Muscular dystrophies and myopathies: the spectrum of mutated genes in the Czech Republic.

Inherited neuromuscular disorder (NMD) is a wide term covering different genetic disorders affecting muscles, nerves, and neuromuscular junctions. Genetic and clinical heterogeneity is the main drawback in a routine gene-by-gene diagnostics. We present Czech NMD patients with a genetic cause identified using targeted next-generation sequencing (NGS) and the spectrum of these causes. Overall 167 unrelated patients presenting NMD falling into categories of muscular dystrophies, congenital muscular dystrophies, congenital myopathies, distal myopathies, and other myopathies were tested by targeted NGS of 42 known NMD-related genes. Pathogenic or probably pathogenic sequence changes were identified in 79 patients (47.3%). In total, 37 novel and 51 known disease-causing variants were detected in 23 genes. In addition, variants of uncertain significance were suspected in 7 cases (4.2%), and in 81 cases (48.5%) sequence changes associated with NMD were not found. Our results strongly indicate that for molecular diagnostics of heterogeneous disorders such as NMDs, targeted panel testing has a high-clinical yield and should therefore be the preferred first-tier approach. Further, we show that in the genetic diagnostic practice of NMDs, it is necessary to take into account different types of inheritance including the occurrence of an autosomal recessive disorder in two generations of one family.

High frequency of SH3TC2 mutations in Czech HMSN I patients.

Charcot-Marie-Tooth (CMT) neuropathy type 4C (CMT4C) is an autosomal recessive (AR), demyelinating neuropathy with early spine deformities caused by mutations in the SH3TC2 gene. To determine the spectrum of SH3TC2 mutations in the Czech population, the entire coding region of SH3TC2 was sequenced in 60 unrelated Czech patients. The prevalent mutation was shown to be the p.Arg954Stop. Therefore, 412 additional patients referred for CMT testing were tested for the presence of p.Arg954Stop only. Of 60 patients in whom the SH3TC2 gene was sequenced, at least one mutation was detected in 13 (21.7%) patients and biallelic pathogenic mutations were detected in 7 (11.6%) patients. Of the 412 patients tested for p.Arg954Stop, the mutation was found in 8 patients (1.94%), 6 were homozygous and 2 were heterozygous. The second causative mutation was detected by sequencing in one of the patients but not in the other. Nine novel sequence variants were detected. Their pathogenicity was further tested in silico and in control samples. Mutations in the SH3TC2 gene are a frequent cause of demyelinating hereditary neuropathy among Czech patients. In total, at least one mutation was found in 21 unrelated patients. CMT4C seems to be the most frequent type of AR CMT and one of the most frequent of all CMT types. Mutation p.Arg954Stop is highly prevalent in the Czech population. Patients with demyelinating neuropathy along with non-dominant mode of inheritance and negative for CMT1A/hereditary neuropathy with liability to pressure palsy should be tested for the presence of the p.Arg954Stop mutation or other mutations in the SH3TC2 gene.

A 71-nucleotide deletion in the periaxin gene in a Romani patient with early-onset slowly progressive demyelinating CMT.

BACKGROUND: Mutations in the periaxin (PRX) gene cause autosomal recessive demyelinating neuropathy Charcot-Marie-Tooth (CMT) type 4F. To date, 10 non-sense or frameshift PRX mutations have been reported in patients with early-onset neuropathy and further disease course consistent with either Dejerine-Sottas neuropathy or slow-progressive demyelinating CMT. METHODS: We sequenced 59 patients from 55 Czech families including four unrelated patients of Romani (Gypsy) origin with early-onset CMT displaying decreased nerve conduction velocities. RESULTS: We identified a novel homozygous mutation c.3286_3356del71 (K1095fsX18) in one Romani patient showing very slow disease progression. Amongst non-Romani Czech CMT patients, PRX mutations have been proven to be very rare.

[Autosomal recessive ethnic diseases of Czech Gypsies]. / Autozomálne recesivní etnické choroby ceských Romu.

Roma (Gypsy ethnic) form a genetically isolated ethnical group of the identical origin with the world population of 10 to 14 millions derived from a limited number of so-called founders. Majority (about 8 millions) of Roma ethnic live in Europe, namely at Balkan and in the southwest of Europe. Roma have specific hereditary diseases, namely those caused by recessive genetic mutations. The molecular-genetic mechanism has been recently elucidated and confirmed in several diseases of the Roma population. Owing to the significant proportion of Roma in the population, patients with those diseases are possible to meet also in the Czech Republic. However, the diagnostics of those diseases is frequently difficult and they are often under diagnosed or misdiagnosed. The article gives examples of autosomal recessive diseases, which can be confirmed at the DNA level which occur in Roma population of the Czech Republic: syndrome of congenital cataract, facial dysmorphism and demyelinating neuropathy, non-syndromic prelingual deafness with GJB2 gene impairment and the congenital myastenic syndrome.