Decreased proliferation, but not apoptosis, is responsible for reduction of growth plate height.

<p>(A) Hoechst labeling and immunofluorescence of proximal humerus growth plate from WT and Line 2 samples, showing Ki67 positive cells in the proliferating zone (PZ) (red boxes), and resting zone (RZ) (white box). 2° Ab is a section stained with secondary antibody only and Hoechst. Lower panel shows the proliferative zone (red box) and part of the resting zone (blue box) under higher magnification, highlighting the difference in Ki67 positive cells within the proliferative zone of WT and Tg mice (B) Quantification of Ki67 positive cells from Line 2 proximal humerus growth plates demonstrated a clear reduction in the number of proliferating cells in the proliferating zone compared to the resting zone. WT (n = 6), Line 2 (n = 6); ***p≤0.001 (C) Quantification of TUNEL positive cells shows no difference in apoptotic cells in either the proliferating or hypertrophic zones. (D) Gene expression for apoptotic markers, <i>Bax</i> and <i>Bcl2,</i> from 14.5 dpc limbs confirms lack of increased apoptosis.