[AP4-assocated hereditary spastic paraplegias]. / AP4-svyazannye nasledstvennye spasticheskie paraplegii.

OBJECTIVE: In the course of studies of spastic paraplegias in Russian patients to detect AP4-associated forms, estimate their proportion in the total SPG group and analyze clinical and molecular characteristics. MATERIAL AND METHODS: Five families of Russian ethnicity: four with SPG47, one with SPG51 (4 girls and a boy aged 2.5-9 years) were studied. Clinical and genealogical methods, whole-exome sequencing (WES) and verification by familial Sanger sequencing were used. RESULTS: In our total group, including 118 families with 21 different forms, SPG AP4-associated forms accounted for 4.2% owing mainly to SPG47 (3.4%, 5th place in SPG structure; 20% and 2nd place in AE subgroup.) In non-consanguineous, unrelated SPG47 families three patients had identical genotypes: homozygosity for an earlier reported mutation c.1160_1161 delCA (p.Thr387ArgfsTer30) in AP4B1 exon 6; the 4th patient was compound-heterozygous for the same mutation and novel c.1240C>T (p.Gln414Ter) in exon 7. Frequency of c.1160_1161 delCA may be caused by founder effect in Slavic populations though the idea needs additional studies. The SPG51 patient was compound heterozygous for novel AP4E1 mutations c.2604delA (p.Ser868fs) and c.3346A>G (p.Arg1116Gly). Parent's heterozygosity in all cases was confirmed by Sanger sequencing. Phenotypes were typical: early development delay, muscle hypotony transforming into sever spasticity, mental deficiency, microceplaly (in all SPG47 cases), epilepsy (in 3 SPG47 and SPG51 cases), MRI changes, mainly hydrocephalus and/or hypoplasia of corpus callosum (in 3 SPG47 cases) and few extraneural signs. CONCLUSION: AP4-associated SPG should be taken into consideration in patients with early-onset severe nervous diseases mimicking non-genetic organic CNS disorders and massive exome sequencing (WES or other variants) should be performed.

Mitochondrial DNA maintenance disorders in 102 patients from different parts of Russia: Mutational spectrum and phenotypes.

Currently, pathogenic variants in more than 25 nuclear genes, involved in mtDNA maintenance, are associated with human disorders. mtDNA maintenance disorders manifest with a wide range of phenotypes, from severe infantile-onset forms of myocerebrohepatopathy to late-onset forms of myopathies, chronic progressive external ophthalmoplegia, and parkinsonism. This study represents the results of molecular genetic analysis and phenotypes of 102 probands with mtDNA maintenance disorders. So far, this is the largest Russian cohort for this group of diseases. Mutations were identified in 10 mtDNA maintenance genes: POLG (n = 59), DGUOK (n = 14), TWNK (n = 14), TK2 (n = 8), MPV17 (n = 2), OPA3 (n = 1), FBXL4 (n = 1), RRM2B (n = 1), SUCLG1 (n = 1) and TYMP (n = 1). We review a mutation spectrum for the DGUOK and TWNK genes, that can be specific for the Russian population. In 34 patients we measured the blood mtDNA copy number and showed its significant reduction. Novel variants were found in 41 cases, which significantly expands the mutational landscape of mtDNA maintenance disorders.

[Diversity of CACNA1A-related disorders]. / Raznoobrazie boleznei, svyazannykh s genom CACNA1A.

Four cases of autosomal dominant CNS disorders related to CACNA1A mutations and detected by massive parallel sequencing are reported: a non-familial case of episodic ataxia type 2 (EA2) with the previously reported mutation c.269_270insA (p.Tyr90Ter) in a 35-year-old man; familial hemiplegic migraine type 1 (FHM1) in a girl aged 3 years 10 months and her mother aged 38 yrs with a novel mutation 1829C>T (p.Ser610Phe), members of a family with 4 patients and incomplete penetrance; developmental and epileptic encephalopathy 42 (DEE42) in a 9-year-old girl and a 5-year-old boy from different families with the identical de novo mutation c.2137G>A (p.Ala713Thr) reported earlier. Clinical and genetic characteristics are analyzed compared to literature.

KIF1A-related autosomal dominant spastic paraplegias (SPG30) in Russian families.

