Genetic research progress in branchio-oto syndrome/ branchio-oto-renal syndrome / 中南大学学报(医学版)

Branchio-oto syndrome (BOS)/branchio-oto-renal syndrome (BORS) is a kind of autosomal dominant heterogeneous disorder. These diseases are mainly characterized by hearing impairment and abnormal phenotype of ears, accompanied by renal malformation and branchial cleft anomalies including cyst or fistula, with an incidence of 1/40 000 in human population. Otic anormalies are one of the most obvious clinical manifestations of BOS/BORS, including deformities of external, middle, inner ears and hearing loss with conductive, sensorineural or mix, ranging from mild to profound loss. Temporal bone imaging could assist in the diagnosis of middle ear and inner ear malformations for clinicians. Multiple methods including direct sequencing combined with next generation sequencing (NGS), multiplex ligation-dependent probe amplification (MLPA), or array-based comparative genomic hybridization (aCGH) can effectively screen and identify pathogenic genes and/or variation types of BOS/BORS. About 40% of patients with BOS/BORS carry aberrations of EYA1 gene which is the most important cause of BOS/BORS. A total of 240 kinds of pathogenic variations of EYA1 have been reported in different populations so far, including frameshift, nonsense, missense, aberrant splicing, deletion and complex rearrangements. Human Endogenous Retroviral sequences (HERVs) may play an important role in mediating EYA1 chromosomal fragment deletion mutations caused by non-allelic homologous recombination. EYA1 encodes a phosphatase-transactivator cooperated with transcription factors of SIX1, participates in cranial sensory neurogenesis and development of branchial arch-derived organs, then regulates the morphological and functional differentiation of the outer ear, middle ear and inner ear toward normal tissues. In addition, pathogenic mutations of SIX1 and SIX5 genes can also cause BOS/BORS. Variations of these genes mentioned above may cause disease by destroying the bindings between SIX1-EYA1, SIX5-EYA1 or SIX1-DNA. However, the role of SIX5 gene in the pathogenesis of BORS needs further verification.

Síndrome brânquio-otorrenal: um importante alerta / Branchio-oto-renal syndrome: an important warning

A síndrome brânquio-otorrenal (SBOR) é uma doença autossômica dominante, provocada por mutações em genes da organogênese humana, principalmente o gene EYA 1. Sua incidência é de 1 em 40.000 recém-nascidos vivos. As manifestações clínicas da SBOR decorrem de transtorno genético e envolvem perda auditiva de condução, neurossensorial ou mista, malformações da orelha externa, média e interna, cistos ou fístulas branquiais e anomalias renais que podem variar de hipoplasia a agenesia renal. O diagnóstico clínico da SBOR se baseia na presença de critérios clínicos. A genética molecular é de grande valor para a confirmação do diagnóstico e para estabelecer o diagnóstico pré-natal. Testes audiométricos completos e exames renais apurados são indicados a fim de mensurar com precisão a extensão dos danos causados pela doença. Sua ampla variabilidade clínica sugere, na literatura, que os diferentes fenótipos dessa síndrome representam, na realidade, grupos heterogêneos de doenças, que fazem diagnóstico diferencial, principalmente, com a síndrome brânquio-otorrenal. O tratamento se limita a reparar os danos causados pela doença, podendo estar indicado o uso de próteses auriculares ou intervenções cirúrgicas otológicas e renais, a fim de melhorar a qualidade de vida dos pacientes. O aconselhamento genético é a melhor forma de prevenção, sendo fundamental no tratamento.