Branchio-oto-renal Research Articles

A family affected by branchio-oto syndrome with EYA1 mutations

Branchio-oto (BO) syndrome is complicated with congenital preauricular fistulae, branchial fistulae (cysts), and hearing loss (sensorineural, conductive or mixed). As well as branchio-oto-renal (BOR) syndrome, it is known to be an autosomal dominant hereditary disorder. Since mutations in the EYA1 gene have been identified in both BO and BOR syndromes, mutation screening of this gene has been drawing attention as a genetic test to diagnose BOR/BO syndromes. In this study, we genetically investigated the presence of EYA1 mutations in a BO syndrome family in which we observed congenital preauricular fistulae, branchial fistulae (cysts) and hearing loss in four generations. Whereas there was a variety of phenotype expressions in this family, all subjects tested had a nonsense mutation (R264X) in exon 8 of the EYA1 gene. The present report adds further examples to support the usefulness of molecular genetic testing for the diagnosis of patients with BO syndrome.

Branchio-oto-renal syndrome: A report on nine family groups

This study reviews nine new families with branchio-oto-renal (BOR) syndrome (Online Mendelian Inheritance in Man [OMIM] 113650). Diagnosis was made by studying 10 index cases, and then 22 other previously undetected patients were diagnosed within the nine families. The syndrome consists of conductive, sensorineural, or mixed hearing loss; preauricular pits; structural defects of the outer, middle, or inner ear; renal anomalies; lateral cervical fistulas, cysts, or sinuses; and/or nasolacrimal duct stenosis or fistulas. In our study, all patients first diagnosed in each familial group were recognized on the basis of severe renal anomalies associated with at least one of these symptoms. Our study showed that BOR syndrome is a misdiagnosed disorder, usually recognized in the presence of severe renal failure but often not diagnosed, especially in the adult in the presence of other isolated clinical signs, such as mild branchial or urological anomalies. We stress the meticulous search we performed for renal anomalies and/or hearing loss in all subjects showing minimal signs of branchial defects. BOR syndrome should be suspected in all cases of isolated urological anomalies, even if no other signs of the syndrome are present. After BOR syndrome has been diagnosed in a patient, all family members should be examined for the presence of the syndrome, even if there are only minimal stigmata of the disease.

Branchio-oto-renal syndrome: A report on nine family groups

This study reviews nine new families with branchio-oto-renal (BOR) syndrome (Online Mendelian Inheritance in Man [OMIM] 113650). Diagnosis was made by studying 10 index cases, and then 22 other previously undetected patients were diagnosed within the nine families. The syndrome consists of conductive, sensorineural, or mixed hearing loss; preauricular pits; structural defects of the outer, middle, or inner ear; renal anomalies; lateral cervical fistulas, cysts, or sinuses; and/or nasolacrimal duct stenosis or fistulas. In our study, all patients first diagnosed in each familial group were recognized on the basis of severe renal anomalies associated with at least one of these symptoms. Our study showed that BOR syndrome is a misdiagnosed disorder, usually recognized in the presence of severe renal failure but often not diagnosed, especially in the adult in the presence of other isolated clinical signs, such as mild branchial or urological anomalies. We stress the meticulous search we performed for renal anomalies and/or hearing loss in all subjects showing minimal signs of branchial defects. BOR syndrome should be suspected in all cases of isolated urological anomalies, even if no other signs of the syndrome are present. After BOR syndrome has been diagnosed in a patient, all family members should be examined for the presence of the syndrome, even if there are only minimal stigmata of the disease.

Genomewide Search and Genetic Localization of a Second Gene Associated with Autosomal Dominant Branchio-Oto-Renal Syndrome: Clinical and Genetic Implications

Branchio-oto-renal (BOR) syndrome is characterized by ear malformations, cervical fistulas, hearing loss, and renal anomalies. It is an autosomal dominant disorder with variable clinical manifestations. The most common features of BOR syndrome are branchial, hearing, and renal anomalies. However, many affected subjects have been observed with branchial-cleft anomalies and hearing loss but without renal anomalies, a condition called "branchio-otic" (BO) syndrome. It is logical to question whether the BOR and BO syndromes are allelic or whether they represent distinct genetic entities. We identified a very large extended family whose members had branchial and hearing anomalies associated with commissural lip pits that segregated in an autosomal dominant fashion. Using a genomewide search strategy, we identified genetic linkage, with a maximum LOD score of 4.81 at recombination fraction 0, between the BO phenotype and polymorphic marker D1S2757 in the genetic region of chromosome 1q31. This is the first report of linkage for a second gene associated with BOR syndrome. The findings have important clinical implications and will provide insight into the genetic basis of BOR syndrome.

