Mutational spectrum in patients with dominant non-syndromic hearing loss in Austria

Purpose Hearing loss (HL) is often monogenic. The clinical importance of genetic testing in HL may further increase when gene therapy products become available. Diagnoses are, however, complicated by a high genetic and allelic heterogeneity, particularly of autosomal dominant (AD) HL. This work aimed to characterize the mutational spectrum of AD HL in Austria. Methods In an ongoing prospective study, 27 consecutive index patients clinically diagnosed with non-syndromic AD HL, including 18 previously unpublished cases, were analyzed using whole-exome sequencing (WES) and gene panels. Novel variants were characterized using literature and bioinformatic means. Two additional Austrian medical centers provided AD HL mutational data obtained with in-house pipelines. Other Austrian cases of AD HL were gathered from literature. Results The solve rate (variants graded as likely pathogenic (LP) or pathogenic (P)) within our cohort amounted to 59.26% (16/27). MYO6 variants were the most common cause. One third of LP/P variants were truncating variants in haploinsufficiency genes. Ten novel variants in HL genes were identified, including six graded as LP or P. In one cohort case and one external case, the analysis uncovered previously unrecognized syndromic presentations. Conclusion More than half of AD HL cases analyzed at our center were solved with WES. Our data demonstrate the importance of genetic testing, especially for the diagnosis of syndromic presentations, enhance the molecular knowledge of genetic HL, and support other laboratories in the interpretation of variants. Supplementary Information The online version contains supplementary material available at 10.1007/s00405-024-08492-5.

Girl with sporadic prelingual moderate-to-severe HL.Age at the time of the screening: 1 y.

Pipeline
The DNA was isolated from blood as described for Ext-1.The GJB2 gene was screened using PCR and Sanger.

Patient Ext-3 Clinical features
Girl with prelingual profound HL and mild pigmentation anomalies.Café-au-lait spots.

Pipeline
Clinical exome sequencing (TruSight One Expanded Sequencing Panel, Illumina) of 6713 clinically relevant genes followed by analysis of genes related to HL based on HPO terms.

(b) Institution 2 Patient Ext-4 Clinical features
Slowly progressive HL with an onset at school age.A dominant inheritance could be inferred from the family anamnesis (father with profound HL since age 49 years; three out of four children affected).
In 2018 (aged 48 years), the index patient had bilateral severe-toprofound HL across all frequencies with a more pronounced loss in the high frequencies.

Pipeline
WES was performed as described in PMID: 31059585.S4b.

Patient Ext-5 Clinical features
The clinical features of the patient are presented in PMID: 29320412 (patient #610).In brief, the female patient developed sudden HL at the age of 27 years.The HL is symmetric, moderate-to-severe in the low frequencies and profound in the high frequencies.An autosomal dominant inheritance was deduced from the family tree.

Pipeline
DNA was extracted from peripheral blood as described in PMID: 29320412.Prior to WES, the coding sequences of the following genes were analyzed using PCR amplification followed by Sanger sequencing; GJB2, GJB6, SLC26A4, FOXI1, POU3F4, KCNJ10, POU4F3, and COCH, based on the clinical finding of a bilateral enlarged vestibular aqueduct.The SLC26A3 CEVA haplotype was assessed using a SNP assay, and multiplex PCR was used for the detection of common deletions in GJB6.Following negative results, WES was performed as described in PMID: 31059585.

Figure
FigureS1 (a-c).Pedigrees and audiograms of all previously unpublished families from our cohort.Shaded symbols: affected.Unshaded symbols: unaffected.The genotype of all family members tested by WES and/or Sanger sequencing is indicated by +/+ (homozygous wildtype) or +/-(heterozygous for the candidate causative variant).A question mark indicates that the affected status of an individual is unknown.(A) Individual IV.5 does not carry GSDME c.991-15_991-13del but is heterozygous for GJB2 NM_004004.6:c.35delG.

Figure S1 .
Figure S1.(n-q).Pedigrees and audiograms of all previously unpublished families.(q) Individual III.5 is affected by HL, the etiology of which was considered unclear due to a previous encephalitis.

Table S2 .
Gene panel.AD HL genes targeted in the virtual gene panel.