Genome-wide copy number variation analysis of a Branchio-oto-renal syndrome cohort identifies a recombination hotspot and implicates new candidate genes

Genome-wide analysis of copy-number variation in humans with cleft lip and/or cleft palate identifies COBLL1, RIC1, and ARHGEF38 as clefting genes

Cleft lip with or without cleft palate (CL/P) is a common birth defect with a complex, heterogeneous etiology. It is well established that common and rare sequence variants contribute to the formation of CL/P, but the contribution of copy-number variants (CNVs) to cleft formation remains relatively understudied. To fill this knowledge gap, we conducted a large-scale comparative analysis of genome-wide CNV profiles of 869 individuals from the Philippines and 233 individuals of European ancestry with CL/P with three primary goals: first, to evaluate whether differences in CNV number, amount of genomic content, or amount of coding genomic content existed within clefting subtypes; second, to assess whether CNVs in our cohort overlapped with known Mendelian clefting loci; and third, to identify unestablished Mendelian clefting genes. Significant differences in CNVs across cleft types or in individuals with non-syndromic versus syndromic clefts were not observed; however, several CNVs in our cohort overlapped with known syndromic and non-syndromic Mendelian clefting loci. Moreover, employing a filtering strategy relying on population genetics data that rare variants are on the whole more deleterious than common variants, we identify several CNV-associated gene losses likely driving non-syndromic clefting phenotypes. By prioritizing genes deleted at a rare frequency across multiple individuals with clefts yet enriched in our cohort of individuals with clefts compared to control subjects, we identify COBLL1, RIC1, and ARHGEF38 as clefting genes. CRISPR-Cas9 mutagenesis of these genes in Xenopus laevis and Danio rerio yielded craniofacial dysmorphologies, including clefts analogous to those seen in human clefting disorders.

An infant with congenital heart defects and proteinuria: a case report

Background

Branchio-Oto-Renal (BOR) Syndrome is a rare autosomal disorder with a wide variety of clinical manifestations and a high degree of heterogeneity. Typical clinical manifestations of BOR syndrome include deafness, preauricular fistula, abnormal gill slits, and renal malformations. However, atypical phenotypes such as congenital hip dysplasia, congenital heart anomaly or facial nerve paresis are rare in BOR syndrome, and this might be easily misdiagnosed with other congenital disorders.

Case presentation

We report a 5-month-old boy of BOR syndrome with "congenital heart defects and proteinuria" as clinical features. Initially, as this case mainly presented with symptoms of recurrent respiratory infections and was found to be with congenital heart disease and proteinuria at the local hospital, but he only was diagnosed with congenital heart disease combined with pulmonary infection and anti-infective and supportive treatment was given. Subsequently, during the physical examination at our hospital, left side preauricular pit and branchial fistulae on the right neck were found. Subsequent evaluation of auditory brainstem response and distortion product otoacoustic emission were revealed sensorineural hearing impairment. Results of renal ultrasonography showed small kidneys. Genetic analysis revealed a microdeletion at chromosome 8q13.2-q13.3 encompassing EYA1 gene, this patient was finally diagnosed with BOR syndrome. Then, this patient received transcatheter patent ductus arteriosus closure and hearing aid treatment. Proteinuria, renal function and hearing ability are monitoring by nephrologist and otologist. The patient is currently being followed up until 3 months after discharge and his condition is stable.

Conclusion

Careful physical examination, detailed history and the implementation of diagnostic laboratory tests can reduce the incidence of misdiagnosis. Genetic sequencing analysis of patients is a key guide to the differential diagnosis of BOR syndrome.

From clinical to molecular diagnosis: relevance of diagnostic strategy in two cases of branchio-oto-renal syndrome - case report

Background

Branchio-oto-renal syndrome (BOR) is an autosomal dominant disorder characterized by deafness, branchiogenic malformations and renal abnormalities. Pathogenic variants in EYA1, SIX1 and SIX5 genes cause almost half of cases; copy number variants (CNV) and complex genomic rearrangements have been revealed in about 20% of patients, but they are not routinely and commonly included in the diagnostic work-up.