Exclusion of the branchio-oto-renal syndrome locus (EYA1) from patients with branchio-oculo-facial syndrome.

In addition to craniofacial, auricular, ophthalmologic, and oral anomalies, the distinctive phenotype of the branchio-oculo-facial (BOF) syndrome (MIM 113620) includes skin defects in the neck or infra/supra-auricular region. These unusual areas of thin, erythematous wrinkled skin differ from the discrete cervical pits, cysts, and fistulas of the branchio-oto-renal (BOR) syndrome (MIM 113650). Although the BOF and BOR syndromes are sufficiently distinctive that they should not be confused, both can be associated with nasolacrimal duct stenosis, deafness, prehelical pits, malformed pinna, and renal anomalies. Furthermore, a reported father and son [Legius et al., 1990, Clin Genet 37:347-500] had features of both conditions. It was not clear whether they had an atypical presentation of either BOR or BOF syndrome, or represented a private syndrome. In light of these issues, we selected the BOR locus (EYA1) as a possible gene mutation for the BOF syndrome. In five BOF patients, there were no mutations detected in the EYA1 gene, suggesting that it is not allelic to the BOR syndrome.

Mutations of a human homologue of the Drosophila eyes absent gene (EYA1) detected in patients with congenital cataracts and ocular anterior segment anomalies.

The Drosophila eyes absent gene ( eya ) is involved in the formation of compound eyes. Flies with loss-of-function mutations of this gene develop no eyes and form the ectopic eye in the antennae and the ventral zone of the head on target expression. A highly conserved homo-logous gene in various invertebrates and vertebrates has been shown to function in the formation of the eye. In contrast, a human homologue, EYA1, has been identified by positional cloning as a candidate gene for branchio-oto-renal (BOR) syndrome, in which phenotypic manifestations are restricted to the areas of branchial arch, ear and kidney, with usually no anomalies in the eye. We have examined genomic DNA isolated from patients with various types of developmental eye anomaly for EYA1 mutations by the use of polymerase chain reaction-single-strand conformation polymorphism and sequencing. We identified three novel missense mutations in patients who had con-genital cataracts and ocular anterior segment anomalies. One of the patients had clinical features of BOR syndrome as well. This result implies that the human EYA1 gene is also involved in eye morphogenesis, and that a wide variety of clinical manifestations may be caused by EYA1 mutations.

Eya1-deficient mice lack ears and kidneys and show abnormal apoptosis of organ primordia.

Haploinsufficiency for human EYA1, a homologue of the Drosophila melanogaster gene eyes absent (eya), results in the dominantly inherited disorders branchio-oto-renal (BOR) syndrome and branchio-oto (BO) syndrome, which are characterized by craniofacial abnormalities and hearing loss with (BOR) or without (BO) kidney defects. To understand the developmental pathogenesis of organs affected in these syndromes, we inactivated the gene Eya1 in mice. Eya1 heterozygotes show renal abnormalities and a conductive hearing loss similar to BOR syndrome, whereas Eya1 homozygotes lack ears and kidneys due to defective inductive tissue interactions and apoptotic regression of the organ primordia. Inner ear development in Eya1 homozygotes arrests at the otic vesicle stage and all components of the inner ear and specific cranial sensory ganglia fail to form. In the kidney, Eya1 homozygosity results in an absence of ureteric bud outgrowth and a subsequent failure of metanephric induction. Gdnf expression, which is required to direct ureteric bud outgrowth via activation of the c-ret Rtk (refs 5, 6, 7, 8), is not detected in Eya1-/- metanephric mesenchyme. In Eya1-/- ear and kidney development, Six but not Pax expression is Eya1 dependent, similar to a genetic pathway elucidated in the Drosophila eye imaginal disc. Our results indicate that Eya1 controls critical early inductive signalling events involved in ear and kidney formation and integrate Eya1 into the genetic regulatory cascade controlling kidney formation upstream of Gdnf. In addition, our results suggest that an evolutionarily conserved Pax-Eya-Six regulatory hierarchy is used in mammalian ear and kidney development.

EYA1 nonsense mutation in a Japanese branchio-oto-renal syndrome family

Advances in molecular genetics have recently revealed that mutations in the EYA1 gene are responsible for branchio-oto-renal (BOR) syndrome in European and other populations. This is the first report confirming that an EYA1 gene mutation is also disease-causing in an Asian population. We have described one Japanese BOR syndrome family showing a novel mutation in exon 7 of the EYA1 gene. There was extensive variation of clinical phenotypes within this family. When the physician is confronted with a BOR family showing a wide variation in clinical expression, molecular genetic testing helps to achieve accurate diagnosis.

