title: Systems genetic analysis of osteoblast-lineage cells.
abstract: The osteoblast-lineage consists of cells at various stages of maturation that are essential for skeletal development, growth, and maintenance. Over the past decade, many of the signaling cascades that regulate this lineage have been elucidated; however, little is known of the networks that coordinate, modulate, and transmit these signals. Here, we identify a gene network specific to the osteoblast-lineage through the reconstruction of a bone co-expression network using microarray profiles collected on 96 Hybrid Mouse Diversity Panel (HMDP) inbred strains. Of the 21 modules that comprised the bone network, module 9 (M9) contained genes that were highly correlated with prototypical osteoblast maker genes and were more highly expressed in osteoblasts relative to other bone cells. In addition, the M9 contained many of the key genes that define the osteoblast-lineage, which together suggested that it was specific to this lineage. To use the M9 to identify novel osteoblast genes and highlight its biological relevance, we knocked-down the expression of its two most connected "hub" genes, Maged1 and Pard6g. Their perturbation altered both osteoblast proliferation and differentiation. Furthermore, we demonstrated the mice deficient in Maged1 had decreased bone mineral density (BMD). It was also discovered that a local expression quantitative trait locus (eQTL) regulating the Wnt signaling antagonist Sfrp1 was a key driver of the M9. We also show that the M9 is associated with BMD in the HMDP and is enriched for genes implicated in the regulation of human BMD through genome-wide association studies. In conclusion, we have identified a physiologically relevant gene network and used it to discover novel genes and regulatory mechanisms involved in the function of osteoblast-lineage cells. Our results highlight the power of harnessing natural genetic variation to generate co-expression networks that can be used to gain insight into the function of specific cell-types.
authors.affiliation: Center for Public Health Genomics, University of Virginia, Charlottesville, Virginia, United States of America.
authors.forename: Gina
authors.initials: G
authors.lastname: Calabrese
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Bennett
authors.forename: Luz
authors.initials: L
authors.lastname: Orozco
authors.forename: Hyun M
authors.initials: HM
authors.lastname: Kang
authors.forename: Eleazar
authors.initials: E
authors.lastname: Eskin
authors.forename: Carlos
authors.initials: C
authors.lastname: Dombret
authors.forename: Olivier
authors.initials: O
authors.lastname: De Backer
authors.forename: Aldons J
authors.initials: AJ
authors.lastname: Lusis
authors.forename: Charles R
authors.initials: CR
authors.lastname: Farber
mesh_terms: D000818:Animals; D015519:Bone Density / Q000235:genetics; D002460:Cell Line; D019070:Cell Lineage / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D055106:Genome-Wide Association Study; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D040641:Quantitative Trait Loci; D051155:Wnt1 Protein / Q000037:antagonists & inhibitors; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D051155:Wnt1 Protein; C486541:Maged1 protein, mouse; C485539:Sfrp1 protein, mouse; D000094742:Secreted Frizzled-Related Proteins