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Approximately 20 cases of genome-wide uniparental disomy or diploidy (GWUPD) as mosaicism have previously been reported. We present the case of an 11-year-old deaf girl with a paternal uniparental diploidy or isodisomy with a genome-wide loss of heterozygosity (LOH). The patient was originally tested for non-syndromic deafness, and the novel variant p.V234I in the ESRRB gene was found in a homozygous state. Our female proband is the seventh patient diagnosed with GWUPD at a later age and is probably the least affected of the seven, as she has not yet presented any malignancy. Most, if not all, reported patients with GWUPD whose clinical details have been published have developed malignancy, and some of those patient developed malignancy several times. Therefore, our patient has a high risk of malignancy and is carefully monitored by a specific outpatient pediatric oncology program. This observation seems to be novel and unique in a GWUPD patient. Our study is also unique as it not only provides very detailed documentation of the genomic situations of various tissues but also reports differences in the mosaic ratios between the blood and saliva, as well as a normal biparental allelic situation in the skin and biliary duct. Additionally, we were able to demonstrate that the mosaic ratio in the blood remained stable even after 3 years and has not changed over a longer period.

BackgroundDe novo mutations in PURA have recently been described to cause PURA syndrome, a neurodevelopmental disorder characterised by severe intellectual disability (ID), epilepsy, feeding difficulties and neonatal hypotonia.ObjectivesTo delineate the clinical spectrum of PURA syndrome and study genotype-phenotype correlations.MethodsDiagnostic or research-based exome or Sanger sequencing was performed in individuals with ID. We systematically collected clinical and mutation data on newly ascertained PURA syndrome individuals, evaluated data of previously reported individuals and performed a computational analysis of photographs. We classified mutations based on predicted effect using 3D in silico models of crystal structures of Drosophila-derived Pur-alpha homologues. Finally, we explored genotype-phenotype correlations by analysis of both recurrent mutations as well as mutation classes.ResultsWe report mutations in PURA (purine-rich element binding protein A) in 32 individuals, the largest cohort described so far. Evaluation of clinical data, including 22 previously published cases, revealed that all have moderate to severe ID and neonatal-onset symptoms, including hypotonia (96%), respiratory problems (57%), feeding difficulties (77%), exaggerated startle response (44%), hypersomnolence (66%) and hypothermia (35%). Epilepsy (54%) and gastrointestinal (69%), ophthalmological (51%) and endocrine problems (42%) were observed frequently. Computational analysis of facial photographs showed subtle facial dysmorphism. No strong genotype-phenotype correlation was identified by subgrouping mutations into functional classes.ConclusionWe delineate the clinical spectrum of PURA syndrome with the identification of 32 additional individuals. The identification of one individual through targeted Sanger sequencing points towards the clinical recognisability of the syndrome. Genotype-phenotype analysis showed no significant correlation between mutation classes and disease severity.

The association of GNB4 with Charcot–Marie–Tooth (CMT) has recently been described in a publication by Soong et al. (Soong, et al., 2013). Here we present a patient with CMT in whom whole exome sequencing identified the mutation p.Lys57Glu in the GNB4 gene (NM_021629.3:c.169A>G). The patient, now 41 years old, is a sporadic case in the family. At the age of 35 he presented with severe disability (CMT neuropathy score 29), profound muscle atrophies, pes cavus and scoliosis. Previously, the patient was tested for PMP22 duplications/deletions and later also with 64 CMT gene panel, with no causal variant found. Subsequently, whole exome sequencing was performed. The p.Lys57Glu in the GNB4 gene was identified as the most probable causal variant, the mutation is not present in the patient's parents, neither in his unaffected sister, therefore we assume that the mutation arose de novo . Taken together, these findings support the causal and pathogenic character of the variant. Our report provides important evidence that GNB4 should become an established CMT gene and our findings confirm the original publication by Soong et al. (2013).

Schinzel–Giedion syndrome (SGS) is a very rare genetic disorder characterized by distinctive facial features, severe developmental delay, seizures, and skeletal abnormalities. Whole exome sequencing, Sanger sequencing, and correlation with already published variants and cases allowed us to identify two different de novo mutations in the SETBP1 gene: NM_015559.2 (SETBP1): c.2601C > G (p.Ser867Arg) and c. 2608 G > A (p.Gly870Ser) in two Czech patients presenting with SGS features. Both mutations are within exon 4 of SETBP1, supporting the notion that exon 4 represents the mutation hotspot of the gene in patients with SGS.

