mTORC1 activation in preosteoblasts produces immature woven bone.

<p>(A) PCR analysis of <i>Tsc1</i> allele recombination in tissues from <i>Osx</i>-<i>GFP</i>::<i>Cre</i>^TG/+;<i>Tsc1</i>^flox/flox mice (Δ<i>Tsc1</i> mice). Primers for <i>GAPDH</i> were used as a loading control. (B) Immunohistochemical staining of S6 phosphorylation (Ser235/236) in sections of distal femur from 10-week-old control and Δ<i>Tsc1</i> mice. (C) The 10-week-old Δ<i>Tsc1</i> mouse had a square skull (the result of hyperplasia of the osteoid, a typical manifestation of rickets) compared with the control littermate. (D) Plain X-ray examination of a 4-week-old Δ<i>Tsc1</i> mouse revealed a smaller skeleton and higher bone mass compared with the control littermate. (E) Body weight of 4-week-old control and Δ<i>Tsc1</i> mice. (F) Representative images of micro-CT analyses of the structure of metaphyseal trabecular bone and cortical bone in the distal femur showed increased bone mass, but more porous areas (indicating more hypomineralized areas) in Δ<i>Tsc1</i> mice. (G, H) Goldner’s Masson trichrome staining of distal femur showed more osteoid/hypomineralized areas (stained red) in bone of Δ<i>Tsc1</i> mice. Boxed area is enlarged in the panel below. The dotted line marked boundary of the red osteoid. OS/BS, osteoid per bone surface. Scale bar, 100μm.