Inner ear and kidney anomalies caused by IAP insertion in an intron of the Eya1 gene in a mouse model of BOR syndrome.

A spontaneous mutation causing deafness and circling behavior was discovered in a C3H/HeJ colony of mice at the Jackson Laboratory. Pathological analysis of mutant mice revealed gross morphological abnormalities of the inner ear, and also dysmorphic or missing kidneys. The deafness and abnormal behavior were shown to be inherited as an autosomal recessive trait and mapped to mouse chromosome 1 near the position of the Eya1 gene. The human homolog of this gene, EYA1, has been shown to underly branchio-oto-renal (BOR) syndrome, an autosomal dominant disorder characterized by hearing loss with associated branchial and renal anomalies. Molecular analysis of the Eya1 gene in mutant mice revealed the insertion of an intracisternal A particle (IAP) element in intron 7. The presence of the IAP insertion was associated with reduced expression of the normal Eya1 message and formation of additional aberrant transcripts. The hypomorphic nature of the mutation may explain its recessive inheritance, if protein levels in homozygotes, but not heterozygotes, are below a critical threshold needed for normal developmental function. The new mouse mutation is designated Eya1(bor) to denote its similarity to human BOR syndrome, and will provide a valuable model for studying mutant gene expression and etiology.

Human NDUFB9 Gene: Genomic Organization and a Possible Candidate Gene Associated with Deafness Disorder Mapped to Chromosome 8q13

Human NADH dehydrogenase (ubiquinone) 1β-subcomplex, 9 (NDUFB9) is a nuclear encoded mitochondrial protein with the respiratory electron transport chain. It has been physically mapped to a 1-Mb deletion at chromosome 8q13 which also contains the gene for branchio-oto-renal (BOR) syndrome. BOR syndrome is characterized by branchial and renal abnormalities with hearing impairment. Since several hereditary deafness disorders have been associated with mitochondrial mutations, NDUFB9 was considered a candidate gene for BOR syndrome. Recently, EYA1 gene has been identified in the region which underlies the BOR syndrome but majority of BOR families did not show mutations in the EYA1 gene. Here we have determined the genomic structure of the NDUFB9 gene, including the nucleotide sequence, organization and the boundaries of the four coding exons. PCR primers were designed from the adjacent intron sequences that allow amplification of the four exons that encode the complete open reading frame. To identify whether mutations in NDUFB9 are involved in causing the BOR syndrome, we screened 9 BOR families which did not show mutations in the EYA1 gene by heteroduplex analysis; however, no mutations were found.

Eya1 expression in the developing ear and kidney: towards the understanding of the pathogenesis of Branchio-Oto-Renal (BOR) syndrome.

Branchio-Oto-Renal (BOR) syndrome is an autosomal dominant, early developmental defect characterised by varying combinations of branchial (fistulas, sinuses, and cysts), outer, middle and inner ear, and renal anomalies. The gene underlying this syndrome, EYA1, is homologous to the Drosophila developmental gene eyes absent which encodes a transcriptional co-activator required for eye specification. We report here the temporal and spatial pattern of expression of the murine homologue, Eya1, throughout ear and kidney development in relation to the anomalies of BOR syndrome. The expression of Eya1 in the branchial arch apparatus (namely in the 2nd, 3rd, and 4th branchial clefts and pharyngeal pouches) at embryonic day (E)10.5, can be correlated with the branchial fistulas, sinuses, and cysts but not with the outer and middle ear anomalies. In contrast, Eya1 is expressed during the slightly more advanced stage of outer and middle ear morphogenesis at E13.5, in the mesenchyme adjacent to the first branchial cleft (the cleft will give rise to the external auditory canal and the surrounding mesenchyme to the auricular hillocks) and surrounding the primordia of the middle ear ossicles, and in the epithelium of the tubotympanic recess (the future tympanic cavity). During early inner ear development, Eya1 is expressed in the ventromedial wall of the otic vesicle (the site of the future sensory epithelia), in the statoacoustic ganglion, and in the periotic mesenchyme, consistent with the cochlear anomalies and sensorineural hearing loss of BOR syndrome. Subsequently, Eya1 expression is observed in the differentiating hair and supporting cells of the sensory epithelia, as well as in the associated ganglia, and persists after differentiation has taken place. This suggests that, in addition to a role in the morphogenetic process, Eya1 could also be implicated in the differentiation and/or survival of these inner ear cell populations. Finally, Eya1 expression in the condensing mesenchymal cells of the kidney is consistent with the excretory and collecting system anomalies of BOR syndrome. From the comparison of the Eya1 and Pax2 expression patterns during ear and kidney development, a contribution of these two genes to the same regulatory pathway can only be suggested in the mesenchymal-epithelial transition directing renal tubule formation.

