classical linkage techniques in this family showed the presence of a candidate locus on chromosome 11q12-13,13 although the gene responsible remains to be defined. Similar studies have been conducted in families where low bone mass was inherited in an autosomal dominant fashion. In these studies, nonparametric analysis showed evidence of linkage to a locus on chromosome 1p36 and possible evidence of linkage to two other loci on chromosomes 2p23 and 4qter. Analysis of allele sharing in sibling pairs on a genome-wide basis provides an alternative approach to defining disease genes and has the advantage that no assumptions need be made as to the mode of inheritance. Genome-wide searches for candidate loci that determine bone mass are currently underway in humans, but the results of these studies have not yet been reported. Genetic mapping studies in experimental animals provide a further approach to identify the genes responsible for regulation of bone mass. Although these studies are underway, the results have not yet been published. The candidate gene approach provides a fourth way to define the genetic basis of complex diseases, and this has been extensively studied in the osteoporosis field as summarized below.
Address for correspondence and reprints: Stuart H. Ralston, M.D., F.R.C.P., Department of Medicine and Therapeutics, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland. E-mail: [email protected] © 1999 by Elsevier Science Inc. All rights reserved.
85
8756-3282/99/$20.00 PII S8756-3282(99)00115-5
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S. H. Ralston Genetics of osteoporosis
have been significantly associated with bone mass in some populations,15,24 whereas in others, no effect has been found.11 The polymorphic TA repeat polymorphism has been associated with bone mass in one study,20 but this result has not yet been confirmed in other populations. The mechanisms by which these polymorphisms associate with bone mass are unclear. Although it is unlikely that the intronic polymorphisms have functional effects, the TA polymorphism could play a role in gene regulation. The collagen type I genes are further candidates for genetic regulation of bone mass since mutations in the protein coding regions of these genes give rise to a severe osteoporotic phenotype in the form of osteogenesis imperfecta. Although the collagen protein chains have been found to be normal in most osteoporotic patients, a polymorphism has recently been identified in a regulatory region of the COLIA1 gene which is more common in osteoporotic patients than in normal individuals.8 This polymorphism is situated at a binding site for the transcription factor Sp1 in the first intron of COLIA1, and has been found to be associated with bone mass and osteoporotic fracture in several Caucasian populations.7,8,23 This polymorphism is of interest since the association with fracture is much stronger than can be explained by genotype specific differences in bone mass. This raises the possibility that COLIA1 alleles may predispose to fracture by affecting other determinants of fracture risk such as bone quality or skeletal geometry. In this regard, preliminary data suggest that the polymorphism alters the affinity of Sp1 binding to DNA, transcription of the COLIA1 gene, and the production of the collagen aI protein chain. It is of interest that the COLIA1 polymorphism seems to be absent from Asian and African populations, which have low rates of osteoporotic fracture.3 Since segregation analysis suggests that several genes may combined to regulate bone mass, clinical studies have also looked at the possibility that genetic polymorphisms may interact to predict bone mass. Most work in this area has focused on the VDR and ERa genes, where combining information from SNPs in both genes has been found to identify subgroups of individuals with low and high bone mass.12,25 Clinical Applications for Genetic Studies Studies on the genetic basis of osteoporosis are in their infancy and much further work needs to be done to discover other genes that regulate bone mass and the mechanisms by which they do so. The results of these studies have clinical relevance, not only in identifying informative polymorphisms, which could be of value in the assessment of osteoporotic fracture risk, and predicting response to treatment, but also in uncovering new molecular targets for therapeutic intervention in the prevention and treatment of osteoporosis. References 1. Arai, H., Miyamoto, K.-I., Taketani, Y., et al. A vitamin D receptor gene polymorphism in the translation initiation codon: Effect on protein activity and relation to bone mineral density in Japanese women. J Bone Miner Res 12:915–921; 1997. 2. Arden, N. K., Baker, J., Hogg, C., Baan, K., and Spector, T. D. The heritability of bone mineral density, ultrasound of the calcaneus and hip axis length: a study of postmenopausal twins. J Bone Miner Res 11:530 –534; 1996. 3. Beavan, S., Prentice, A., Dibba, B., Yan, L., Cooper, C., and Ralston, S. H. Polymorphism of the collagen type I alpha 1 gene and ethnic differences in hip-fracture rates. N Engl J Med 339:351–352; 1998. 4. Cooper, G. S. and Umbach, D. M. Are vitamin D receptor polymorphisms associated with bone mineral density? A meta-analysis. J Bone Miner Res 11:1841–1849; 1996.
