Intriguingly, however, mice lacking COX-2 exhibit postnatal kidney pathologies associated with neonatal fatality, including nephron hypoplasia and atrophy, impaired cortical growth, and even cyst formation in multiple nephron segments—phenotypes suggestive of significant disruptions in renal ontogeny (Dinchuk et al., 1995; Morham et al., 1995; Mahler et al., 1996). The gene discussed is PTGER2; the disease is cyst.