Case presentation

We report two unrelated patients with BOR syndrome clinical features, negative sequencing for BOR genes and the identification of a 2.65 Mb 8q13.2–13.3 microdeletion.

Conclusions

We highlight the value of CNV analyses in high level of suspicion for BOR syndrome but negative sequencing for BOR genes and we propose an innovative diagnostic flow-chart to increase current detection rate. Our report confirms a mechanism of non-allelic homologous recombination as causing this recurrent 8q13.2–13.3 microdeletion. Moreover, considering the role of PRDM14 and NCOA2 genes, both involved in regulation of fertility and deleted in our patients, we suggest the necessity of a longer follow-up to monitor fertility issues or additional clinical findings.

A Perihilar Variant of Focal Segmental Glomerulosclerosis Due to De novo Branchio-oto-renal Syndrome

Branchio-oto-renal syndrome is an autosomal dominant disorder characterized by branchial anomalies, hearing loss, and renal urinary tract malformations. We herein report a 32-year-old Japanese man with a right preauricular pit, bilateral mixed hearing loss, and malposition of the right kidney who presented with proteinuria. The findings of a left kidney biopsy were compatible with a perihilar variant of secondary focal segmental glomerular sclerosis. A trio exome analysis conducted among the patient and his parents failed to identify the causal gene variant, despite a sporadic pattern. His kidney function remained stable for 11 years with an angiotensin II receptor blocker.

A mutation of EYA1 gene in a Chinese Han family with Branchio-Oto syndrome

Branchio-Oto (BO) syndrome is one of the common syndromic forms of hearing loss. In this study, we aimed to characterize the clinical and genetic features of BO syndrome in a Chinese deaf family.The proposita in this study was a 29-years-old Chinese female with hearing loss, microtia, anterior concave auricle, and right branchial fistula. The family members agreed to undergo clinical examination. We collected blood samples from 7 family members, including 4 affected by the syndrome. Genomic DNA was extracted and subjected to Sanger sequencing. In addition, bioinformatics software SWISS MODEL was used to predict the protein encoded by EYA transcriptional coactivator and phosphatase 1 (EYA1) gene.Intra-familial consistency can be observed in the clinical phenotypes of BO syndrome in this family. EYA1 c.1627C>T (p.Gln543Ter) mutation was identified as the pathogenic cause in this family.This study reports a mutation associated with BO syndrome in a Chinese Han family. We highlight the utility of genetic testing in the diagnosis of BO syndrome. Thus, we believe that this report would provide a basis for the diagnosis of similar diseases in the future.

Identification and Characterization of a Cryptic Genomic Deletion-Insertion in EYA1 Associated with Branchio-Otic Syndrome

Branchio-oto-renal spectrum disorder (BORSD) is characterized by hearing loss accompanied by ear malformations, branchial cysts, and fistulae, with (branchio-oto-renal syndrome (BORS)) or without renal abnormalities (BOS (branchio-otic syndrome)). As the most common causative gene for BORSD, dominant mutations in EYA1 are responsible for approximately 40% of the cases. In a sporadic deaf patient diagnosed as BOS, we identified an apparent heterozygous genomic deletion spanning the first four coding exons and one 5′ noncoding exon of EYA1 by targeted next-generation sequencing of 406 known deafness genes. Real-time PCR at multiple regions of EYA1 confirmed the existence of this genomic deletion and extended its 5′ boundary beyond the 5′-UTR. Whole genome sequencing subsequently located the 5′ and 3′ breakpoints to 19268 bp upstream to the ATG initiation codon and 3180 bp downstream to exon 5. PCR amplification across the breakpoints in both the patient and his parents showed that the genomic alteration occurred de novo. Sanger sequencing of this PCR product revealed that it is in fact a GRCh38/hg38:chr8:g.71318554_71374171delinsTGCC genomic deletion-insertion. Our results showed that the genomic variant is responsible for the hearing loss associated with BOS and provided an example for deciphering such cryptic genomic alterations following pipelines of comprehensive exome/genome sequencing and designed verification.

