POLD1 variants leading to reduced polymerase activity can cause hearing loss without syndromic features.

DNA polymerase δ, whose catalytic subunit is encoded by POLD1, is responsible for synthesizing the lagging strand of DNA. Single heterozygous POLD1 mutations in domains with polymerase and exonuclease activities have been reported to cause syndromic deafness as a part of multisystem metabolic disorder or predisposition to cancer. However, the phenotypes of diverse combinations of POLD1 genotypes have not been elucidated in humans. We found that five members of a multiplex family segregating autosomal recessive nonsyndromic sensorineural hearing loss (NS-SNHL) have revealed novel compound heterozygous POLD1 variants (p.Gly1100Arg and a presumptive null function variant, p.Ser197Hisfs*54). The recombinant p.Gly1100Arg polymerase δ showed a reduced polymerase activity by 30-40%, but exhibited normal exonuclease activity. The polymerase activity in cell extracts from the affected subject carrying the two POLD1 mutant alleles was about 33% of normal controls. We suggest that significantly decreased polymerase δ activity, but not a complete absence, with normal exonuclease activity could lead to NS-SNHL.

Differential disruption of autoinhibition and defect in assembly of cytoskeleton during cell division decide the fate of human DIAPH1-related cytoskeletopathy.

BACKGROUND: Diaphanous-related formin 1 (DIA1), which assembles the unbranched actin microfilament and microtubule cytoskeleton, is encoded by DIAPH1. Constitutive activation by the disruption of autoinhibitory interactions between the N-terminal diaphanous inhibitory domain (DID) and C-terminal diaphanous autoregulatory domain (DAD) dysregulates DIA1, resulting in both hearing loss and blood cell abnormalities. METHODS AND RESULTS: Here, we report the first constitutively active mutant in the DID (p.A265S) of humans with only hearing loss and not blood cell abnormality through whole exome sequencing. The previously reported DAD mutants and our DID mutant (p.A265S) shared the finding of diminished autoinhibitory interaction, abnormally upregulated actin polymerisation activity and increased localisations at the plasma membrane. However, the obvious defect in the DIA1-driven assembly of cytoskeleton 'during cell division' was only from the DAD mutants, not from p.A265S, which did not show any blood cell abnormality. We also evaluated the five DID mutants in the hydrophobic pocket since four of these five additional mutants were predicted to critically disrupt interaction between the DID and DAD. These additional pathogenic DID mutants revealed varying degrees of defect in the DIA1-driven cytoskeleton assembly, including nearly normal phenotype during cell division as well as obvious impaired autoinhibition, again coinciding with our key observation in DIA1 mutant (p.A265S) in the DID. CONCLUSION: Here, we report the first mutant in the DID of humans with only hearing loss. The differential cell biological phenotypes of DIA1 during cell division appear to be potential determinants of the clinical severity of DIAPH1-related cytoskeletopathy in humans.

BGN Mutations in X-Linked Spondyloepimetaphyseal Dysplasia.

Spondyloepimetaphyseal dysplasias (SEMDs) comprise a heterogeneous group of autosomal-dominant and autosomal-recessive disorders. An apparent X-linked recessive (XLR) form of SEMD in a single Italian family was previously reported. We have been able to restudy this family together with a second family from Korea by segregating a severe SEMD in an X-linked pattern. Exome sequencing showed missense mutations in BGN c.439A>G (p.Lys147Glu) in the Korean family and c.776G>T (p.Gly259Val) in the Italian family; the c.439A>G (p.Lys147Glu) mutation was also identified in a further simplex SEMD case from India. Biglycan is an extracellular matrix proteoglycan that can bind transforming growth factor beta (TGF-ß) and thus regulate its free concentration. In 3-dimensional simulation, both altered residues localized to the concave arc of leucine-rich repeat domains of biglycan that interact with TGF-ß. The observation of recurrent BGN mutations in XLR SEMD individuals from different ethnic backgrounds allows us to define "XLR SEMD, BGN type" as a nosologic entity.

Type 1 Sialidosis Patient With a Novel Deletion Mutation in the NEU1 Gene: Case Report and Literature Review.

