Bone Abstracts

Screening gene function in vivo is a powerful approach to discover novel drug targets in the human genome (Nat Rev Drug Discov 2 38–51, 2003). We present data for 3776 distinct gene knockout (KO) mouse lines with viable adult homozygous mice generated using both gene-trapping and homologous recombination technologies. Bone mass was determined from PIXImus DEXA scans of male and female mice at 14 weeks of age and by microCT analyses of bones from male mice at 16 weeks of age. Wild-type (WT) littermates were examined for each gene KO. For most lines DEXA scans were performed on four KO and two WT mice of each gender. Body BMC, aBMD, vBMD, and BMC:LBM ratio, femur BMD, and spine BMD were monitored. Bone parameters were normally distributed. Volumetric BMD in KOs (n=3629) averaged 99.5% of WT values with a S.D. of 3.7%. Using a Scanco Medical μCT40, trabecular bone parameters in LV5 were analyzed in 3381 lines and midfemur cortical thickness (CT) in 3345 lines (four KO and two WT). Specially designed plastic inserts held 48 LV5s (scanned overnight with 4 LV5s scanned simultaneously) and 18 femurs (scanned in 30 min with six femurs scanned simultaneously). LV5 trabecular BV/TV in KOs averaged 16.2% (S.D.=3.9%). Femoral CT averaged 245 μm (S.D.=16 μm). Since primary high-throughput screens (HTS) are susceptible to false positive findings, additional cohorts of mice from KO lines with intriguing HTS bone data were examined. Aging, ovariectomy, histomorphometry and bone strength studies were performed on lines identifying potentially novel osteoporosis drug targets, and possible non-skeletal phenotypes were explored. Together, these screens identified previously reported (Lrp5, Sost, Wnt10b, Sfrp4, myostatin, Klotho, c-Src, Ostm1, and Crtap) as well as novel (Wnt16, Lrrk1, Fam20c, sphingosine-1P-lyase, and claudin-18) genes regulating bone mass.