A Missense Mutation in the KLF7 Gene Is a Potential Candidate Variant for Congenital Deafness in Australian Stumpy Tail Cattle Dogs

Congenital deafness is prevalent among modern dog breeds, including Australian Stumpy Tail Cattle Dogs (ASCD). However, in ASCD, no causative gene has been identified so far. Therefore, we performed a genome-wide association study (GWAS) and whole genome sequencing (WGS) of affected and normal individuals. For GWAS, 3 bilateral deaf ASCDs, 43 herding dogs, and one unaffected ASCD were used, resulting in 13 significantly associated loci on 6 chromosomes, i.e., CFA3, 8, 17, 23, 28, and 37. CFA37 harbored a region with the most significant association (−log₁₀(9.54 × 10⁻²¹) = 20.02) as well as 7 of the 13 associated loci. For whole genome sequencing, the same three affected ASCDs and one unaffected ASCD were used. The WGS data were compared with 722 canine controls and filtered for protein coding and non-synonymous variants, resulting in four missense variants present only in the affected dogs. Using effect prediction tools, two variants remained with predicted deleterious effects within the Heart development protein with EGF like domains 1 (HEG1) gene (NC_006615.3: g.28028412G>C; XP_022269716.1: p.His531Asp) and Kruppel-like factor 7 (KLF7) gene (NC_006619.3: g.15562684G>A; XP_022270984.1: p.Leu173Phe). Due to its function as a regulator in heart and vessel formation and cardiovascular development, HEG1 was excluded as a candidate gene. On the other hand, KLF7 plays a crucial role in the nervous system, is expressed in the otic placode, and is reported to be involved in inner ear development. 55 additional ASCD samples (28 deaf and 27 normal hearing dogs) were genotyped for the KLF7 variant, and the variant remained significantly associated with deafness in ASCD (p = 0.014). Furthermore, 24 dogs with heterozygous or homozygous mutations were detected, including 18 deaf dogs. The penetrance was calculated to be 0.75, which is in agreement with previous reports. In conclusion, KLF7 is a promising candidate gene causative for ASCD deafness.

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.

SHARPIN: Role in Finding NEMO and in Amyloid-Beta Clearance and Degradation (ABCD) Pathway in Alzheimer's Disease?

SHANK- associated RH domain-interacting protein (SHARPIN) is a multifunctional protein associated with numerous physiological functions and many diseases. The primary role of the protein as a LUBAC-dependent component in regulating the activation of the transcription factor NF-κB accounts to its role in inflammation and antiapoptosis. Hence, an alteration of SHARPIN expression or genetic mutations or polymorphisms leads to the alteration of the above-mentioned primary physiological functions contributing to inflammation-associated diseases and cancer, respectively. However, there are complications of targeting SHARPIN as a therapeutic approach, which arises from the wide-range of LUBAC-independent functions and yet unknown roles of SHARPIN including neuronal functions. The identification of SHARPIN as a postsynaptic protein and the emerging studies indicating its role in several neurodegenerative diseases including Alzheimer's disease suggests a strong role of SHARPIN in neuronal functioning. This review summarizes the functional roles of SHARPIN in normal physiology and disease pathogenesis and strongly suggests a need for concentrating more studies on identifying the unknown neuronal functions of SHARPIN and hence its role in neurodegenerative diseases.

Branchial cleft fistula to branchio-oto-renal syndrome: A case report and literature review

Branchial cleft abnormality is a common congenital neck malformation in children, which is caused by the abnormal development of the gill sac or gill groove. It is mainly manifested as a cyst in the sinus tract and fistula in the neck, as well as branchio-oto-renal syndrome (BORS). As a rare autosomal dominant genetic disease, the typical manifestations of BORS are hearing loss, abnormal branchial cleft development and renal dysplasia. In this paper, a patient was admitted to the hospital for bilateral branchial cleft fistulas combined with bilateral anterior auricular fistulas, auricular appendix, auricle dysplasia, external auditory canal stenosis, and hearing loss. The patient was diagnosed with BORS, and underwent fistulectomy of the neck and anterior ear, external auditory canal formation, and tympanoplasty. The aim of this report is to strengthen clinicians' understanding of BORS and reduce the rate of clinical missed diagnosis through our case report and literature review.

