title: Post-genome wide association studies and functional analyses identify association of MPP7 gene variants with site-specific bone mineral density.
abstract: Our previous genome-wide association study (GWAS) in a Hong Kong Southern Chinese population with extreme bone mineral density (BMD) scores revealed suggestive association with MPP7, which ranked second after JAG1 as a candidate gene for BMD. To follow-up this suggestive signal, we replicated the top single-nucleotide polymorphism rs4317882 of MPP7 in three additional independent Asian-descent samples (n= 2684). The association of rs4317882 reached the genome-wide significance in the meta-analysis of all available subjects (P(meta)= 4.58 × 10(-8), n= 4204). Site heterogeneity was observed, with a larger effect on spine than hip BMD. Further functional studies in a zebrafish model revealed that vertebral bone mass was lower in an mpp7 knock-down model compared with the wide-type (P= 9.64 × 10(-4), n= 21). In addition, MPP7 was found to have constitutive expression in human bone-derived cells during osteogenesis. Immunostaining of murine MC3T3-E1 cells revealed that the Mpp7 protein is localized in the plasma membrane and intracytoplasmic compartment of osteoblasts. In an assessment of the function of identified variants, an electrophoretic mobility shift assay demonstrated the binding of transcriptional factor GATA2 to the risk allele 'A' but not the 'G' allele of rs4317882. An mRNA expression study in human peripheral blood mononuclear cells confirmed that the low BMD-related allele 'A' of rs4317882 was associated with lower MPP7 expression (P= 9.07 × 10(-3), n= 135). Our data suggest a genetic and functional association of MPP7 with BMD variation.
authors.affiliation: Department of Medicine, The University of Hong Kong, Hong Kong, China.
authors.forename: Su-Mei
authors.initials: SM
authors.lastname: Xiao
authors.forename: Annie Wai Chee
authors.initials: AW
authors.lastname: Kung
authors.forename: Yi
authors.initials: Y
authors.lastname: Gao
authors.forename: Kam-Shing
authors.initials: KS
authors.lastname: Lau
authors.forename: Alvin
authors.initials: A
authors.lastname: Ma
authors.forename: Zhen-Lin
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Liu
authors.forename: Wiebo
authors.initials: W
authors.lastname: Xia
authors.forename: Jin-Wei
authors.initials: JW
authors.lastname: He
authors.forename: Lin
authors.initials: L
authors.lastname: Zhao
authors.forename: Min
authors.initials: M
authors.lastname: Nie
authors.forename: Wei-Zhen
authors.initials: WZ
authors.lastname: Fu
authors.forename: Min-Jia
authors.initials: MJ
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Johnny S H
authors.initials: JS
authors.lastname: Kwan
authors.forename: Gloria Hoi Wan
authors.initials: GH
authors.lastname: Tso
authors.forename: Zhi-Jie
authors.initials: ZJ
authors.lastname: Dai
authors.forename: Ching-Lung
authors.initials: CL
authors.lastname: Cheung
authors.forename: Cora H
authors.initials: CH
authors.lastname: Bow
authors.forename: Anskar Yu Hung
authors.initials: AY
authors.lastname: Leung
authors.forename: Kathryn Choon Beng
authors.initials: KC
authors.lastname: Tan
authors.forename: Pak Chung
authors.initials: PC
authors.lastname: Sham
mesh_terms: D000483:Alleles; D000818:Animals; D001665:Binding Sites; D015519:Bone Density / Q000235:genetics*; D002460:Cell Line; D005260:Female; D050989:GATA2 Transcription Factor / Q000378:metabolism; D015894:Genome, Human; D055106:Genome-Wide Association Study; D005838:Genotype; D060148:HapMap Project; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000378:metabolism; D015027:Zebrafish / Q000235:genetics; D029961:Zebrafish Proteins / Q000235:genetics
chemical_list: D050989:GATA2 Transcription Factor; C482290:MPP7 protein, human; D008565:Membrane Proteins; D012333:RNA, Messenger; D029961:Zebrafish Proteins