A neomycin resistance gene, an in-frame HA epitope and a stop codon were inserted into exon 22, which encodes the spectrin binding domain. Northern blot analysis on RNA derived from homozygous brains demonstrated that no detectable transcript was expressed from this allele. Western blot analysis on homogenates of homozygous brain confirmed that no encoded protein was present. Nonsense-mediated decay leads to a reduction in the 220-kDa and giant Ank2 polypeptides.