Non‐invasive prenatal diagnosis of Duchenne and Becker muscular dystrophies by relative haplotype dosage†

OBJECTIVE Development of an accurate and affordable test for the non-invasive prenatal diagnosis of Duchenne and Becker muscular dystrophies (DMD/BMD) to implement in clinical practice. METHOD Cell-free DNA was extracted from maternal blood and prepared for massively parallel sequencing on an Illumina MiSeq by targeted capture enrichment of single nucleotide polymorphisms (SNPs) across the dystrophin gene on chromosome X. Sequencing data were analysed by relative haplotype dosage. RESULTS Seven healthy pregnant donors and two pregnant DMD carriers all bearing a male fetus were recruited through the non-invasive prenatal diagnosis for single gene disorders study. Non-invasive prenatal diagnosis testing was conducted by relative haplotype dosage analysis for X-linked disorders where the genomic DNA from the chorionic villus sampling (for healthy pregnant donors) or from the proband (for pregnant DMD carriers) was used to identify the reference haplotype. Results for all patients showed a test accuracy of 100%, when the calculated fetal fraction was >4% and correlated with known outcomes. A recombination event was also detected in a DMD patient. CONCLUSION Our new test for NIPD of DMD/BMD has been shown to be accurate and reliable during initial stages of validation. It is also feasible for implementation into clinical service.