Targeted Exome Sequencing Provided Comprehensive Genetic Diagnosis of Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in children. The search for genetic causes of CAKUT has led to genetic diagnosis in approximately 5-20 % of CAKUT patients from Western countries. In this study, genetic causes of CAKUT in Korean children were sought using targeted exome sequencing (TES) of 60 genes reported to cause CAKUT in human or murine models. We identified genetic causes in 13.8% of the 94 recruited patients. Pathogenic single nucleotide variants of five known disease-causing genes, HNF1B, PAX2, EYA1, UPK3A, and FRAS1 were found in 7 cases. Pathogenic copy number variations of 6 patients were found in HNF1B, EYA1, and CHD1L. Genetic abnormality types did not significantly differ according to CAKUT phenotypes. Patients with pathogenic variants of targeted genes had syndromic features more frequently than those without (p < 0.001). This is the first genetic analysis study of Korean patients with CAKUT. Only one-seventh of patients were found to have pathogenic mutations in known CAKUT-related genes, indicating that there are more CAKUT-causing genes or environmental factors to discover.

DNA copy number variations in children with vesicoureteral reflux and urinary tract infections

Vesicoureteral reflux (VUR) is a complex, heritable disorder. Genome-wide linkage analyses of families affected by VUR have revealed multiple genomic loci linked to VUR. These loci normally harbor a number of genes whose biologically functional variant is yet to be identified. DNA copy number variations (CNVs) have not been extensively studied at high resolution in VUR patients. In this study, we performed array comparative genomic hybridization (aCGH) on a cohort of patients with a history of both VUR and urinary tract infection (UTI) with the objective of identifying genetic variations responsible for VUR and/or UTI susceptibility. UTI/VUR-associated CNVs were identified by aCGH results from the 192 Randomized Intervention for Children With Vesicoureteral Reflux (RIVUR) patients compared to 683 controls. Rare, large CNVs that are likely pathogenic and lead to VUR development were identified using stringent analysis criteria. Because UTI is a common affliction with multiple risk factors, we utilized standard analysis to identify potential disease-modifying CNVs that can contribute to UTI risk. Gene ontology analysis identified that CNVs in innate immunity and development genes were enriched in RIVUR patients. CNVs affecting innate immune genes may contribute to UTI susceptibility in VUR patients and may provide the first step in assisting clinical medicine in determining adverse outcome risk in children with VUR.

A de novo and novel mutation in the EYA1 gene in a Chinese child with branchio-oto-renal syndrome

Branchio-oto-renal (BOR) syndrome is a rare autosomal dominant disorder characterized by branchial cleft fistulae or cysts, preauricular pits, ear malformations, hearing loss, and renal anomalies. Mutations in the human homologue of the Drosophila eyes absent gene (EYA1) are the most common cause of BOR syndrome. PCR and direct sequencing were used to investigate all of the exons and exon-intron boundaries in the EYA1 gene in a patient with BOR syndrome from China. The patient was a child who displayed clinical features of BOR syndrome. Analysis of mutations in the EYA1 gene revealed a novel single base-pair deletion resulting in a truncated protein (c.1381delA; p.R461fs467X), and an analysis of mutations in the family revealed that this mutation was a de novo mutation. This is the first case of BOR syndrome in mainland China to be diagnosed based on clinical manifestations and mutations in the EYA1 gene. The novel c.1381delA mutation detected here expands the spectrum of known mutations in the EYA1 gene.

Identification of Isthmin 1 as a Novel Clefting and Craniofacial Patterning Gene in Humans

Orofacial clefts are one of the most common birth defects, affecting 1-2 per 1000 births, and have a complex etiology. High-resolution array-based comparative genomic hybridization has increased the ability to detect copy number variants (CNVs) that can be causative for complex diseases such as cleft lip and/or palate. Utilizing this technique on 97 nonsyndromic cleft lip and palate cases and 43 cases with cleft palate only, we identified a heterozygous deletion of Isthmin 1 in one affected case, as well as a deletion in a second case that removes putative 3' regulatory information. Isthmin 1 is a strong candidate for clefting, as it is expressed in orofacial structures derived from the first branchial arch and is also in the same "synexpression group" as fibroblast growth factor 8 and sprouty RTK signaling antagonist 1a and 2, all of which have been associated with clefting. CNVs affecting Isthmin 1 are exceedingly rare in control populations, and Isthmin 1 scores as a likely haploinsufficiency locus. Confirming its role in craniofacial development, knockdown or clustered randomly interspaced short palindromic repeats/Cas9-generated mutation of isthmin 1 in Xenopus laevis resulted in mild to severe craniofacial dysmorphologies, with several individuals presenting with median clefts. Moreover, knockdown of isthmin 1 produced decreased expression of LIM homeobox 8, itself a gene associated with clefting, in regions of the face that pattern the maxilla. Our study demonstrates a successful pipeline from CNV identification of a candidate gene to functional validation in a vertebrate model system, and reveals Isthmin 1 as both a new human clefting locus as well as a key craniofacial patterning gene.

