Expression of Gas6 in the proliferative phase of NTN. RNA collected from four to eight representative mice on days 0–21 were subjected to Northern blotting. The expression of GAPDH served as a control for RNA loading. Representative results are shown in the upper panels. The graph shows densitometric analysis of Gas6 mRNA expression after normalization by the expression of GAPDH. The experiments were repeated three times and representative data are shown. **P < 0.01.