Exon -64 (counted from the last exon backwards) was targeted for the insertion of a 16 bp sequence with an sgRNA and a template oligonucleotide using CRSIPR/Cas9 technology. The inserted sequence contains stop codons in all three reading frames and a diagnostic EcoRI restriction site and was inserted after glutamine codon 5328, 131 bp into the exon. The result is an allele where the Nes1g (nesprin 1 giant) splice variants have a premature stop codon. Immunoblots showed a complete absence of giant isoforms in brain lysates. (J:268589)