Recent advances in next-generation sequencing technologies have uncovered the genetic backgrounds of various diseases. Type 1 sialidosis (OMIM#256550) is a rare autosomal recessive lysosomal storage disease caused by a mutation in the NEU1 (OMIM * 608272) gene. In this study, we aimed to review the previous reports of type 1 sialidosis and compare those with the first case of type 1 sialidosis in Korea. A 36-year-old woman presented with progressive ataxia, myoclonus, and seizure since the age of 12. Whole-exome sequencing revealed a pathogenic missense variant c.928G > A (p.D310N) and novel c.15_16del (p.P6Qfs*21) of the NEU1 gene as final causal candidate as compound heterozygotes. We reviewed the literature and selected the clinical reports of genetically confirmed type 1 sialidosis patients. A total of 45 patients in 17 reports were identified. Cherry-red spot, myoclonus, ataxia, and seizure were reported in 51.2%, 100.0%, 87.8%, and 73.7% of patients, respectively. Abnormalities of cognitive function, EEG, and brain MRI and visual symptoms were reported in 22.2%, 40.7%, 66.7%, and 70.2% of patients, respectively. Overall, our patient showed similar clinical features to previous type 1 sialidosis patients, but she did not complain of visual symptoms despite having cherry-red spots. We summarize the clinical features of type 1 sialidosis and report the first case of type 1 sialidosis with novel deletion variant in the NEU1 gene in the Korean population. Our study suggests the importance of ophthalmologic examinations in patients with myoclonus, ataxia, and seizure who do not complain of visual symptoms.

Evaluation of somatic copy number estimation tools for whole-exome sequencing data.

Whole-exome sequencing (WES) has become a standard method for detecting genetic variants in human diseases. Although the primary use of WES data has been the identification of single nucleotide variations and indels, these data also offer a possibility of detecting copy number variations (CNVs) at high resolution. However, WES data have uneven read coverage along the genome owing to the target capture step, and the development of a robust WES-based CNV tool is challenging. Here, we evaluate six WES somatic CNV detection tools: ADTEx, CONTRA, Control-FREEC, EXCAVATOR, ExomeCNV and Varscan2. Using WES data from 50 kidney chromophobe, 50 bladder urothelial carcinoma, and 50 stomach adenocarcinoma patients from The Cancer Genome Atlas, we compared the CNV calls from the six tools with a reference CNV set that was identified by both single nucleotide polymorphism array 6.0 and whole-genome sequencing data. We found that these algorithms gave highly variable results: visual inspection reveals significant differences between the WES-based segmentation profiles and the reference profile, as well as among the WES-based profiles. Using a 50% overlap criterion, 13-77% of WES CNV calls were covered by CNVs from the reference set, up to 21% of the copy gains were called as losses or vice versa, and dramatic differences in CNV sizes and CNV numbers were observed. Overall, ADTEx and EXCAVATOR had the best performance with relatively high precision and sensitivity. We suggest that the current algorithms for somatic CNV detection from WES data are limited in their performance and that more robust algorithms are needed.

Mutational and phenotypic spectrum of OTOF-related auditory neuropathy in Koreans: eliciting reciprocal interaction between bench and clinics.