BACKGROUND: Spastic paraplegia type 30 (SPG30) caused by KIF1A mutations was first reported in 2011 and was initially considered a very rare autosomal recessive (AR) form. In the last years, thanks to the development of massive parallel sequencing, SPG30 proved to be a rather common autosomal dominant (AD) form of familial or sporadic spastic paraplegia (SPG),, with a wide range of phenotypes: pure and complicated. The aim of our study is to detect AD SPG30 cases and to examine their molecular and clinical characteristics for the first time in the Russian population. METHODS: Clinical, genealogical and molecular methods were used. Molecular methods included massive parallel sequencing (MPS) of custom panel 'spastic paraplegias' with 62 target genes complemented by familial Sanger sequencing. One case was detected by the whole -exome sequencing. RESULTS: AD SPG30 was detected in 10 unrelated families, making it the 3rd (8.4%) most common SPG form in the cohort of 118 families. No AR SPG30 cases were detected. In total, 9 heterozygous KIF1A mutations were detected, with 4 novel and 5 known mutations. All the mutations were located within KIF1A motor domain. Six cases had pure phenotypes, of which 5 were familial, where 2 familial cases demonstrated incomplete penetrance, early onset and slow relatively benign SPG course. All 4 complicated cases were caused by novel mutations without familial history. The phenotypes varied from severe in two patients (e.g. lack of walking, pronounced mental retardation) to relatively mild non-disabling symptoms in two others. CONCLUSION: AD SPG30 is one of the most common forms of SPG in Russia, the disorder has pronounced clinical variability while pure familial cases represent a significant part.

[Clinical and genetic characteristics of epilepsy caused by mutations in the PCDH19 gene (OMIM: 300088)]. / Kliniko-geneticheskie kharakteristiki épilepsii, obuslovlennoi mutatsiiami v gene PCDH19 (OMIM: 300088).

AIM: To analyze clinical and genetic characteristics of PCDH19-associated epilepsy in a sample of patients from the Russian population. MATERIAL AND METHODS: The sample of patients with early epileptic encephalopathies included 16 people aged 10 month to 30 years. All patients underwent neurological examination according to standard methods, exome sequencing and EEG monitoring. RESULTS: Most of the identified mutations led to a shift in the reading frame or the formation of a termination codon. Six of them were duplications, four were deletions of one nucleotide, and three were nonsense mutations. Consistent with earlier studies, the authors identified the polymorphism of clinical manifestations of seizures that did not depend on the type of mutation and its localization. CONCLUSION: Based on the study of the clinical and genetic characteristics of the patients, the authors conclude that the so-called 'hot spots' are present in the PCDH19 gene, which are more common in the group of patients with mutations in this gene, and that the clinical picture of early infantile epileptic encephalopathy type 9 is variable.

HINT1 gene pathogenic variants: the most common cause of recessive hereditary motor and sensory neuropathies in Russian patients.

Pathogenic variants in the HINT1 gene lead to hereditary axonopathy with neuromyotonia. However, many studies show that neuromyotonia may remain undiagnosed, while axonopathy is the major clinical finding. The most common cause of neuromyotonia and axonopathy, especially in patients of Slavic origin, is a c.110G>C (p.Arg37Pro) pathogenic variant in homozygous or compound heterozygous state. In this study, we analyzed a peripheral neuropathy caused by pathogenic variants in the HINT1 gene and evaluated its contribution to the hereditary neuropathy structure. The studied group included 1596 non-related families diagnosed with hereditary motor and sensory neuropathy (HMSN). The results show that HINT1 gene pathogenic variants make a significant contribution to the hereditary neuropathy epidemiology in Russian patients. They account for at least 1.9% of all HMSN cases and 9% of axonopathy cases. The most common HINT1 pathogenic variant in Russian patients is the c.110G>C (p.Arg37Pro) substitution. Its allelic frequency is 0.2% (95% CI 0.19-0.21%), carrier frequency is 1 in 250 people in Russian Federation, and the estimated disease incidence is 1 in 234,000 individuals. It was determined that the cause of this pathogenic variant's prevalence is the founder effect.

[New allelic variants of non-syndromic mental retardation of type 20 caused by mutations in the MEF2C gene]. / Novye allel'nye varianty nesindromal'noi umstvennoi otstalosti 20-go tipa, obuslovlennoi mutatsiiami v gene.

