Letters to the Editor

Prenatal diagnosis and genetic analysis of a fetus with Branchio-oto-renal syndrome: A case report

BACKGROUND

Branchio-oto-renal (BOR) syndrome is an autosomal-dominant disorder characterized by branchial arch anomalies, hearing loss, and kidney defects. Mutations in the human EYA1 gene have been reported associated with BOR syndrome. Here we identified that a novel variant, EYA1: NM_000503.4: c.827-1G > C (Intron 8, shear mutation) was associated with BOR in a fetus of a Chinese family.

CASE PRESENTATION

Prenatal ultrasound examination showed that both kidneys of the fetus were small and the echo of both kidneys was enhanced. The amount of amniotic fluid was normal, and no other structural abnormalities of the fetus were found. Fetal umbilical cord blood puncture was performed. No abnormality was found in karyotyping and chromosomal microarray analysis (CMA) results. Thus, we performed a trio-based whole exome sequencing (WES), and found that the fetus carried a novel homozygous variant, EYA1: NM_000503.4: c.827-1G > C (Intron 8, shear mutation), but the parents do not have this mutation. The variation sites of fetus and parents were verified by Sanger sequencing to clarify the source of pathogenic variation.

CONCLUSION

Combined with fetal imaging examination, the novel variation of EYA1: NM_000503.4: c.827-1G > C is the cause of fetal renal dysplasia. This case report indicates that the early use of appropriate technology can clarify the etiology of fetal disease and guide prognosis consultation.

Otological manifestations in branchiootorenal spectrum disorder: A systematic review and meta-analysis

Branchiootorenal spectrum disorder (BORSD) is a group of rare autosomal dominant entities characterized by branchiogenic malformations, hearing loss (HL) and renal anomalies. It comprises branchiootorenal syndrome and branchiootic syndrome, distinguished by the presence or absence of renal abnormalities. Pathogenic variants have been discovered in the following genes: EYA1, SIX5, SIX1 and SALL1. As the otological phenotype in BORSD is inconsistently reported, we performed a systematic review to provide an up-to-date overview, correlated with the genotype. Forty publications were included, describing 295 individual patients. HL was diagnosed in 95%, usually bilateral and mixed-type, and differed among the different genes involved. Mixed moderate-to-severe HL was the predominant finding in patients with EYA1 involvement, regardless of the presence of renal abnormalities. The sensorineural HL of profound severity was more prevalent in patients with SIX1 mutations. No significant differences among different mutation types or location within the genes could be observed. Structural otological manifestations, ranging from periauricular to inner ear anomalies, were common in both genes. Especially periauricular anomalies were more common and more severe in EYA1. In summary, otological differences among the different genes involved in BORSD are observed, so the molecular analysis is strongly advised.

A novel mutation in EYA1 in a Chinese family with Branchio-oto-renal syndrome

Background

Branchio-oto-renal (BOR) syndrome is a dominant autosomal disorder characterized by phenotypes such as hearing loss, branchial fistulae, preauricular pits, and renal abnormalities. EYA1, the human homolog of the Drosophila “eye absent” gene on chromosome 8q13.3, is recognized as one of the most important genes associated with BOR syndrome.

Methods

The proposita in this study was a 5-year-old Chinese girl with hearing loss, bilateral otitis media with effusion, microtia, facial hypoplasia, palatoschisis, and bilateral branchial cleft fistulae. The girl’s family members, except two who were deceased, agreed to undergo clinical examination. We collected blood samples from 10 family members, including six who were affected by the syndrome. Genomic DNA was extracted and subjected to Sanger sequencing. A minigene assay was performed to confirm whether splicing signals were altered. In addition, we performed western blotting to determine alterations in protein levels of the wild-type and mutant gene.

Results

Clinical tests showed that some of the family members met the criteria for BOR syndrome. The affected members harbored a novel heterozygous nonsense variation in exon 11 of EYA1, whereas no unaffected member carried the mutation at this position. Functional experiments did not detect abnormal splicing at the RNA level; however, western blotting showed that the mutated protein was truncated.

Conclusions

This study reports a novel mutation associated with BOR syndrome in a Chinese family. We highlight the usefulness of genetic testing in the diagnosis of BOR syndrome. Thus, we believe that this report would benefit clinicians in this field.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0653-2) contains supplementary material, which is available to authorized users.

Genetic syndromes involving hearing

OBJECTIVE

The fundamental processes involved in the mechanism of hearing seem to be controlled by hundreds of genes and hereditary hearing impairment may be caused by a large variety of genetic mutations in different genes. Approximately 150 loci for monogenic syndromic and non-syndromic hearing impairment (HI) disorders have been mapped to the human genome. The identification of these genes and functional analysis of the proteins they encode, are paving the way towards a better understanding of the physiology and pathophysiology of the auditory system. To date, approximately 50 causative genes have been identified.

