However, we did not note a further apparent reduction in E18.5 kidney size when comparing Esrp1‐/‐;Esrp2+/+ mice to Esrp1‐/‐ mice that had a heterozygous or null allele for Esrp2. Interestingly, as we generated large numbers of mutants, we noted that a significant number of mice with Esrp1‐/‐ genotypes had unilateral renal aplasia, whereas all mice with at least one wild‐type (WT) Esrp1 allele had two kidneys, independent of the Esrp2 allele (Table 1). The gene discussed is ESRP1; the disease is renal agenesis.