Supplementary Material for: Disruption of the ATE1 and SLC12A1 Genes by Balanced Translocation in a Boy with Non-Syndromic Hearing Loss

We report on a boy with non-syndromic hearing loss and an apparently balanced translocation t(10;15)(q26.13;q21.1). The same translocation was found in the normally hearing brother, father and paternal grandfather; however, this does not exclude its involvement in disease pathogenesis, for example, by unmasking a second mutation. Breakpoint analysis via FISH with BAC clones and long-range PCR products revealed a disruption of the arginyltransferase 1 (ATE1) gene on translocation chromosome 10 and the solute carrier family 12, member 1 gene (SLC12A1) on translocation chromosome 15. SNP array analysis revealed neither loss nor gain of chromosomal regions in the affected child, and a targeted gene enrichment panel consisting of 130 known deafness genes was negative for pathogenic mutations. The expression patterns in zebrafish and humans did not provide evidence for ear-specific functions of the ATE1 and SLC12A1 genes. Sanger sequencing of the 2 genes in the boy and 180 GJB2 mutation-negative hearing-impaired individuals did not detect homozygous or compound heterozygous pathogenic mutations. Our study demonstrates the many difficulties in unraveling the molecular causes of a heterogeneous phenotype. We cannot directly implicate disruption of ATE1 and/or SLC12A1 to the abnormal hearing phenotype; however, mutations in these genes may have a role in polygenic or multifactorial forms of hearing impairment. On the other hand, it is conceivable that our patient carries a disease-causing mutation in a so far unidentified deafness gene. Evidently, disruption of ATE1 and/or SLC12A1 gene function alone does not have adverse effects.

本研究报道一例非综合征型听力损失患儿，其携带外观平衡的易位t(10;15)(q26.13;q21.1)。该易位同时存在于其听力正常的兄弟、父亲及祖父体内，但这并不排除该易位参与疾病发病机制的可能，例如通过显露第二处突变的方式。利用细菌人工染色体（Bacterial Artificial Chromosome, BAC）克隆与长距聚合酶链式反应（PCR）产物进行荧光原位杂交（Fluorescence In Situ Hybridization, FISH）断点分析，结果显示易位染色体10上的精氨酰转移酶1（arginyltransferase 1, ATE1）基因，以及易位染色体15上的溶质载体家族12成员1（solute carrier family 12 member 1, SLC12A1）基因均发生断裂。单核苷酸多态性（Single Nucleotide Polymorphism, SNP）芯片分析显示，该患儿未出现染色体区域的缺失或重复；包含130个已知耳聋基因的靶向基因富集检测组未检出致病性突变。斑马鱼与人类的基因表达谱分析未发现ATE1及SLC12A1基因具有耳特异性功能的证据。对该患儿及180例GJB2突变阴性的听力受损个体的上述两个基因进行桑格测序（Sanger Sequencing），未检测到纯合或复合杂合致病性突变。本研究揭示了解析异质性表型分子病因所面临的诸多挑战。我们无法直接将ATE1和/或SLC12A1的基因断裂与该患儿的听力异常表型直接关联，但上述基因的突变可能在多基因或多因素型听力损失中发挥作用。另一方面，本研究中的患儿可能携带有迄今尚未被发现的耳聋致病基因突变。显然，仅破坏ATE1和/或SLC12A1的基因功能并不会产生不良影响。