Figure 1.

Timing of agonist exposure in the ColI-Rs1–late mice. Double-transgenic ColI(2.3)+/Rs1+ mice expressing Rs1 from gestation develop a dramatic bone overgrowth phenotype even in the absence of agonist (4). ColI(2.3)+/Rs1+ mice expressing Rs1 after 4 wk of age (referred to here as ColI/Rs1–late mice) and in the absence of agonist (indicated by dashed lines) have grossly normal skeletons when examined through 30 wk of age. ColI/Rs1–late mice were either treated with continuous agonist exposure via an osmotic pump (referred to here as ColI/Rs1–late^Con mice) (A) or intermittent agonist exposure by daily injections of drug (referred to here as ColI/Rs1–late^Int mice) (B). Mice were analyzed after 10 wk of drug exposure at 20 wk of age. Dashed lines indicate the period without agonist exposure. The open box indicates the period of doxycycline administration to suppress Rs1 expression.