Description of a large kindred with autosomal dominant inheritance of branchial arch anomalies, hearing loss, and ear pits, and exclusion of the branchio‐oto‐renal (BOR) syndrome gene locus (chromosome 8q13.3)

It has been suggested that branchio-oculo-facial (BOF) syndrome, deafness with ear pits, and associated conditions [MIM nos. 125100, 120502], and branchio-oto-renal (BOR) [MIM no. 113650] or Melnick-Fraser syndrome represent phenotypic variants of the BOR syndrome, which is inherited in an autosomal dominant (AD) manner and has variable clinical expression. Recently, the BOR gene was mapped to chromosome region 8q13.3 and its sequence was identified as the human homolog of the Drosophila eyes absent (EYA1) gene. We studied an extended family with AD inheritance of branchial arch anomalies (BAA), hearing loss, and ear pits, whose phenotype differed from that of patients with BOR in that none of the affected members had renal abnormalities or lacrimal duct stenosis. Fifteen affected members were studied; ear pits were present in all of them, whereas hearing loss and other BAA were present in 40 and 20%, respectively. Blood was collected from 31 patients; DNA was extracted by standard methods and amplified using primers from microsatellite sequences flanking the BOR locus on chromosome 8q13.3 (D8S1807, D8S530, and D8S543). Linkage analysis was performed under two models of AD inheritance with different penetrance: 100% and 80%. In both cases, the logarithm of odds(LOD) scores produced were significantly less than −2; exclusion of the 8q13.3 locus was also confirmed by multipoint LOD score analysis. We conclude that, in one large family with AD inheritance of BAA, hearing loss and ear pits, the BOR locus was excluded. This represents the first documentation of heterogeneity in branchio-oto anomalies, syndromes with phenotypes similar to BOR syndrome. Am. J. Med. Genet. 79:209–214, 1998. © 1998 Wiley-Liss, Inc.

Description of a large kindred with autosomal dominant inheritance of branchial arch anomalies, hearing loss, and ear pits, and exclusion of the branchio-oto-renal (BOR) syndrome gene locus (chromosome 8q13.3)

It has been suggested that branchio-oculo-facial (BOF) syndrome, deafness with ear pits, and associated conditions [MIM nos. 125100, 120502], and branchio-oto-renal (BOR) [MIM no. 113650] or Melnick-Fraser syndrome represent phenotypic variants of the BOR syndrome, which is inherited in an autosomal dominant (AD) manner and has variable clinical expression. Recently, the BOR gene was mapped to chromosome region 8q13.3 and its sequence was identified as the human homolog of the Drosophila eyes absent (EYA1) gene. We studied an extended family with AD inheritance of branchial arch anomalies (BAA), hearing loss, and ear pits, whose phenotype differed from that of patients with BOR in that none of the affected members had renal abnormalities or lacrimal duct stenosis. Fifteen affected members were studied; ear pits were present in all of them, whereas hearing loss and other BAA were present in 40 and 20%, respectively. Blood was collected from 31 patients; DNA was extracted by standard methods and amplified using primers from microsatellite sequences flanking the BOR locus on chromosome 8q13.3 (D8S1807, D8S530, and D8S543). Linkage analysis was performed under two models of AD inheritance with different penetrance: 100% and 80%. In both cases, the logarithm of odds (LOD) scores produced were significantly less than -2; exclusion of the 8q13.3 locus was also confirmed by multipoint LOD score analysis. We conclude that, in one large family with AD inheritance of BAA, hearing loss and ear pits, the BOR locus was excluded. This represents the first documentation of heterogeneity in branchio-oto anomalies, syndromes with phenotypes similar to BOR syndrome.

Branchio-oto-renal syndrome

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder with branchial, otologic, and renal manifestations. The branchial manifestations usually are inconsequential, however the hearing impairment and renal malformations can be significant. The disease is caused by mutations in the EYA1 gene.

Renal failure and deafness: Branchio-oto-renal syndrome

Branchio-oto-renal (BOR) syndrome is a rare autosomal dominant condition that may present with hearing loss, branchial cysts, and renal failure. The characteristic phenotypic expression of the full syndrome may be partial or complete, and a whole range of renal abnormalities may be present. Its similarity to Alport's syndrome may lead to misdiagnosis. We report here a case of adult-onset renal failure in a 44-year-old white man previously believed to have Alport's syndrome and a review the relevant literature. (Am J Kidney Dis 1998 Aug;32(2):334-7)

Identification of three novel mutations in human EYA1 protein associated with branchio-oto-renal syndrome.

The Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder characterized by branchial clefts, preauricular sinuses, hearing loss, and renal anomalies. Recent studies have shown that mutations in EYA1 are associated with BOR. However, the underlying molecular mechanisms by which mutations in the EYA1 gene cause BOR syndrome are unknown. We have investigated 12 unrelated Caucasian families for mutations by heteroduplex analysis and direct sequencing of products from the polymerase chain reaction. In this study, we identified two novel frameshift deletions and a single base substitution that introduces a stop codon mutation in the C-terminal region of the EYA1 gene. No obvious relationships were observed between the nature of the mutations and the variable clinical features associated with BOR syndrome.

Identification of three novel mutations in human EYA1 protein associated with branchio‐oto‐renal syndrome

The Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder characterized by branchial clefts, preauricular sinuses, hearing loss, and renal anomalies. Recent studies have shown that mutations in EYA1 are associated with BOR. However, the underlying molecular mechanisms by which mutations in the EYA1 gene cause BOR syndrome are unknown. We have investigated 12 unrelated Caucasian families for mutations by heteroduplex analysis and direct sequencing of products from the polymerase chain reaction. In this study, we identified two novel frameshift deletions and a single base substitution that introduces a stop codon mutation in the C-terminal region of the EYA1 gene. No obvious relationships were observed between the nature of the mutations and the variable clinical features associated with BOR syndrome. Hum Mutat 11:443–449, 1998. © 1998 Wiley-Liss, Inc.

Clustering of mutations responsible for branchio-oto-renal (BOR) syndrome in the eyes absent homologous region (eyaHR) of EYA1.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder, characterised by the association of branchial, otic and renal anomalies with variable degrees of severity. We have recently identified EYA1 , a human homologue of the Drosophila eyes absent gene, as the gene underlying this syndrome. The products of both genes share a highly conserved 271 amino acid C-terminal region (eyaHR). The eyaHR was also found in the products of two other human genes (EYA2 and EYA3), demonstrating the existence of a novel gene family. We report here on the complete genomic structure of EYA1. This gene consists of 16 coding exons and extends over 156 kb. It encodes various alternatively spliced transcripts differing only in their 5' regions. Sequence analysis of the entire EYA1 coding region was performed for 20 unrelated patients affected by BOR syndrome, and six novel mutations were identified. Among these mutations, two are missense mutations, highlighting amino acid residues essential for the function of the EYA1 protein, and one mutation comprises a de novo Alu insertion into an exon. This insertion presumably occurs by retrotransposition, and the mobile Alu element has a poly(A) tail that is unstable throughout generations. To date, 14 mutations have been detected in BOR patients, all of which are different. However, all the mutations are located within or in the immediate vicinity of the eyaHR; the significance of this clustering is discussed.

The Human B22 Subunit of the NADH-Ubiquinone Oxidoreductase Maps to the Region of Chromosome 8 Involved in Branchio-Oto-Renal Syndrome

To identify candidate genes for Branchio-oto-renal (BOR) syndrome, we have made use of a set of cosmids that map to 8q13.3, which has previously been shown to be involved in this syndrome. These cosmids were used as genomic clones in the attempts to isolate corresponding cDNAs using a modified hybrid selection technique. cDNAs from the region were identified and used to search for sequence similarity in human or other species. One cDNA clone was found to have 89% sequence similarity to the bovine B22 subunit of NADH-ubiquinone oxidoreductase, a mitochondrial protein in the respiratory electron transport chain. Given the history of other mitochondrial mutations being involved in hearing loss syndromes, this gene should be considered a strong candidate for involvement in BOR.

Characterization of a Translocation-Associated Deletion Defines the Candidate Region for the Gene Responsible for Branchio-Oto-Renal Syndrome

Fluorescencein situhybridization analysis of an 8q translocation breakpoint, dir ins(8)(q24.11;q13.3;q21.13), carried by an individual presenting with Branchio-Oto-Renal (BOR) syndrome, resulted in the identification of an associated deletion. The generation of a YAC contig and the isolation of overlapping recombinant P1 and λ phage clones from the region allowed further characterization of this deletion. Its size was estimated to be between 470 and 650 kb, and it was flanked by the two polymorphic markers D8S1060 and D8S1807. This mapping led us to reevaluate the localization of the gene responsible for BOR syndrome and has now focused the search for the BOR gene to within the limits of this deletion.