Hereditary spastic paraplegia (HSP) comprises a heterogeneous group of neurodegenerative disorders, it share common symptom - of progressive lower spastic paraparesis. The most common autosomal dominant (AD) forms of HSP are SPG4 (SPAST gene) and SPG3 (ATL1 gene). In the current research we investigated for the first time the distribution of pathogenic mutations in SPAST and ATL1 genes within a large cohort of Russian HSP patients (122 probands; 69 famillial cases). We determined the frequencies of genetic abnormalities using Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and Next Generation Sequencing (NGS) of targeted gene panels. As a result, SPG4 was diagnosed in 30.3% (37/122) of HSP cases, where the familial cases represented 37.7% (26/69) of SPG4. In total 31 pathogenic and likely pathogenic variants were detected in SPAST, with 14 new mutations. Among all detected SPAST variants, 29% were gross deletions and duplications. The proportion of SPG3 variants in Russian cohort was 8.2% (10/122) that were all familial cases. All 10 detected ATL1 mutations were missense substitutions, most of which were in the mutational hot spots of 4, 7, 8, 12 exons, with 2 novel mutations. This work will be helpful for the populational genetics of HSP understanding.

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Mutations in LMNA gene produce a wide spectrum of disorders called laminopathies. In this article, the first cases of laminopathies from Russia are reported. In 10 unrelated families, 9 different mutations were identified: Asp47His, Gly232Arg, c.[781_783delAAG, 781insGTGGAGCAGTATAAGAAA], Arg249Gln (in two families), Arg377His, Arg541His, Ala350Pro, Leu52Pro, and Gly635Asp. Mutations Arg249Gln, Arg377His, and Arg541His were reported previously, others are novel. Four cases present de novo mutations, among them two cases with Arg249Gln are found. Because this mutation occurred de novo also in other reported cases, a mutational 'hot spot' was supposed. Three phenotypes were observed: autosomal dominant (AD) Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle MD type 1B, and AD dilated cardiomyopathy with conduction defect type 1A (DCM1A). Atypical clinical presentations were a very severe EDMD and an infantile DCM1A.

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Intellectual development disorder (IDD) is characterized by a general deficit in intellectual and adaptive functioning. In recent years, there has been a growing interest in studying the genetic structure of IDD. Of particular difficulty are patients with non-specific IDD, for whom it is impossible to establish a clinical diagnosis without complex genetic diagnostics. We examined 198 patients with non-specific IDD from 171 families using whole-exome sequencing and chromosome microarray analysis. Hereditary forms of IDD account for at least 35.7% of non-specific IDD, of which 26.9% are monogenic forms. Variants in the genes associated with the BAF (SWI/SNF) complex were the most frequently identified. We were unable to identify phenotypic features that would allow differential diagnosis of monogenic and microstructural chromosomal rearrangements in non-specific IDD at the stage of clinical examination, but due to its higher efficiency, exome sequencing should be the diagnostic method of the highest priority study after the standard examination of patients with NIDD in Russia.

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