A Gene Implicated in Activation of Retinoic Acid Receptor Targets Is a Novel Renal Agenesis Gene in Humans

Renal agenesis (RA) is one of the more extreme examples of congenital anomalies of the kidney and urinary tract (CAKUT). Bilateral renal agenesis is almost invariably fatal at birth, and unilateral renal agenesis can lead to future health issues including end-stage renal disease. Genetic investigations have identified several gene variants that cause RA, including EYA1, LHX1, and WT1 However, whereas compound null mutations of genes encoding α and γ retinoic acid receptors (RARs) cause RA in mice, to date there have been no reports of variants in RAR genes causing RA in humans. In this study, we carried out whole exome sequence analysis of two families showing inheritance of an RA phenotype, and in both identified a single candidate gene, GREB1L Analysis of a zebrafish greb1l loss-of-function mutant revealed defects in the pronephric kidney just prior to death, and F0 CRISPR/Cas9 mutagenesis of Greb1l in the mouse revealed kidney agenesis phenotypes, implicating Greb1l in this disorder. GREB1L resides in a chromatin complex with RAR members, and our data implicate GREB1L as a coactivator for RARs. This study is the first to associate a component of the RAR pathway with renal agenesis in humans.

Developmental Genetics and Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract (CAKUT) are common birth defects and the leading cause of end-stage renal disease in children. There is a wide spectrum of renal abnormalities, from mild hydronephrosis to more severe cases, such as bilateral renal dysplasia. The etiology of the majority of cases of CAKUT remains unknown, but there is increasing evidence that genomic imbalance contributes to the pathogenesis of CAKUT. Advances in human and mouse genetics have contributed to increased understanding of the pathophysiology of CAKUT. Mutations in genes involved in both transcription factors and signal transduction pathways involved in renal development are associated with CAKUT. Large cohort studies suggest that copy number variants, genomic, or de novo mutations may explain up to one-third of all cases of CAKUT. One of the major challenges to the use of genetic information in the clinical setting remains the lack of strict genotype-phenotype correlation. However, identifying genetic causes of CAKUT may lead to improved diagnosis of extrarenal complications. With the advent of decreasing costs for whole genome and exome sequencing, future studies focused on genotype-phenotype correlations, gene modifiers, and animal models of gene mutations will be needed to translate genetic advances into improved clinical care.

Actualizing the Benefits of Genomic Discovery in Pediatric Nephrology

The discovery of genetic variation associated with pediatric kidney disease has shed light on the biology underlying these conditions and, in some cases, has improved our clinical management of patients. We are challenged to continue the momentum of the genomic era in pediatric nephrology by identifying novel disease-associated genetic variation and translating these discoveries into clinical applications. This article reviews the diverse forms of genetic architecture that have been found to be associated with kidney diseases and traits. These include rare, fully penetrant variants responsible for Mendelian forms of disease, copy number variants, and more common variants associated with increased risk of disease. These discoveries have provided us with a greater understanding of the molecular mechanisms underlying these conditions and highlighted key pathways for potential intervention. In a number of areas, the identification of rare, fully penetrant variants is immediately clinically relevant, whether in regard to diagnostic testing, prediction of outcomes, or choice of therapies and interventions. This article discusses limitations in the deterministic view of rare, putatively causal mutations, a challenge increasing in importance as sequencing expands to many more genes and patients. This article also focusses on common genetic variants, using those found to be associated with focal segmental glomerulosclerosis in African-Americans, IgA nephropathy, chronic kidney disease (CKD), and estimated glomerular filtration rate (eGFR) as examples. Identifying common genetic variants associated with disease will complement other areas of genomic inquiry, lead to a greater biological understanding of disease, and will benefit pediatric nephrology patients.

