We do not believe that this loss of p53 in RP mutants is simply due to the inability of the cells to make protein per se, for in other zebrafish models of ribosome biogenesis deficiency such as nucleostemin, gnl2, and nop10 mutants we are able to visualize robust p53 stabilization by western blot analysis even in the absence of ionizing radiation up until 4 dpf [5,6]. This evidence concerns the gene GNL2 and hyperinsulinemic hypoglycemia, familial, 4.