Targeting of the α-adducin gene, Add1. (A) Structure of the α-adducin locus according to Ensembl transcript identification ENSMUST00000114340 with the targeted allele shown below. Numbered boxes represent exons. Relevant restriction sites are indicated. (B) Homologous recombination generates a 13.1-kb wild-type and a 9.0-kb mutant allele upon digestion of ES cell DNA with EcoRI. (C) Northern blot analysis of E14.5 fetal liver with hybridization probes indicated. RT-PCR primers used to generate probes are given in Table 1. +/+ indicates wild- type; +/−, heterozygotes; and −/−, homozygous null.