Genome-wide mutational spectra analysis reveals significant cancer-specific heterogeneity

Cancer is widely recognized as a genetic disease in which somatic mutations are sequentially accumulated to drive tumor progression. Although genomic landscape studies are informative for individual cancer types, a comprehensive comparative study of tumorigenic mutations across cancer types based on integrative data sources is still a pressing need. We systematically analyzed ~10(6) non-synonymous mutations extracted from COSMIC, involving ~8000 genome-wide screened samples across 23 major human cancers at both the amino acid and gene levels. Our analysis identified cancer-specific heterogeneity that traditional nucleotide variation analysis alone usually overlooked. Particularly, the amino acid arginine (R) turns out to be the most favorable target of amino acid alteration in most cancer types studied (P < 10(-9), binomial test), reflecting its important role in cellular physiology. The tumor suppressor gene TP53 is mutated exclusively with the HYDIN, KRAS, and PTEN genes in large intestine, lung, and endometrial cancers respectively, indicating that TP53 takes part in different signaling pathways in different cancers. While some of our analyses corroborated previous observations, others indicated relevant candidates with high priority for further experimental validation. Our findings have many ramifications in understanding the etiology of cancer and the underlying molecular mechanisms in particular cancers.

Germinal mosaicism in a family with BO syndrome

OBJECTIVES

To clarify the existence of germinal mosaicism, we performed a genetic analysis of 2 siblings identified with an EYA1 mutation associated with branchiooto (BO) syndrome but who were born from normal parents.

METHODS

Detailed data from the 2 affected siblings were collected for clinical diagnosis, with haplotype analysis also performed to prove germinal mosaicism.

RESULTS

The 2 sisters showed characteristic clinical features of BO syndrome (middle and inner ear anomalies, microtia, and auditory canal stenosis/atresia). Haplotype analysis confirmed the genetic relationship between the affected sisters and their parents. The younger sister with auditory canal atresia received a bone-anchored hearing aid (Baha), a transcutaneous bone conduction hearing device, resulting in a good hearing outcome.

CONCLUSIONS

Based on the results of haplotype analysis, we proved that the BO syndrome in these cases was caused by germinal mosaicism of the EYA1 gene in either the mother or father. We also demonstrated that the bone-conduction hearing implant is a good option for BO patients with complex outer, middle, and inner ear anomalies.

Recurrent 8q13.2-13.3 microdeletions associated with branchio-oto-renal syndrome are mediated by human endogenous retroviral (HERV) sequence blocks

Background

Human endogenous retroviral (HERV) sequences are the remnants of ancient retroviral infection and comprise approximately 8% of the human genome. The high abundance and interspersed nature of homologous HERV sequences make them ideal substrates for genomic rearrangements. A role for HERV sequences in mediating human disease-associated rearrangement has been reported but is likely currently underappreciated.

Methods and Results

In the present study, two independent de novo 8q13.2-13.3 microdeletion events were identified in patients with clinical features of Branchio-Oto-Renal (BOR) syndrome. Nucleotide-level mapping demonstrated the identical breakpoints, suggesting a recurrent microdeletion including multiple genes such as EYA1, SULF1, and SLCO5A1, which is mediated by HERV1 homologous sequences.

Conclusions

These findings raise the potential that HERV sequences may more commonly underlie recombination of dosage sensitive regions associated with recurrent syndromes.

Branchio-oto-renal syndrome: comprehensive review based on nationwide surveillance in Japan

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder characterized by branchiogenic malformation, hearing loss and renal anomalies. The prevalence of BOR syndrome is 1/40,000 in Western countries, and nationwide surveillance in 2009-2010 identified approximately 250 BOR patients in Japan. Three causative genes for BOR syndrome have been reported thus far: EYA1, SIX1, and SIX5, but the causative genes for approximately half of all BOR patients remain unknown. This review article discusses the epidemiology, clinical symptoms, genetic background and management of BOR syndrome.