Fig. 9. Quantification of protein expression in CycD1 and Chx10-null mice. (A) In CycD1-null retinas, Kip1 expression is present in more cells than normal. The increased percentage of cells positive for both Chx10 and Kip1 indicates that RPCs cannot maintain their normal low levels of Kip1 protein in the absence of CycD1. (B) In Chx10-null retinas, the percentages of cells expressing both CycD1 and Kip1 are abnormal. (C) Northern blot hybridization of total RNA from P0 retinas shows that the CycD1 mRNA level decreases in the Chx10-null compared with wild type. Ethidium bromide-stained 28s rRNA bands are shown as loading controls. ^*A statistically significant difference (P<0.05); ^**P<0.01; ^***P<0.0003.