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.本研究报告1例非综合征性听力损失（non-syndromic hearing loss）患儿，其携带表观平衡易位t(10;15)(q26.13;q21.1)。该易位同样存在于其听力正常的兄弟、父亲及祖父中，但这并不排除该易位参与疾病发病机制的可能，例如通过暴露第二处致病突变的方式。借助细菌人工染色体（Bacterial Artificial Chromosome, BAC）克隆与长距聚合酶链式反应（long-range PCR）产物开展荧光原位杂交（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基因（solute carrier family 12, member 1 gene, SLC12A1）均发生断裂。单核苷酸多态性芯片（Single Nucleotide Polymorphism array, SNP array）分析显示，该受累患儿的染色体区域既无缺失也无扩增；而包含130种已知耳聋相关基因的靶向基因富集检测组合未检出致病性突变（pathogenic mutations）。斑马鱼（zebrafish）与人类体内的基因表达模式均未证实ATE1与SLC12A1基因具有耳特异性功能。对该患儿及180例GJB2突变阴性的听力受损个体的这2个基因进行桑格测序（Sanger sequencing），未检出纯合（homozygous）或复合杂合（compound heterozygous）致病性突变。本研究揭示了解析异质性表型分子病因过程中所面临的诸多难题。我们无法直接将ATE1和/或SLC12A1基因的断裂与该异常听力表型建立关联；不过，这些基因的突变可能在多基因（polygenic）及多因素（multifactorial）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迄今尚未被发现的耳聋相关基因中的致病突变。显然，仅ATE1和/或SLC12A1基因功能的断裂并不会产生不良影响。