BACKGROUND: While auditory neuropathy spectrum disorder (ANSD) is a heterogeneous disorder and its management quite varies depending upon the etiology, even including self-resolution, OTOF is an important molecular etiology of prelingual ANSD and has emerged as an attractive target for implementation of precision medicine in terms of timing and prognosis prediction of auditory rehabilitation. However, to date, the literature is lacking in the genotype-phenotype relationship of this gene as well as efficient molecular testing strategy in the clinic in many populations and to make things more complicated in Koreans, the most prevalent variant p.Arg1939Gln among Korean ANSD children frequently evaded detection by next generation sequencing (NGS), resulting in delayed genetic diagnosis and late cochlear implantation (CI). The aims of this study are to document the mutational and phenotypic spectrum of OTOF-related ANSD (DFNB9) in the Korean population, further establishing genotype-phenotype correlation and proposing a set of the most commonly found OTOF variants to be screened first. METHODS: Genetic diagnosis through the NGS-based sequencing was made on patients with ANSD in two tertiary hospitals. Genotype and phenotypes of eleven DFNB9 patients were reviewed. For data analysis, Mann-Whitney test and Fisher's exact test were applied. RESULTS: This study disclosed four prevalent variants in Koreans: p.Arg1939Gln with an allele frequency of 40.9%, p.Glu841Lys (13.6%), p.Leu1011Pro and p.Arg1856Trp (9.1%). Three novel variants (c.4227 + 5G > C, p.Gly1845Glu, and p.Pro1931Thr) were identified. Interestingly, a significant association of p.Arg1939Gln with worse ASSR thresholds was observed despite consistently no ABR response. Ten of 11 DFNB9 patients received CI for auditory rehabilitation, showing favorable outcomes with more rapid improvement on early-CI group (age at CI ≤ 18 mo.) than late-CI group. CONCLUSIONS: This study included the largest Korean DFNB9 cohort to date and proposed a set of the most frequent four OTOF variants, allowing the potential prioritization of exons during Sanger sequencing. Further, a significant association of p.Arg1939Gln homozygotes with poor residual hearing was observed. We may have to suspect p.Arg1939Gln homozygosity in cases of poor auditory thresholds in ANSD children with putative negative OTOF variants solely screened by NGS. Reciprocal feedback between bench and clinics regarding DFNB9 would complement each other.

Clinical Application of Targeted Deep Sequencing in Solid-Cancer Patients and Utility for Biomarker-Selected Clinical Trials.

Molecular profiling of actionable mutations in refractory cancer patients has the potential to enable "precision medicine," wherein individualized therapies are guided based on genomic profiling. The molecular-screening program was intended to route participants to different candidate drugs in trials based on clinical-sequencing reports. In this screening program, we used a custom target-enrichment panel consisting of cancer-related genes to interrogate single-nucleotide variants, insertions and deletions, copy number variants, and a subset of gene fusions. From August 2014 through April 2015, 654 patients consented to participate in the program at Samsung Medical Center. Of these patients, 588 passed the quality control process for the 381-gene cancer-panel test, and 418 patients were included in the final analysis as being eligible for any anticancer treatment (127 gastric cancer, 122 colorectal cancer, 62 pancreatic/biliary tract cancer, 67 sarcoma/other cancer, and 40 genitourinary cancer patients). Of the 418 patients, 55 (12%) harbored a biomarker that guided them to a biomarker-selected clinical trial, and 184 (44%) patients harbored at least one genomic alteration that was potentially targetable. This study demonstrated that the panel-based sequencing program resulted in an increased rate of trial enrollment of metastatic cancer patients into biomarker-selected clinical trials. Given the expanding list of biomarker-selected trials, the guidance percentage to matched trials is anticipated to increase. IMPLICATIONS FOR PRACTICE: This study demonstrated that the panel-based sequencing program resulted in an increased rate of trial enrollment of metastatic cancer patients into biomarker-selected clinical trials. Given the expanding list of biomarker-selected trials, the guidance percentage to matched trials is anticipated to increase.

The Analysis of A Frequent TMPRSS3 Allele Containing P.V116M and P.V291L in A Cis Configuration among Deaf Koreans.

We performed targeted re-sequencing to identify the genetic etiology of early-onset postlingual deafness and encountered a frequent TMPRSS3 allele harboring two variants in a cis configuration. We aimed to evaluate the pathogenicity of the allele. Among 88 cochlear implantees with autosomal recessive non-syndromic hearing loss, subjects with GJB2 and SLC26A4 mutations were excluded. Thirty-one probands manifesting early-onset postlingual deafness were sorted. Through targeted re-sequencing, we detected two families with a TMPRSS3 mutant allele containing p.V116M and p.V291L in a cis configuration, p.[p.V116M; p.V291L]. A minor allele frequency was calculated and proteolytic activity was measured. A p.[p.V116M; p.V291L] allele demonstrated a significantly higher frequency compared to normal controls and merited attention due to its high frequency (4.84%, 3/62). The first family showed a novel deleterious splice site variant-c.783-1G>A-in a trans allele, while the other showed homozygosity. The progression to deafness was noted within the first decade, suggesting DFNB10. The proteolytic activity was significantly reduced, confirming the severe pathogenicity. This frequent mutant allele significantly contributes to early-onset postlingual deafness in Koreans. For clinical implication and proper auditory rehabilitation, it is important to pay attention to this allele with a severe pathogenic potential.