METHODS

The clinical and neuroradioldical findings of syndromal hearing impairment are analysed.

RESULTS

This paper presents an updated report on genetic syndromes in which a hearing impairment is involved, with a particular attention to the ones associated with external ear and craniofacial malformations.

CONCLUSIONS

Concepts in human genetics are rapidly evolving together with technologies. The concept itself of gene is changing. A genetic diagnosis of syndromal hearing impairment has many practical consequences: it can implies specific prognosis, specific management, specific recurrence risk in relatives and, if the diagnosis is confirmed at the molecular level, possibility of a specific early prenatal diagnosis for severe syndromes. It is important to highlight the necessity that the pediatric otolaryngologist must have a close collaboration with a clinical geneticist and a neuroradiologist.

Crystal structure of ED-Eya2: insight into dual roles as a protein tyrosine phosphatase and a transcription factor

Eya proteins are transcription factors that play pivotal roles in organ formation during development by mediating interactions between Sine Oculis (SO) and Dachshund (DAC). Remarkably, the transcriptional activity of Eya proteins is regulated by a dephosphorylating activity within its Eya domain (ED). However, the molecular basis for the link between catalytic and transcriptional activities remains unclear. Here we report the first description of the crystal structure of the ED of human Eya2 (ED-Eya2), determined at 2.4-A resolution. In stark contrast to other members of the haloacid dehalogenase (HAD) family to which ED-Eya2 belongs, the helix-bundle motif (HBM) is elongated along the back of the catalytic site. This not only results in a structure that accommodates large protein substrates but also positions the catalytic and the SO-interacting sites on opposite faces, which suggests that SO binding is not directly affected by catalytic function. Based on the observation that the DAC-binding site is located between the catalytic core and SO binding sites within ED-Eya2, we propose that catalytic activity can be translated to SO binding through DAC, which acts as a transcriptional switch. We also captured at two stages of reaction cycles-acyl-phosphate intermediate and transition state of hydrolysis step, which provided a detailed view of reaction mechanism. The ED-Eya2 structure defined here serves as a model for other members of the Eya family and provides a framework for understanding the role of Eya phosphatase mutations in disease.

A recurrent EYA1 mutation causing alternative RNA splicing in branchio-oto-renal syndrome: implications for molecular diagnostics and disease mechanism

Branchio-oto-renal syndrome is a heterogeneous disorder inherited in an autosomal dominant pattern, characterized by branchial arch abnormalities, hearing loss and renal abnormalities, with mutations in EYA1 reported in 30-70% of patients. We have applied a molecular testing strategy of sequencing of the complete coding region/flanking intronic regions and multiple ligation probe amplification analysis of EYA1 to a pediatric branchio-oto-renal proband cohort. EYA1 mutations were identified in 82% (14/17) of the probands. We also describe a novel recurrent EYA1 mutation c.867 + 5G > A found in five unrelated affected patients. RNA analysis showed that c.867 + 5G > A affects EYA1 splicing, producing an aberrant mRNA transcript lacking exon 8 and resulting in premature termination in exon 9. The aberrant transcript was present at approximately 50% level of wild-type EYA1 mRNA in fibroblasts, and is predicted to encode an EYA1 protein retaining the amino terminal transcriptional coactivator region but lacking the conserved carboxy terminal Eya phosphatase domain. Patients with the c.867 + 5G > A mutation were found to have more severe renal abnormalities than probands with other mutations in this cohort. Analysis of the c.867 + 5G > A mutation suggests that certain transcripts of EYA1 escape nonsense-mediated decay and encode truncated EYA proteins that may be capable of dominant-negative interactions producing distinct phenotypic features within the branchio-oto-renal spectrum.

Branchio-oto-renal syndrome: detection of EYA1 and SIX1 mutations in five out of six Danish families by combining linkage, MLPA and sequencing analyses

The branchio-oto-renal (BOR) syndrome is an autosomal-dominant disorder characterized by hearing loss, branchial and renal anomalies. BOR is genetically heterogeneous and caused by mutations in EYA1 (8q13.3), SIX1 (14q23.1), SIX5 (19q13.3) and in an unidentified gene on 1q31. We examined six Danish families with BOR syndrome by assessing linkage to BOR loci, by performing EYA1 multiplex ligation-dependent probe amplification (MLPA) analysis for deletions and duplications and by sequencing of EYA1, SIX1 and SIX5. We identified four EYA1 mutations (c.920delG, IVS10-1G>A, IVS12+4A>G and p.Y591X) and one SIX1 mutation (p.W122R), providing a molecular diagnosis in five out of the six families (83%). The present, yet preliminary, observation that renal and temporal bone malformations are less frequent in SIX1-related disease suggests a slightly different clinical profile compared to EYA1-related disease. Unidentified mutations impairing mRNA expression or further genetic heterogeneity may explain the lack of mutation finding in one family despite LOD score indications of EYA1 involvement.