Oral Presentation 6th Australian Health and Medical Research Congress 2012

ENU-induced mutant mice models to identify novel molecules that regulate bone homeostasis (#185)

Jiake Xu 1
  1. School of Pathology and Laboratory Medicine, University Of Western Australia , Perth, WA, Australia

Over the past decade, the advancement of gene manipulation technologies has facilitated the use of mouse models to study bone homeostasis. Knockout, knock-in and transgenic mouse models have been widely used to identify genes that are vital in regulating bone homeostasis. More recently, chemical mutagenesis has been employed to develop and expand the repertoire of mutants for gene function studies. In this approach, N-ethyl-N-nitrosourea (ENU) mutagenesis, followed by screening methods to detect single-nucleotide substitutions within the targeted gene, represents a promising technology. We are currently screening mice for mutations that affect bone phenotype. We have identified several molecules that affect bone homeostasis in ENU-induced mutant mice; including CHKB, Roquin, BCL2 and Morc3. For example, choline kinase beta (chkb) mutant mice exhibit an osteoporotic phenotype as evidenced by microCT and histological assessment. In vivo and in vitro analysis reveals elevated osteoclast numbers in the mutant mice. Furthermore, osteoclasts from choline kinase beta mutant mice exhibit increased resorptive activity compared to those of littermate controls. Osteoclasts derived from choline kinase beta mutant mice showed decreased calcium signaling response to high extracellular calcium. This may account for the increased resorptive activity in osteoclasts derived from the mutant mice. Treatment with CDP-choline in vivo and in vitro reduces osteoclast numbers, thereby rescuing the osteoclast phenotype. In vitro assays show a reduction in bone mineralisation in osteoblast cultures derived from the bone marrow of mutant mice. Taken together, our data document, for the first time, that choline kinase beta plays an important role in bone homeostasis. Overall, this phenotype-driven screening approach enables us to utilize a novel and unique tool for the discovery of gene function in bone biology. The high-throughput sequencing-based screening techniquewill help unveil novel mutations that cause dysfunction of bone homeostasis, and potential molecular mechanism(s) underlying the fundamental activities of bone cells.