Deciphering intratumor heterogeneity using cancer genome analysis.

Intratumor heterogeneity within individual cancer tissues underlies the numerous phenotypes of cancer. Tumor subclones ultimately affect therapeutic outcomes due to their distinct molecular features. Drug-resistant subclones are present at a low frequency in tissues at the time of biopsy, but can also arise as a result of acquired somatic mutations. A number of different approaches have been utilized to understand the nature of intratumor heterogeneity. Clonal analysis using whole exome or genome sequencing data can help monitor subclones in the context of tumor progression. Multiregional biopsies permit the molecular characterization of subclones within tumors. Deep sequencing has also provided researchers with the ability to measure the low allele fraction variant within a small number of cells. Ultimately, single-cell sequencing will enable the identification of every minor population within a tumor microenvironment. In the clinical context, the ability to identify and monitor the subclonal architecture of a tumor is valuable for the development of precise cancer therapeutic methods.

Functional characterization of a novel loss-of-function mutation of PRPS1 related to early-onset progressive nonsyndromic hearing loss in Koreans (DFNX1): Potential implications on future therapeutic intervention.

BACKGROUND: The symptoms of phosphoribosyl pyrophosphate synthetase 1 (PRPS1) deficiency diseases have been reported to be alleviated by medication. In the present study, we report biochemical data that favor PRPS1 deficiency-related hearing loss as a potential target for pharmaceutical treatment. METHODS: We recruited 42 probands from subjects aged less than 15 years with a moderate degree of nonsyndromic autosomal-recessive or sporadic sensorineural hearing loss (SNHL) in at least one side. Molecular genetic testing, including targeted exome sequencing (TES) of 129 genes for deafness, and in silico prediction were performed. RESULTS: A strong candidate variant (p.A82P) of PRPS1 is co-segregated with SNHL in X-linked recessive inheritance from one Korean multiplex SNHL family. Subsequent measurement of in vitro enzymatic activities of PRPS1 from erythrocytes of affected and unaffected family members, as well as unrelated normal controls, confirmed a pathogenic role of this variant. In detail, compared to normal hearing controls (0.23-0.26 nmol/ml/h), the proband, the affected sibling and their normal hearing mother demonstrated a significantly decreased PRPS1 enzymatic activity (0.07, 0.03 and 0.11 nmol/ml/h, respectively). This novel loss-of-function mutation of PRPS1 (p.A82P) is the ninth and sixth most reported mutation in the world and in Asia, respectively. CONCLUSIONS: DFNX1 was found to account for approximately 2.4% (1/42) of moderate SNHL in a Korean pediatric population. Confirmation of PRPS1 activity deficiency and an audiologic phenotype that initially begins in a milder form of SNHL, as in our family, should indicate the need for rigorous genetic screening as early as possible.

Comprehensive genetic exploration of skeletal dysplasia using targeted exome sequencing.

PURPOSE: The purpose of this study was to evaluate the clinical utility of targeted exome sequencing (TES) as a molecular diagnostic tool for patients with skeletal dysplasia. METHODS: A total of 185 patients either diagnosed with or suspected to have skeletal dysplasia were recruited over a period of 3 years. TES was performed for 255 genes associated with the pathogenesis of skeletal dysplasia, and candidate variants were selected using a bioinformatics analysis. All candidate variants were confirmed by Sanger sequencing, correlation with the phenotype, and a cosegregation study in the family. RESULTS: TES detected "confirmed" or "highly likely" pathogenic sequence variants in 74% (71 of 96) of cases in the assured clinical diagnosis category and 20.3% (13 of 64 cases) of cases in the uncertain clinical diagnosis category. TES successfully detected pathogenic variants in all 25 cases of previously known genotypes. The data also suggested a copy-number variation that led to a molecular diagnosis. CONCLUSION: This study demonstrates the feasibility of TES for the molecular diagnosis of skeletal dysplasia. However, further confirmation is needed for a final molecular diagnosis, including Sanger sequencing of candidate variants with suspected, poorly captured exons.Genet Med 18 6, 563-569.