We detected a somatic mutation in the HLA-B gene in a Czech hematooncological patient. We followed the development of this somatic mutation during the transition from severe aplastic anaemia through to myelodysplastic syndrome to acute myeloid leukaemia until haploidentical related transplantation. The somatic mutation differs from HLA-B*14:02 in exon 3 resulting in an exchange from cysteine to serine at position 101 of the mature protein. Homology modelling of mutated S101 in HLA-B*14 indicated possible conformational changes, which might also result in an aberrant expression. The assumption is that somatic mutation arose as a possible result of a selection mediated by a protective immune response against leukaemia.

Hereditarni motoricke neuropatie (HMN), někdy tež nazývane distalni spinalni svalove atrofie (dSMA), jsou charakterizovane selektivnim postiženim motoricke casti periferniho nervoveho systemu. Představuji asi 10 % vsech hereditarnich neuropatii. Typickým znakem jsou symetricke svalove atrofie, ktere postihuji distalni svaly koncetin a vykazuji tzv. na delce nervu zavislý (length dependent) vzorec poruchy. Představuji heterogenni skupinu motorických neuropatii s významnou variabilitou fenotypu a velkou genetickou heterogenitou s různými typy dědicnosti. Aktualně bylo popsano vice než 12 různých genů, jejichž mutace jsou kauzalni pro různe formy HMN. Jednotlive formy se lisi věkem nastupu přiznaků, primarnim postiženim buď hornich nebo dolnich koncetin a kombinaci s dalsimi přiznaky např. s pyramidovými jevy, minoritnimi senzitivnimi poruchami, neuromyotonii, parezou hlasivek. Diagnostika se vedle kliniky a elektrodiagnostiky opira o molekularně geneticke testy a nalezy kauzalnich mutaci. Diferencialni diagnostika je důležita proti CMT nemoci, nemocem periferniho motoneuronu, vcetně juvenilni familarni formy amyotroficke lateralni sklerozy nebo ziskane multifokalni motoricke neuropatie. Kauzalni terapie neni k dispozici a zakladem je rehabilitacni a lazeňska lecba, dale proteticke a zdravotni pomůcky. V připadě stanoveni kauzalni mutace je důležite geneticke poradenstvi a v některých připadech i zajistěni prenatalni ci preimplantacni diagnostiky.

We describe a patient with early onset severe axonal Charcot-Marie-Tooth disease (CMT2) with dominant inheritance, in whom Sanger sequencing failed to detect a mutation in the mitofusin 2 (MFN2) gene because of a single nucleotide polymorphism (rs2236057) under the PCR primer sequence. The severe early onset phenotype and the family history with severely affected mother (died after delivery) was very suggestive of CMT2A and this suspicion was finally confirmed by a MFN2 mutation. The mutation p.His361Tyr was later detected in the patient by massively parallel sequencing with a gene panel for hereditary neuropathies. According to this information, new primers for amplification and sequencing were designed which bind away from the polymorphic sites of the patient's DNA. Sanger sequencing with these new primers then confirmed the heterozygous mutation in the MFN2 gene in this patient. This case report shows that massively parallel sequencing may in some rare cases be more sensitive than Sanger sequencing and highlights the importance of accurate primer design which requires special attention.

Introduction Neurodegenerative diseases of childhood present with progressive decline in cognitive, social, and motor function and are frequently associated with seizures in different stages of the disease. Here we report a patient with severe progressive neurodegeneration with drug-resistant epilepsy of unknown etiology from the age of 2 years. Methods and Results Using whole exome sequencing, we found heterozygous missense de novo variant c.628G > A (p.Glu210Lys) in the UBTF gene. This variant was recently described as de novo in 11 patients with similar neurodegeneration characterized by developmental decline initially confined to motor development followed by language regression, appearance of an extrapyramidal movement disorder, and leading to severe intellectual disability. In 3 of the 11 patients described so far, seizures were also present. Conclusions Our report expands the complex phenotype of neurodegeneration associated with the c.628G > A variant in the UBTF gene and helps to clarify the relation between this one single recurrent pathogenic variant described in this gene to date and its phenotype. The UBTF gene should be considered a novel candidate gene in neurodegeneration with or without epilepsy.

