Targeted Linked-Read Sequencing for Direct Haplotype Phasing of Parental GJB2/SLC26A4 Alleles: A Universal and Dependable Noninvasive Prenatal Diagnosis Method Applied to Autosomal Recessive Nonsyndromic Hearing Loss in At-Risk Families

Noninvasive prenatal diagnosis (NIPD) for autosomal recessive nonsyndromic hearing loss (ARNSHL) has been rarely reported until recent years. However, the previous method could not be performed on challenging genome loci (e.g. CNVs, deletions, inversions, or gene recombinants) or on families without proband genotype. Here, this study assesses the performance of relative haplotype dosage analysis (RHDO)-based NIPD for identifying fetal genotyping in pregnancies at risk of ARNSHL. Fifty couples carrying pathogenic variants associated with ARNSHL in either GJB2 or SLC26A4 were recruited. The RHDO-based targeted linked-read sequencing combined with whole gene coverage probes was used to genotype the fetal cell-free DNA (cfDNA) of 49 families that met the quality control standard.. Fetal amniocyte samples were genotyped using invasive prenatal diagnosis (IPD) to assess the performance of NIPD. The NIPD results showed 100%(49/49) concordance with those obtained through IPD. Two families with copy number variation and recombination were also successfully identified. Sufficient specific informative SNPs for haplotyping, as well as the fetal cfDNA concentration and sequencing depth, are prerequisites for RHDO-based NIPD. This method has the merits of covering the entire genes of GJB2 and SLC26A4, qualifying for copy number variation and recombination analysis with remarkable sensitivity and specificity. Therefore, it has clinical potential as an alternative to traditional IPD for ARNSHL.