Derivation of iPS cell line (ICGi032-A) from a patient affected with fragile X syndrome.

Trinucleotide repeat expansion diseases such as fragile X syndrome are of great interest to study since the mechanism of its development is still unknown. IPS cell lines are some of the most convenient models for studying. The ICGi032-A iPS cell line was obtained from the peripheral blood mononuclear cells of the patient affected with fragile X syndrome. ICGi032-A iPS cell line have a normal karyotype, expression of pluripotency markers and can differentiate in vitro into the cells of three germ layers.

Establishment of an induced pluripotent stem cell line (ICGi026-A) from peripheral blood mononuclear cells of a patient with fragile X syndrome.

Expansion over 200 CGG repeats in FMR1 gene causes inherited intellectual disability or autism spectrum disorder named as fragile X syndrome. Despite the known cause fragile X syndrome pathogenesis has not been specified yet. The ICGi026-A iPSCs line was obtained by the reprogramming of the peripheral blood mononuclear cells from a 9-year-old boy with fragile X syndrome. The ICGi026-A iPSCs expressed pluripotency markers, had a normal male karyotype (46, XY) and had the capacity to in vivo differentiate into the cells of three germ layers.

[Method for the Molecular Cytogenetic Visualization of Fragile Site FRAXA].

Fragile X syndrome is one of the most common reasons for human hereditary mental retardation. It is associated with the expansion of CGG repeats in the 5'-untranslated region of the FMR1 gene, which results in the suppression of its expression and the development of the disease. At present, methods based on PCR and Southern blot analysis are used for diagnostics of the fragile X syndrome. The presence of a fragile site FRAXA on the X chromosome is typical for patients with this pathology. We developed a method of visualizing this site in cell cultures obtained from patients using the fluorescent in situ hybridization (FISH) and the combination of two probes. The method allows one to detect five types of signals on the X chromosome, three of which are normal, while two are associated with the emergence of fragile site FRAXA. An analysis of the distribution of all signal types in cell lines from healthy individuals and patients with fragile X syndrome demonstrated that the method allows one to determine differences between lines with a high statistical significance and that it is applicable to detecting cells that are carriers of the syndrome.

[Chromatin changes caused by CGG repeat expansion in fmr1 gene].

Fragile X syndrome is inheritable neurodegenerative disease with frequency 1/4000-1/6000. It is the main cause of inheritable mental retardation. Progression of the disorder is caused by CGG repeat expansion in 5' UTR of fmr1 (fragile X mental retardation 1) gene. Normal allele contains ≤ 54 repeats. Allele containing 55-200 repeats induce fragile X-associated disorders: fragile X-associated tremor/ataxia syndrome and fragile-X associated primary ovarian insufficiency. Allele containing ≥ 200 repeats induce fragile X syndrome. Absence of FMRP protein is the main reason for the syndrome progression. FMRP is RNA-binding protein responsible for neuronal differentiation. In case of increasing CGG triplets number the expression of fmr1 gene is repressed. Results of CGG expansion are DNA methylation, histone methylation and deacetylation. Repression transcription factors bind such chromatin and lead to disorder progression. In this review we discuss the mechanisms of heterochromatinization induced by CGG repeat expansion in the promoter region of fmr1 gene.