International audience; Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control neuronal excitability and their dysfunction has been linked to epileptogenesis but few individuals with neurological disorders related to variants altering HCN channels have been reported so far. In 2014, we described five individuals with epileptic encephalopathy due to de novo HCN1 variants. To delineate HCN1-related disorders and investigate genotype-phenotype correlations further, we assembled a cohort of 33 unpublished patients with novel pathogenic or likely pathogenic variants: 19 probands carrying 14 different de novo mutations and four families with dominantly inherited variants segregating with epilepsy in 14 individuals, but not penetrant in six additional individuals. Sporadic patients had epilepsy with median onset at age 7 months and in 36% the first seizure occurred during a febrile illness. Overall, considering familial and sporadic patients, the predominant phenotypes were mild, including genetic generalized epilepsies and genetic epilepsy with febrile seizures plus (GEFS+) spectrum. About 20% manifested neonatal/infantile onset otherwise unclassified epileptic encephalopathy. The study also included eight patients with variants of unknown significance: one adopted patient had two HCN1 variants, four probands had intellectual disability without seizures, and three individuals had missense variants inherited from an asymptomatic parent. Of the 18 novel pathogenic missense variants identified, 12 were associated with severe phenotypes and clustered within or close to transmembrane domains, while variants segregating with milder phenotypes were located outside transmembrane domains, in the intracellular N- and C-terminal parts of the channel. Five recurrent variants were associated with similar phenotypes. Using whole-cell patch-clamp, we showed that the impact of 12 selected variants ranged from complete loss-of-function to significant shifts in activation kinetics and/or voltage dependence. Functional analysis of three different substitutions altering Gly391 revealed that these variants had different consequences on channel biophysical properties. The Gly391Asp variant, associated with the most severe, neonatal phenotype, also had the most severe impact on channel function. Molecular dynamics simulation on channel structure showed that homotetramers were not conducting ions because the permeation path was blocked by cation(s) strongly complexed to the Asp residue, whereas heterotetramers showed an instantaneous current component possibly linked to deformation of the channel pore. In conclusion, our results considerably expand the clinical spectrum related to HCN1 variants to include common generalized epilepsy phenotypes and further illustrate how HCN1 has a pivotal function in brain development and control of neuronal excitability.

Background Recently, a study providing insight into GABRB3 mutational spectrum was published (Møller et al 2017). The authors report considerable pleiotropy even for single mutations and were not able to identify any genotype–phenotype correlations. Methods The proband (twin B) was referred for massively parallel sequencing of epilepsy-related gene panel because of hypotonia and neonatal seizures. The revealed variant was confirmed with Sanger sequencing in the proband and the twin A, and both parents were tested for the presence of the variant. Results We report a case of epilepsy of infancy with migrating focal seizures (EIMFS) of neonatal onset in monozygotic twins with a de novo novel GABRB3 variant p.Thr281Ala. The variant has a uniform presentation on an identical genomic background. In addition, early seizure-onset epilepsy associated with GABRB3 mutation has been until now described only for the p.Leu256Gln variant in the GABRB3 (Møller et al 2017, Myers et al 2016) located in the transmembrane domain just as the p.Thr281Ala variant described here. Conclusion De novo GABRB3 mutations may cause neonatal-onset EIMFS with early-onset hypotonia, respiratory distress, and severe developmental delay.

