ABSTRACT
Previously, the DFNA21 locus was positioned telomeric to the DFNA13 locus based on testing of candidate loci. One family member in this region did not carry the at risk haplotype, although he had the same nonspecific midfrequency hearing impairment as other affected family members. Hence, we performed a whole genome linkage scan excluding other regions of the genome and confirming the localization of DFNA21 to 6p22.3-24.1. The DFNA21 interval was determined to span 12.4 Mb (approximately 22 cM) and is delimited on the telomeric side by BV097155 and on the centromeric side by D6S1691. A maximum lod score of 3.51 (theta = 0.066), was calculated for marker D6S1721. The DFNA21 region does not overlap the adjacent DFNA31 and DFNA13 loci and contains 31 known genes. The coding regions and exon-intron boundaries of four candidate genes, SOX4, MYLIP, CAP2, and RPEL1, were sequenced, but no mutations were identified.
