title: Branchio-otic syndrome caused by a genomic rearrangement: clinical findings and molecular cytogenetic studies in a patient with a pericentric inversion of chromosome 8.
abstract: Branchio-oto-renal (BOR) syndrome is an autosomal dominantly inherited developmental disorder, which is characterized by anomalies of the ears, the branchial arches and the kidneys. It is caused by mutations in the genes EYA1,SIX1 and SIX5. Genomic rearrangements of chromosome 8 affecting the EYA1 gene have also been described. Owing to this fact, methods for the identification of abnormal copy numbers such as multiplex ligation-dependent probe amplification (MLPA) have been introduced as routine laboratory techniques for molecular diagnostics of BOR syndrome. The advantages of these techniques are clear compared to standard cytogenetic and array approaches as well as Southern blot. MLPA detects deletions or duplications of a part or the entire gene of interest, but not balanced structural aberrations such as inversions and translocations. Consequently, disruption of a gene by a genomic rearrangement may escape detection by a molecular genetic analysis, although this gene interruption results in haploinsufficiency and, therefore, causes the disease. In a patient with clinical features of BOR syndrome, such as hearing loss, preauricular fistulas and facial dysmorphisms, but no renal anomalies, neither sequencing of the 3 genes linked to BOR syndrome nor array comparative genomic hybridization and MLPA were able to uncover a causative mutation. By routine cytogenetic analysis, we finally identified a pericentric inversion of chromosome 8 in the affected female. High-resolution multicolor banding confirmed the chromosome 8 inversion and narrowed down the karyotype to 46,XX,inv(8)(p22q13). By applying fluorescence in situ hybridization, we narrowed down both breakpoints on chromosome 8 and found the EYA1 gene in q13.3 to be directly disrupted. We conclude that standard karyotyping should not be neglected in the genetic diagnostics of BOR syndrome or other Mendelian disorders, particularly when molecular testing failed to detect any causative alteration in patients with a convincing phenotype.
authors.affiliation: Institute of Human Genetics, University of Göttingen, Göttingen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Schmidt
authors.forename: T
authors.initials: T
authors.lastname: Bierhals
authors.forename: F
authors.initials: F
authors.lastname: Kortüm
authors.forename: I
authors.initials: I
authors.lastname: Bartels
authors.forename: T
authors.initials: T
authors.lastname: Liehr
authors.forename: P
authors.initials: P
authors.lastname: Burfeind
authors.forename: M
authors.initials: M
authors.lastname: Shoukier
authors.forename: V
authors.initials: V
authors.lastname: Frank
authors.forename: C
authors.initials: C
authors.lastname: Bergmann
authors.forename: K
authors.initials: K
authors.lastname: Kutsche
mesh_terms: D000328:Adult; D019280:Branchio-Oto-Renal Syndrome / Q000235:genetics* / Q000473:pathology; D056905:Chromosome Breakpoints; D007446:Chromosome Inversion; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics / Q000648:ultrastructure*; D055028:Comparative Genomic Hybridization; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000209:etiology; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics*; D060885:Multiplex Polymerase Chain Reaction; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics*; D010641:Phenotype; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics*
chemical_list: D018398:Homeodomain Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; C099236:SIX1 protein, human; C106687:SIX5 protein, human; C104381:EYA1 protein, human; D017027:Protein Tyrosine Phosphatases