Hearing loss (HL) is the most common sensory deficit in humans. HL is an extremely heterogeneous condition presenting most frequently as a nonsyndromic (NS) condition inherited in an autosomal recessive (AR) pattern, termed DFNB. Mutations affecting the STRC gene cause DFNB type 16. Various types of mutations within the STRC gene have been reported from the U.S. and German populations, but no information about the relative contribution of STRC mutations to NSHL-AR among Czech patients is available.Two hundred and eighty-eight patients with prelingual NSHL, either sporadic (n = 207) or AR (n = 81), who had been previously tested negative for the mutations affecting the GJB2 gene, were included in the study. These patients were tested for STRC mutations by a quantitative comparative fluorescent polymerase chain reaction (QF-PCR) assay. In addition, 31 of the 81 NSHL-AR patients were analyzed by massively parallel sequencing using one of two different gene panels: 23 patients were analyzed by multiplex-ligation probe amplification (MLPA); and 9 patients by SNP microarrays.Causal mutations affecting the STRC gene (including copy number variations [CNVs] and point mutations) were found in 5.5% of all patients and 13.6% of the 81 patients in the subgroup with NSHL-AR.Our results provide strong evidence that STRC gene mutations are an important cause of NSHL-AR in Czech HL patients and are probably the second most common cause of DFNB. Large CNVs were more frequent than point mutations and it is reasonable to test them first by a QF-PCR method-a simple, accessible, and efficient tool for STRC CNV detection, which can be combined by MLPA.

Variants in the human X-linked cyclin-dependent kinase-like 5 (CDKL5) gene have been reported as being etiologically associated with early infantile epileptic encephalopathy type 2 (EIEE2). We report on two patients, a boy and a girl, with EIEE2 that present with early onset epilepsy, hypotonia, severe intellectual disability, and poor eye contact.Massively parallel sequencing (MPS) of a custom-designed gene panel for epilepsy and epileptic encephalopathy containing 112 epilepsy-related genes was performed. Sanger sequencing was used to confirm the novel variants. For confirmation of the functional consequence of an intronic CDKL5 variant in patient 2, an RNA study was done.DNA sequencing revealed de novo variants in CDKL5, a c.2578CT (p. Gln860*) present in a hemizygous state in a 3-year-old boy, and a potential splice site variant c.463+5GA in heterozygous state in a 5-year-old girl. Multiple in silico splicing algorithms predicted a highly reduced splice site score for c.463+5GA. A subsequent mRNA study confirmed an aberrant shorter transcript lacking exon 7.Our data confirmed that variants in the CDKL5 are associated with EIEE2. There is credible evidence that the novel identified variants are pathogenic and, therefore, are likely the cause of the disease in the presented patients. In one of the patients a stop codon variant is predicted to produce a truncated protein, and in the other patient an intronic variant results in aberrant splicing.

Hereditary motor and sensory neuropathy-type Lom (HMSNL), also known as CMT4D, a demyelinating neuropathy with late-onset deafness is an autosomal recessive disorder threatening Roma population worldwide. The clinical phenotype was reported in several case reports before the gene discovery. HMSNL is caused by a homozygous founder mutation p.Arg148* in the N-Myc downstream-regulated gene 1. Here, we report findings from the Czech Republic, where HMSNL was found in 12 Czech patients from eight families. In these 12 patients, 11 of the causes were due to p.Arg148* mutation inherited from both parents by the autosomal recessive mechanism. But in one case, the recessive mutation was inherited only from one parent (father) and unmasked owing to an uniparental isodisomy of the entire chromosome eight. The inherited peripheral neuropathy owing to an isodisomy of the whole chromosome pointed to an interesting, less frequent possibility of recessive disease and complications with genetic counseling.

Objectives To evaluate the contribution of eight small NSHL-AR (non-syndromic deafness, autosomal recessive) genes to hereditary hearing loss in Czech patients. Patients and Methods Unrelated Czech patients, adults and children, diagnosed with pre-lingual hereditary hearing loss with at least one similarly affected deaf sibling and with previously excluded mutations in the GJB2 gene were investigated by Sanger sequencing of the selected eight small NSHL-AR associated genes ( CABP2 - 51 patients, CIB2 - 45 patients, PJVK/DFNB59 - 53 patients, GJB3 - 46 patients, ILDR1 - 48 patients, LHFPL5 - 66 patients, LRTOMT - 60 patients, TMIE - 64 patients). Results Mutations were detected in the LHFPL5 (DFNB67) gene. The patient is heterozygote for two already described pathogenic variants (p.Tyr127Cys, p.Thr165Met). In five samples, five rare heterozygous variants (two novel) predicted as pathogenic were detected in genes CABP2, ILDR1, LHFPL5 and LRTOMT . Conclusion Mutations in eight small NSHL-AR genes are not a frequent cause of hereditary hearing loss in the Czech Republic. This diagnostic approach permitted the clarification of HL in only one patient – two heterozygous mutations were detected in LHFPL5 gene for the first time in Central Europe. As the use of panel base MPS certainly improves the diagnostic yield, future studies should rather profit from that diagnostic strategy.