Hepatorenal fibrocystic diseases in children.

BACKGROUND: Hepatorenal fibrocystic diseases (HRFCDs) are a group of monogenic disorders characterized by developmental abnormalities involving the liver and kidney. In this study, we performed genotype and phenotype analyses of children with HRFCDs to determine the distribution of underlying diseases. METHODS: A total of 36 children with HRFCDs were recruited, with genetic tests being performed in 22 patients and 14 patients diagnosed clinically as having autosomal recessive polycystic kidney disease (ARPKD). RESULTS: In children with HRFCDs, ARPKD was the most common disease, found in 16/36 (44.4 %), followed by nephronophthisis 13 (NPHP13) in 11/36 (30.6 %) and Meckel-Gruber syndrome type 3 (MKS3) in 4/36 (11.1 %). Renal function deteriorated faster in children with NPHP13. The main hepatic pathology was Caroli disease in the NPHP13 patients, while most other patients had Caroli syndrome or congenital hepatic fibrosis. Of note, three of four MKS3 patients had an accompanying choledochal cyst. No ARPKD patient had other organ involvement, while several NPHP13 patients had ocular and/or neurodevelopmental involvement. In contrast, all MKS3 patients had severe ocular and neurodevelopmental involvement. CONCLUSIONS: NPHP13 is a major disease in the HRFCD category, and thorough evaluation of its clinical features, including kidney, liver and other organ involvement, may aid in the differential diagnosis of HRFCD.

The diagnostic application of targeted re-sequencing in Korean patients with retinitis pigmentosa.

BACKGROUND: Identification of the causative genes of retinitis pigmentosa (RP) is important for the clinical care of patients with RP. However, a comprehensive genetic study has not been performed in Korean RP patients. Moreover, the genetic heterogeneity found in sensorineural genetic disorders makes identification of pathogenic mutations challenging. Therefore, high throughput genetic testing using massively parallel sequencing is needed. RESULTS: Sixty-two Korean patients with nonsyndromic RP (46 patients from 18 families and 16 simplex cases) who consented to molecular genetic testing were recruited in this study and targeted exome sequencing was applied on 53 RP-related genes. Causal variants were characterised by selecting exonic and splicing variants, selecting variants with low allele frequency (below 1 %), and discarding the remaining variants with quality below 20. The variants were additionally confirmed by an inheritance pattern and cosegregation test of the families, and the rest of the variants were prioritised using in-silico prediction tools. Finally, causal variants were detected from 10 of 18 familial cases (55.5 %) and 7 of 16 simplex cases (43.7 %) in total. Novel variants were detected in 13 of 20 (65 %) candidate variants. Compound heterozygous variants were found in four of 7 simplex cases. CONCLUSION: Panel-based targeted re-sequencing can be used as an effective molecular diagnostic tool for RP.

Strong founder effect of p.P240L in CDH23 in Koreans and its significant contribution to severe-to-profound nonsyndromic hearing loss in a Korean pediatric population.

