Physiol. Genomics 35: 191-196, 2008.
First published August 26, 2008; doi:10.1152/physiolgenomics.90237.2008
1094-8341/08 $8.00
Received 2 May 2008;
accepted in final form 20 August 2008.
Physiological Genomics 35:191-196 (2008)
1094-8341/08 $8.00 © 2008 American Physiological Society
Genomic expression analysis of rat chromosome 4 for skeletal traits at femoral neck
Imranul Alam
1,
Qiwei Sun
1,
Lixiang Liu
2,
Daniel L. Koller
2,
Yunlong Liu
3,
Howard J. Edenberg
2,4,
Michael J. Econs
2,3,
Tatiana Foroud
2 and
Charles H. Turner
1
1 Department of Biomedical Engineering, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana
2 Departments of Medical and Molecular Genetics, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana
3 Department of Medicine, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana
4 Departments of Biochemistry and Molecular Biology, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana
Hip fracture is the most devastating osteoporotic fracture type with significant morbidity and mortality. Several studies in humans and animal models identified chromosomal regions linked to hip size and bone mass. Previously, we identified that the region of 4q21-q41 on rat chromosome (Chr) 4 harbors multiple femoral neck quantitative trait loci (QTLs) in inbred Fischer 344 (F344) and Lewis (LEW) rats. The purpose of this study is to identify the candidate genes for femoral neck structure and density by correlating gene expression in the proximal femur with the femoral neck phenotypes linked to the QTLs on Chr 4. RNA was extracted from proximal femora of 4-wk-old rats from F344 and LEW strains, and two other strains, Copenhagen 2331 and Dark Agouti, were used as a negative control. Microarray analysis was performed using Affymetrix Rat Genome 230 2.0 arrays. A total of 99 genes in the 4q21-q41 region were differentially expressed (P < 0.05) among all strains of rats with a false discovery rate <10%. These 99 genes were then ranked based on the strength of correlation between femoral neck phenotypes measured in F2 animals, homozygous for a particular strain's allele at the Chr 4 QTL and the expression level of the gene in that strain. A total of 18 candidate genes were strongly correlated (r2 > 0.50) with femoral neck width and prioritized for further analysis. Quantitative PCR analysis confirmed 14 of 18 of the candidate genes. Ingenuity pathway analysis revealed several direct or indirect relationships among the candidate genes related to angiogenesis (VEGF), bone growth (FGF2), bone formation (IGF2 and IGF2BP3), and resorption (TNF). This study provides a shortened list of genetic determinants of skeletal traits at the hip and may lead to novel approaches for prevention and treatment of hip fracture.
quantitative trait loci; gene expression; microarray; bone density; hip fracture
Copyright © 2008 by the American Physiological Society.