AIM: To determine clinical and genetic characteristics of patients with non-syndromic mental retardation (NMR), type 20 with autosomal dominant type of inheritance (OMIM: 613443). MATERIAL AND METHODS: Fourteen patients were studied including four patients with mutations in the MEF2C gene revealed by exome sequencing. Three of the four mutations in the gene were found for the first time. RESULTS: Based on a comparative analysis of the clinical manifestations of 4 observed patients and 9 patients with type 20 NMR described in the literature, the authors determined common clinical characteristics of this syndrome. In most cases with delayed psycho-speech development and convulsive syndrome, the patients were expected to have various variants of early epileptic encephalopathies, in which presence of convulsive paroxysms leads to intellectual deficit, while in the case of NMR, the delay in development can be noted long before the onset of seizures. CONCLUSION: Exome sequencing is the most effective method of NMR diagnosis.

[Clinical and genetic characteristics of facioscapulohumeral muscular dystrophy Landuzi-Dezherina type 1]. / Kliniko-geneticheskie kharakteristiki litse-plechelopatochnoi miodistrofii Landuzi-Dezherina tipa 1.

AIM: To describe clinical and genetic characteristics of patients from the Russian population with a variety of phenotypic variants of facioscapulohumeral muscular dystrophy Landuzi-Dezherina type 1 (FSHD 1). MATERIAL AND METHODS: The material for the study were blood samples of 16 patients from 15 unrelated families residing in the territory of the Russian Federation, between the ages of 6 to 66 years, with symptoms of FSHD. Diagnosis was based on genealogical data analysis, neurological examination, electroneuromyographic study, indicators of activity of creatine phosphokinase (CPK) in the blood serum and molecular genetic analysis of the results, aimed at the analysis of macrosatellite D4Z4 repeats on chromosome 4. RESULTS AND CONCLUSION: The study established the diagnosis of FSHD1 in 75% of patients. The correlation of the severity and phenotypic spectrum of FSHD1 with the age of onset was found. There was the significant clinical heterogeneity even among the 1st degree relatives in the same family. The correlation between macrosatellite D4Z4 repeats and clinical features of FSHD1 described previously in the literature was not observed.

[Genetics and treatment of early infantile epileptic encephalopathies]. / Genetika i differentsirovannoe lechenie rannikh epilepticheskikh entsefalopatii.

Epileptic encephalopathies (EE) are the group of progressive conditions with various etiologies that can produce neurocognitive deficit both per se and due to constant epileptiform discharges. Epileptic encephalopathies constitute about 15% of epilepsy in childhood and 40% of all seizures occurring in the first 3 years of life. Ten syndrome forms of EE are identified. Genetic factors contribute to 70-80% of all epileptic diseases and approximately 40% of idiopathic epilepsies have a monogenic mode of inheritance. Thirty-five genes of EE have been identified and the search is still continuing. The marked genetic heterogeneity of early EE, including 16 with autosomal-dominant-, 13 with autosomal-recessive-, 4 with X-linked recessive- and 2 with X-linked autosomal inheritance, was shown. The article describes differentiated approaches to the treatment of certain EE syndromes. Recent publications record the effectiveness of targeted therapy for certain forms of monogenic early EE (stiripentol in SCN1A mutations, diphenine in SCN8A mutations, levetiracetam in STXBP1 mutations). These results indicate the necessity for accurate diagnosis of genetic variants in early infantile EE for preventive actions in burdened families and for increasing the effectiveness of treatment.

[Clinical/genetic characteristics of patients with congenital muscular dystrophy caused by mutations in the LMNA gene].

OBJECTIVE: To study clinical/genetic characteristics of congenital muscular dystrophy caused by mutations in the LMNA gene in 5 patients from the Russian population. MATERIAL AND METHODS: DNA samples of 42 probands, aged from 2 months to 9 years, with characteristic signs of congenital muscular dystrophy from nonrelated families were studied. The diagnosis was based on the results of genealogical analysis, neurological examination, serum creatine phosphokinase activity, results of electroneuromyography. RESULTS AND CONCLUSION: In the Russian population, the frequency of congenital muscular dystrophy caused by mutations in the LMNA gene is not less than 12% of all cases of this group of diseases. The results indicate the presence of major mutation c.94_96delAAC in the LMNA gene. Specific phenotypic features of this form of congenital muscular dystrophy with symptoms of progressive flaccid paralysis with predominant lesions of axial muscles and plantar flexor muscles of the foot are described.

[The spectrum of CLCN1 gene mutations in patients with nondystrophic Thomsen's and Becker's myotonias].