BACKGROUND: Despite the prevalence of CDH23 mutations in East Asians, its large size hinders investigation. The pathologic mutation p.P240L in CDH23 is common in East Asians. However, whether this mutation represents a common founder or a mutational hot spot is unclear. The prevalence of CDH23 mutations with prelingual severe-to-profound sporadic or autosomal recessive sensorineural hearing loss (arSNHL) is unknown in Koreans. METHODS: From September 2010 to October 2014, children with severe-to-profound sporadic or arSNHL without phenotypic markers, and their families, were tested for mutations in connexins GJB2, GJB6 and GJB3. Sanger sequencing of CDH23 p.P240L was performed on connexin-negative samples without enlarged vestibular aqueducts (EVA), followed by targeted resequencing of 129 deafness genes, including CDH23, unless p.P240L homozygotes were detected in the first screening. Four p.P240L-allele-linked STR markers were genotyped in 40 normal-hearing control subjects, and the p.P240L carriers in the hearing-impaired cohort, to identify the haplotypes. RESULTS: Four (3.1 %) of 128 children carried two CDH23 mutant alleles, and SLC26A4 and GJB2 accounted for 18.0 and 17.2 %, respectively. All four children showed profound nonsyndromic SNHL with minimal residual hearing. Interestingly, all had at least one p.P240L mutant allele. Analysis of p.P240L-linked STR markers in these children and other postlingual hearing-impaired adults carrying p.P240L revealed that p.P240L was mainly carried on a single haplotype. CONCLUSIONS: p.P240L contributed significantly to Korean pediatric severe arSNHL with a strong founder effect, with implications for future phylogenetic studies. Screening for p.P240L as a first step in GJB2-negative arSNHL Koreans without EVA is recommended.

Whole-exome sequencing reveals diverse modes of inheritance in sporadic mild to moderate sensorineural hearing loss in a pediatric population.

PURPOSE: This study was designed to delineate genetic contributions, if any, to sporadic forms of mild to moderate sensorineural hearing loss (SNHL) not related to GJB2 mutations (DFNB1) in a pediatric population. METHODS: We recruited 11 non-DFNB1 simplex cases of mild to moderate SNHL in children. We applied whole-exome sequencing to all 11 probands. We used a filtering strategy assuming that de novo variants of known autosomal dominant (AD) deafness genes, biallelic mutations in autosomal recessive (AR) genes, monoallelic mutations in X chromosome genes for males, and digenic inheritance could be associated. Candidate variants first were prioritized with allele frequency in public databases and confirmed by a phase or a segregation test in each family. Additional information from the literature or public databases was used to identify strong candidate variants. RESULTS: Strong candidate variants were detected in 5 of 11 probands (45.4%). A diverse mode of inheritance implicated the sporadic occurrence of the phenotype. AR mutations in OTOGL and SERPINB6 and digenic inheritance involving two deafness genes, GPR98 and PDZ7, were detected. A de novo AD mutation also was detected in TECTA and MYH14. No syndromic feature was detected in individuals with GPR98/PDZ7 or MYH14 variants in our cohort at this moment. CONCLUSION: Mild to moderate pediatric SNHL, even if sporadic, features a strong genetic etiology and can manifest via diverse modes of inheritance. In addition, a multidisciplinary approach should be used for a correct diagnosis.

Rare cases of congenital arthrogryposis multiplex caused by novel recurrent CHRNG mutations.

Multiple pterygium syndrome (MPS) is an autosomal recessively inherited condition that becomes evident before birth, with pterygium at multiple joints and akinesia. There are two forms of this syndrome that are differentiated by clinical severity: the milder form, Escobar type (OMIM#265000), and the more severe form, lethal type (OMIM#253290). Mutations in CHRNG, which encode the acetylcholine receptor gamma subunit, cause most cases of MPS. Here, we present three patients from two unrelated families showing multiple joint contractures in both the upper and lower limbs. High-arched palates with malocclusion, short neck and micrognathia were observed in all patients. Peripheral blood karyotypes were normal. Whole-exome sequencing analysis of the patients' genomes led to the discovery of identical missense (p.Pro143Arg) and frameshift deletion variants (p.Pro251fs*45) on CHRNG. These were rare cases of congenital arthrogryposis multiplex related to novel recessive CHRNG variants in two Korean kindred without apparent relatedness.

Skeletal overgrowth syndrome caused by overexpression of C-type natriuretic peptide in a girl with balanced chromosomal translocation, t(1;2)(q41;q37.1).