We describe a patient with early onset severe axonal Charcot-Marie-Tooth disease (CMT2) with dominant inheritance, in whom Sanger sequencing failed to detect a mutation in the mitofusin 2 (MFN2) gene because of a single nucleotide polymorphism (rs2236057) under the PCR primer sequence. The severe early onset phenotype and the family history with severely affected mother (died after delivery) was very suggestive of CMT2A and this suspicion was finally confirmed by a MFN2 mutation. The mutation p.His361Tyr was later detected in the patient by massively parallel sequencing with a gene panel for hereditary neuropathies. According to this information, new primers for amplification and sequencing were designed which bind away from the polymorphic sites of the patient's DNA. Sanger sequencing with these new primers then confirmed the heterozygous mutation in the MFN2 gene in this patient. This case report shows that massively parallel sequencing may in some rare cases be more sensitive than Sanger sequencing and highlights the importance of accurate primer design which requires special attention.

Mutations in the HINT1 gene were recently discovered as being the major cause of autosomal recessive axonal neuropathy with neuromyotonia. This combination was clinically recognized and described previously in a few reports but is generally unknown. We aimed to establish the importance of HINT1 mutations as the cause of hereditary neuropathy and particularly hereditary motor neuropathy/axonal Charcot-Marie-Tooth (HMN/CMT2) among Czech patients. Overall, mutations in the HINT1 gene seem to be a surprisingly frequent cause of inherited neuropathy in our group of patients. Biallelic pathogenic mutations were found in 21 patients from 19 families. The prevalent mutation in the Czech population is the p.R37P (95 % of pathogenic alleles). Clinically, all patients with biallelic mutations presented with early onset of symptoms at the end of the first decade. Foot/toe extension weakness to plegia was present in almost all patients. Neuromyotonia was present in all but two patients. However, it had been properly recognized in only three patients prior to molecular genetic diagnosis. HINT1 mutations seem to be one of the most frequent causes of inherited neuropathy and are probably the most frequent cause of HMN in Czech patients. We suggest all HMN/CMT2 patients be tested for the presence of the prevalent mutation, the p.R37P.

Sir, The article by Auer-Grumbach et al. (2011) reporting that fibulin 5 ( FBLN5 ) mutations are also linked to inherited neuropathies helped us to clarify the cause of autosomal dominant, demyelinating hereditary motor and sensory neuropathy (HMSN I) in our long-time known, but unsolved, Czech family. Before this study was published, mutations in FBLN5 were associated only with the connective tissue disorder cutis laxa (Loeys et al. , 2002; Markova et al. , 2003; Lotery et al. , 2006; Nascimento et al. , 2010) and age-related macular degeneration leading to vision loss in those aged >50 years (Stone et al. , 2004; Lotery et al. , 2006). Auer-Grumbach et al. (2011) were the first to describe a large family with demyelinating Charcot–Marie–Tooth (CMT1) and linkage with the interval on chromosome 14. Subsequent resequencing of this region revealed only one novel variant c.1117 C > T (p.R373C) segregating with the disease in the family. Additional screening of 112 patients with Charcot–Marie–Tooth disease showed two other sequence variations in two patients with pure motor neuropathy and hyperelastic skin. The linkage with log of odds score >3.31 indicates the FBLN5 mutation as highly probably causal for HMSN I, but no functional study to confirm this was performed, and no other study on FBLN5 mutations in a family with HMSN has been published to date. This Austrian HMSN I family is the only one reported worldwide. We report a second family with non-syndromic inherited demyelinating motor and sensory neuropathy (HMSN I) with FBLN5 mutation and confirm FBLN5 mutations as the new cause of HMSN I. We used exome sequencing for clarification of the cause of HMSN I in a Czech family recruited in 2001 (Fig. 1A). The most frequent causes of CMT1 (CMT1 duplication/HNPP …