Thomsen's and Becker's diseases are the most prevalent nondystrophic myotonias. Their frequency varies, according to different sources, from 1 : 100 000 to 1 : 10 000. Thomsen's myotonia is autosomal dominant, and Becker's myotonia is autosomal recessive. Both diseases result from mutations of the CLCN1 gene encoding chloride ion channels of skeletal muscles. Molecular genetic analysis of the CLCN1 gene has been performed in patients with diagnoses of nondystrophic Thomsen's and Becker's myotonias living in the Russian Federation. A sample of 79 unrelated probands with nondystrophic Thomsen's and Becker's myotonias and 44 their relatives has been formed in the Laboratory of DNA Diagnosis of the Medical Genetic Research Center of the Russian Academy of Medical Sciences. Forty CLCN1 gene mutations have been found in a total of 118 chromosomes of 66 probands, including 21 familial and 45 sporadic cases. About half the mutations detected (45%) have been found for the first time; they are not described in the SNP database (ncbi.nlm.nih.gov). The following mutations (substitutions) have been detected in more than one chromosome, accounting for a total of 59.3% of chromosomes with mutations: Glyl90Ser (5.9%), c.1437-1450del14 (9.3%), Ala493Glu (5.1%), Thr550Met (3.4%), Tyr686Stop (5.1%), and Arg894Stop (30.5%).

[Heterozygous carrier rate for type I-IV proximal spinal muscular atrophy in Chuvashes, Udmurts, and residents of the Moscow region].

The first estimation of the heterozygous carrier rates for the SMN1 gene deletions and SMN2 gene duplications in populations of Russia has been performed. The numbers of SMNgene copies have been determined in samples from Chuvash and Udmurt populations, as well the population of the Moscow region, by means of multiplex ligation-dependent probe amplification. The heterozygous carrier rates for the CMA gene were 2.7% (1 : 37 people), 2.8% (1 : 36 people), and 2.8% (1 : 36 people) in Chuvashes, Udmurts, and residents of the Moscow region, respectively. The SMN2 duplication frequencies have been determined in the studied groups. It is 1.5, 4, and 2.5% in Chuvashes, Udmurts, and residents of the Moscow region, respectively. The high SMN2 duplication frequency in Udmurts may explain why the SMN1 heterozygous carriage frequency in this population was overestimated in earlier PCR-RFLP analyses.

[Clinical-genetic characteristics of hereditary motor-sensory neuropathy type 1 X].

Data of own researches and the review of the literary data for studying pathogenesis and features of HMSN, type 1 Х caused by mutations in gene GJB1 are presented in this paper. X-linked HMSN is the genetic variant second for frequency in Russian, it constitute 22% from total of patients of this group. Features of this genetic variant are considerable distinction in weight clinical displays at patients man's and female. It is shown that at the majority of female patients clinical displays are expressed less, and at 20% were absent at all. The assumption is come out that at indicators of CNV from 35 to 52 m/s, it is necessary to conduct research in gene GJB1 especially at patients of a female and as to carry out search of mutations at all relatives with HMSN, type 1 X even in the absence of complaints from their party.

[Clinical-genetic analysis of limb-girdle muscular dystrophy 2 type I].

Seventy four patients with clinical presentation of LGMD and probably autosomal-recessive type of inheritance were examined. Five different mutations of FKRP gene responsible for LGMD2 type I were detected in eight (10.8%) patients. Two of them с.341C>G, c.826C>A were described before and three c.229C>T, с.265C>T, с.1078G>C were found for the first time. The significant clinical polymorphism due to the difference in age of manifestation and severity of clinical presentation was identified.

[Clinical-genetic correlations in the hereditary motor-sensor neuropathy caused by mutations in the MPZ (P0) gene].

Hereditary motor-sensor neuropathy (HMSN) caused by mutations in the MPZ (P0) gene is a rare variant of hereditary demyelinating polyneuropathies that makes up 5-10% of all cases in different populations. Based on the complex examination of patients of the Russian Federation with different MPZ (P0) mutations, we obtained clinical-genetic, electromyographic and molecular-genetic characteristics of HMSN caused by mutations in the MPZ (P0) gene. Peculiarities of clinical presentations in patients with HMSN, types 1B and 2I, are presented. Diagnostic criteria of these genetic variants have been formed. The new allelic variants of HMSN caused by mutations in the MPZ (P0) gene are described. The distribution of mutations by protein domains has been analyzed.