Chromosomal translocation of 2q37.1 just distal to the NPPC gene coding for C-type natriuretic peptide (CNP) and subsequent overproduction of CNP have been reported to cause a skeletal overgrowth syndrome. Loeys-Dietz syndrome (LDS) is one of marfanoid overgrowth syndromes, of which subtype IV is caused by haploinsufficiency of transforming growth factor beta 2 (TGFB2). We report on a girl with clinical phenotypes of overgrowth syndrome, including long and slim body habitus, macrodactyly of the big toe, scoliosis, ankle valgus deformity, coxa valga, slipped capital femoral epiphysis, and aortic root dilatation. Karyotyping revealed a balanced chromosomal translocation between 1q41 and 2q37.1, and the breakpoints could be mapped by targeted resequencing analysis. On chromosome 2q37.1, the translocation took place 200,365 bp downstream of NPPC, and serum level of the amino terminal of CNP was elevated. The contralateral site of translocation on chromosome 1q41 disrupted TGFB2 gene, presumed to cause its haploinsufficiency. This case supports the concept that NPPC is overexpressed because of the loss of a specific negative regulatory control in the normal chromosomal location, and demonstrates the effectiveness of targeted resequencing in the mapping of breakpoints.

Nephronophthisis 13: implications of its association with Caroli disease and altered intracellular localization of WDR19 in the kidney.

BACKGROUND: Nephronophthisis 13 (NPHP 13) is associated with mutations in the WDR19 gene, which encodes for a protein in the intraflagellar transport complex. Herein, we describe six additional cases accompanied by Caroli syndrome or disease. METHODS: Targeted exome sequencing covering 96 ciliopathy-related genes was performed for 48 unrelated Korean patients with a clinical suspicion of NPHP. Mutations were confirmed by Sanger sequencing. We evaluated the expression of WDR19 in the biopsied kidney by immunohistochemistry in patients and controls. RESULTS: We detected three (3/48, 6.3 %) unrelated index cases with WDR19 mutations. One of the cases involved two siblings with the same mutation. Later, we detected an additional index case with a similar phenotype of kidney and liver involvement by Sanger sequencing of WDR19. The p.R1178Q mutation was common in all patients. All of the six affected patients from four families progressed to chronic kidney disease. Of note, all six patients had Caroli syndrome or disease. Immunohistochemistry for WDR19 showed localized expression along the luminal borders of the renal tubular epithelium in controls, whereas it showed diffuse cytoplasmic staining in the affected patients. CONCLUSIONS: Caroli disease is a major extra-renal phenotype associated with mutations in WDR19 in the Korean population. In this study, we visually validated the expression pattern of mutant WDR19 protein in the kidneys of NPHP 13 patients. More data are needed to identify the true frequency of p.R1178Q. Functional studies including transfection assay will provide solid grounds for the pathogenicity of each mutation.

Atypical hemolytic uremic syndrome: Korean pediatric series.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a rare disease with a genetic predisposition. Few studies have evaluated the disease in the Asian population. We studied a Korean pediatric cohort to delineate the clinical characteristics and genotypes. METHODS: A multicenter cohort of 51 Korean children with aHUS was screened for mutations using targeted exome sequencing covering 46 complement related genes. Anti-complement-factor-H autoantibody (anti-CFH) titers were measured. Multiplex ligation-dependent probe amplification assay was performed to detect deletions in the complement factor-H related protein genes (CFHR) in the patients as well as in 100 healthy Korean controls. We grouped the patients according to etiology and compared the clinical features using Mann-Whitney U-test and chi-squared test. RESULTS: Fifteen patients (group A, 29.7%) had anti-CFH, and mutations were detected in 11 (group B, 21.6%), including one with combined mutations. The remaining 25 (group C, 49.0%) were negative for both. The prevalence of anti-CFH was higher than the worldwide level. Group A had a higher onset age than group B, although the difference was not significant. Group B had the worst renal outcome. Gene frequencies of homozygous CFHR1 deletion were 73.3%, 2.7% and 1% in group A, group B + C and the control, respectively. CONCLUSIONS: The incidence of anti-CFH in the present Korean aHUS cohort was high. Clinical outcomes largely conformed to the previous reports. Although the sample size was limited, this cohort provides a reassessment of clinicogenetic features of aHUS in Korean children.

Correction: Park et al. Genetic Study in Korean Pediatric Patients with Steroid-Resistant Nephrotic Syndrome or Focal Segmental Glomerulosclerosis. J. Clin. Med. 2020, 9, 2013.

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