title: Congenic mice provide in vivo evidence for a genetic locus that modulates serum insulin-like growth factor-I and bone acquisition.
abstract: We identified quantitative trait loci (QTL) that determined the genetic variance in serum IGF-I through genome-wide scanning of mice derived from C57BL/6J(B6) x C3H/HeJ(C3H) intercrosses. One QTL (Igf1s2), on mouse chromosome 10 (Chr10), produces a 15% increase in serum IGF-I in B6C3 F2 mice carrying c3 alleles at that position. We constructed a congenic mouse, B6.C3H-10 (10T), by backcrossing c3 alleles from this 57-Mb region into B6 for 10 generations. 10T mice have higher serum and skeletal IGF-I, greater trabecular bone volume fraction, more trabeculae, and a higher number of osteoclasts at 16 wk, compared with B6 (P < 0.05). Nested congenic sublines generated from further backcrossing of 10T allowed for recombination and produced four smaller sublines with significantly increased serum IGF-I at 16 wk (i.e. 10-4, 10-7, 10-10, and 10-13), compared with B6 (P < 0.0003), and three smaller sublines that showed no differences in IGF-I vs. age- and gender-matched B6 mice. Like 10T, the 10-4 nested sublines at 16 wk had higher femoral mineral (P < 0.0001) and greater trabecular connectivity density with significantly more trabeculae than B6 (P < 0.01). Thus, by comprehensive phenotyping, we were able to narrow the QTL to an 18.3-Mb region containing approximately 148 genes, including Igf1 and Elk-3(ETS domain protein). Allelic differences in the Igf1s2 QTL produce a phenotype characterized by increased serum IGF-I and greater peak bone density. Congenic mice establish proof of concept of shared genetic determinants for both circulating IGF-I and bone acquisition.
authors: The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA.
authors: K M
authors: KM
authors: Delahunty
authors: K L
authors: KL
authors: Shultz
authors: G A
authors: GA
authors: Gronowicz
authors: B
authors: B
authors: Koczon-Jaremko
authors: M L
authors: ML
authors: Adamo
authors: L G
authors: LG
authors: Horton
authors: J
authors: J
authors: Lorenzo
authors: L R
authors: LR
authors: Donahue
authors: C
authors: C
authors: Ackert-Bicknell
authors: B E
authors: BE
authors: Kream
authors: W G
authors: WG
authors: Beamer
authors: C J
authors: CJ
authors: Rosen