Three premature stop codons, V31* (GTG to TAG), P32* (CCA to TGA), and D33* (GAC to TAA) were introduced in exon 2, which is expected to result in nonsense-mediated decay of mRNA, along with a loxP-flanked neomycin resistance gene following the mutated exon 2. The selection cassette was removed via cre-mediated recombination. This knock-in strategy was used to knock-out the gene without affecting the partially overlapping Slc25a35 gene (transcribed in opposite direction). RT-qPCR analysis shows 90% reduction in cardiac mRNA of homozygotes. Western blot analysis shows nearly complete loss of expression in homozygous heart.