Bone Vol. 25, No. 1 July 1999:85– 86 5. Dohi, Y., Masayuki, I., Ohgushi, H., et al. A novel polymorphism in the promoter region for the human osteocalcin gene: the possibility of a correlation with bone mineral density in postmenopausal Japanese women. J Bone Miner Res 13:1633–1639; 1998. 6. Eccleshall, T. R., Garnero, P., Gross, C., Delmas, P. D., and Feldman, D. Lack of correlation between start codon polymorphism of the vitamin D receptor gene and bone mineral density in premenopausal French women: the OFELY study. J Bone Miner Res 13:31–35; 1998. 7. Garnero, P., Borel, O., Grant, S. F. A., Ralston, S. H., and Delmas, P. D. Collagen I a 1 polymorphism, Bone Mass and Bone Turnover in Healthy French Pre-Menopausal Women: The OFELY study. J Bone Miner Res 13:813– 818; 1998. 8. Grant, S. F. A., Reid, D. M., Blake, G., Herd, R., Fogelman, I., and Ralston, S. H. Reduced bone density and osteoporosis associated with a polymorphic Sp1 site in the collagen type I alpha 1 gene. Nature Genetics 14:203–205; 1996. 9. Gross, C., Eccleshall, T. R., Malloy, P. J., Villa, M. L., Marcus, R., and Feldman, D. The presence of a polymorphism at the translation initiation site of the vitamin D receptor gene is associated with low bone mineral density in postmenopausal Mexican-American women. J Bone Miner Res 12:1850 –1856; 1997. 10. Gueguen, R., Jouanny, P., Guillemin, F., Kuntz, C., Pourel, J., and Siest, G. Segregation analysis and variance components analysis of bone mineral density in healthy families. J Bone Miner Res 12:2017–2022; 1995. 11. Han, K. O., Moon, I. G., Kang, Y. S., Chung, H. Y., Min, H. K., and Han, I. K. Nonassociation of estrogen receptor genotypes with bone mineral density and estrogen responsiveness to hormone replacement therapy in Korean postmenopausal women [see comments]. J Clin Endocrinol Metab 82:991–995; 1997. 12. Gennari, L., Becherini, L., Masi, L., Mansani, R., Gonnelli, S., Cepollaro, C., Martini, S., Montagnani, A., Lentini, G., Becorpi, A. M., and Brandi, M. L. Vitamin D and estrogen receptor allelic variants in Italian postmenopausal women: evidence of multiple gene contribution to bone mineral density. J Clin Endocrinol Metab 83:939 –944; 1998. 13. Johnson, M. L., Gong, G., Kimberling, W., Recker, S., Kimmel, D. B., and Recker, R. R. Linkage of a gene causing high bone mass to human chromosome 11 (11q12-13). Am J Hum Genet 60:1326 –1332; 1997. 14. Kelly, P. J., Hopper, J. L., Macaskill, G. T., Pocock, N. A., Sambrook, P. N., and Eisman, J. A. Genetic factors in bone turnover. J Clin Endocrinol Metab 72:808 – 813; 1991. 15. Kobayashi, S., Inoue, S., Hosoi, T., Ouchi, Y., Shiraki, M., and Orimo, H. Association of bone mineral density with polymorphism of the estrogen receptor gene. J Bone Miner Res 11:306 –311; 1996. 16. Langdahl, B. L., Knudsen, J. Y., Jensen, H. K., Gregersen, N., and Eriksen, E. F. A sequence variation: 713-8delC in the transforming growth factor-beta 1 gene has higher prevalence in osteoporotic women than in normal women and is associated with very low bone mass in osteoporotic women and increased bone turnover in both osteoporotic and normal women. Bone 20:289 –294; 1997. 17. Masi, L., Becherini, L., Colli, E., et al. Polymorphisms of the calcitonin receptor gene are associated with bone mineral density in postmenopausal Italian women. Biochem Biophys Res Commun 248:190 –195; 1998. 18. Murray, R. E., McGuigan, F., Grant, S. F. A., Reid, D. M., and Ralston, S. H. Polymorphisms of the interleukin-6 gene are associated with bone mineral density. Bone 21:89 –92; 1997. 19. Ralston, S. H. The genetics of osteoporosis. Q J Med 90:247–251; 1997. 20. Sano, M., Inoue, S., Hosoi, T., et al. Association of estrogen receptor dinucleotide repeat polymorphism with osteoporosis. Biochem Biophys Res Commun 217:378 –383; 1995. 21. Shiraki, M., Shiraki, Y., Aoki, C., et al. Association of bone mineral density with apoplipoprotein E phenotype. J Bone Miner Res 12:1438 –1445; 1997. 22. Soroko, S. B., Barret-Connor, E., Edelstein, S. L., and Kritz-Silverstein, D. Family history of osteoporosis and bone mineral density at the axial skeleton: The Rancho Bernardo study. J Bone Miner Res 9:761–769; 1994. 23. Uitterlinden, A. G., Burger, H., Huang, Q., et al. Relation of alleles of the collagen type I a 1 gene to bone density and risk of osteoporotic fractures in postmenopausal women. N Engl J Med 338:1016 –1022; 1998. 24. Willing, M., Sowers, M., Aron, D., et al. Bone mineral density and its change in white women: estrogen and vitamin D receptor genotypes and their interaction. J Bone Miner Res 13:695–705; 1998. 25. Willing, M., Sowers, M., Aron, D., et al. Bone mineral density and its change in white women: estrogen and vitamin D receptor genotypes and their interaction. J Bone Miner Res 13:695–705; 1998. 26. Yamada, Y., Miyauchi, A., Goto, J., et al. Association of a polymorphism of the transforming growth factor-betal gene with genetic susceptibility to osteoporosis in postmenopausal Japanese women. J Bone Miner Res 13:1569 –1576; 1998.