Leucine codons 1 and 6 (CTG) in the alpha isoform (which is translated from an alternative CTG initiation codon 173 codons upstream of the canonical ATG codon) were replaced with glycine codons GGA (p.L1G, p.L6G). The loxP site flanked neomycin resistance gene cassette that was inserted into intron 1 was removed through subsequent cre-mediated recombination. Western blot experiments confirmed the absence of alpha isoform peptide expression from this allele in the brain, while canonical isoform expression was unaffected.