DMD genotyping. (A) Genomic DNA extracted from blood of wild-type (WT), heterozygote (carrier), and null (affected or xmd) dogs was used for PCR amplification.8 The PCR product containing the polymorphic Sau96I site (B) created by the mutation in the dystrophin gene was digested, electrophoresed, and visualized with ethidium bromide. The genotype of one DLA-matched pair of donor and recipient is shown here. D indicates donor; R, recipient. The wild-type band (310 bp) and the mutant band (150 bp) are marked with arrows. (B) Schematic of the wild-type and xmd mutant alleles. The cxmd allele has a point mutation (a to g) in the consensus splice acceptor site of intron 6. As a consequence, alternative splicing either skips exon 7 entirely (solid line) or splices into a cryptic site 5 nucleotides 3-prime of the original splice site (dashed line). Both of these predominant splice variants introduce frame-shifts and early termination codons. Exon probes (TAMRA and MGB) were designed to hybridize to the wild-type junction between exons 6 and 7 and to distinguish between normally spliced mRNA and the splice variants created by the cxmd mutation.
