Using an allelic series of mice, we have shown that RERE deficiency leads to a spectrum of defects that includes microphthalmia, postnatal growth deficiency, brain hypoplasia, decreased numbers of NeuN-positive hippocampal neurons, hearing loss, cardiovascular malformations, spontaneous development of cardiac fibrosis and renal agenesis (Table 3). The gene discussed is RERE; the disease is fibrosis.