[Clinical-genetic characteristics of limb girdle-muscular dystrophy type 2A].

We present the results of the molecular genetic study of 26 patients, aged from 12 to 60 years, from 24 unrelated families with limb girdle-muscular dystrophy (LGMD) type 2A. The disease duration varied from 6 months to 30 years. The diagnosis of LGMD 2capital A, Cyrillic was confirmed by molecular genetic methods basing on the presence of a CAPN3 mutation in homozygous, compound-heterozygous and heterozygous state. The Leyden-Moebius variant that is characterized by the primary affection of muscles of pelvic girdle and shin with the gradual progression of the pathological process in shoulder girdle muscles was the most frequent in the Russian population. Tip-toe walking or difficulties in walking upstairs and running were the first symptoms reported by patients. In contrast to criteria of the European Neuromuscular Center, the characteristic symptoms of the disease were early contractures of ankle joints and pseudohypertrophy of gastrocnemius muscles. The major c.550delA mutation in the CAPN3 gene was identified in 70% of Russian patients.

[Syndrome Leigh caused by mutations in the SURF1 gene: clinical and molecular-genetic characteristics].

Syndrome Leigh (SL) or subacute necrotizing encephalomyelopathy - is a rare hereditary genetically heterogeneous disease from the group of mitochondrial encephalomyopathies. Twenty-seven children with SL were examined using clinical, laboratory (measuring lactate levels), MRI and molecular-genetic (polymerase chain reaction genotyping of 9 exons of the SURF1 gene) studies. The mean age of manifestation was 11,6 months. The main manifestations of SL were: delay of psychomotor development, diffuse muscle hypertonic, cerebellar syndrome, ophthalmoparesis, hypertrichosis. The disease had a progressive course with the loss of acquired skills. The blood lactate concentration was increased on average up to 3,1 mM/ml (from 1,9 to 5,1 mM/ml) compared to normal values (1,8 mM/ml). Brain MRI revealed the subcortical and cortical atrophy (80% of cases), symmetrical distinctly delineated hyperintense lesions on T2-weighted images (demyelization) in the basal ganglia and the brain stem (50%), as well as in the cerebellum (25%). Genotyping identified 7 different mutations. The most frequent (64,8%) was the deletion of 2 nucleotides (845delCT) in exon 8 that was in line with early data of Polish researchers thus indicating the Slavic origin of this mutation. Other mutations (574-575insCTGT, 311-321del10insAT and IVS8-1G>) were also frequent in the Russian population.

[Hereditary motor and sensory neuropathy type 4A].

The first in the Russian Federation clinical cases of patients with autosomal-recessive type of hereditary motor and sensory neuropathy, type 4A, (HMSN 4A) are presented. In all cases, the diagnosis has been verified using molecular-genetic methods (DNA diagnostics). An analysis of features of clinical manifestations was performed in patients, aged from 5 to 34 years, with different disease duration (from 3-to 29 years). Criteria of selection of patients for DNA diagnostics for searching mutations in the GDAP1 gene are specified.

[Genetic epidemiological study of Bashkortostan Republic: the effect of genetic structure of population on the load of monogenic hereditary diseases].

Here we present the data obtained during medical genetic examination of the population of five districts of Bashkortostan Republic (Burzyanskii, Baimakskii, Abzelilovskii, Salavatskii, and Arkhangelskii) populated with 168050 persons including 135748 Bashkirs. The study involved all the population of the districts including each ethnic group and was conducted according to standard protocol developed in the Laboratory of Genetic Epidemiology, Medical Genetic Research Center, Russian Academy of Medical Sciences. Based on segregation analysis, the values of prevalence rates of the major types of Mendelian pathology (AD, AR, and X- linked diseases) was calculated in five regions of the Republic as well as for Bashkirs alone. Significant differences in the prevalence rates of AD and AR pathologies between individual districts, in particular upon division in rural and urban population, was observed. The prevalence rates comparison of monogenic hereditary pathology among Bashkirs compared to other previously examined populations have shown that the patterns of the hereditary disease load in the inspected districts of Bashkortostan were similar to that observed in the population of some districts in Udmurtia, Marii El and Chuvashiya. Russian European populations have shown significantly lower load of hereditary diseases. Correlation analysis of local inbreeding, endogamy and prevalence rates of AD and AR pathologies has shown that development of hereditary diseases load is significantly affected by gene drift.