[Increased LAMP1 Expression Enhances SARS-CoV-1 and SARS-CoV-2 Production in Vero-Derived Transgenic Cell Lines].

Coronaviridae is a family of single-stranded RNA (ssRNA) viruses that can cause diseases with high mortality rates. SARS-CoV-1 and MERS-CoV appeared in 2002-2003 and 2012, respectively. A novel coronavirus, SARS-CoV-2, emerged in 2019 in Wuhan (China) and has caused more than 5 million deaths in worldwide. The entry of SARS-CoV-1 into the cell is due to the interaction of the viral spike (S) protein and the cell protein, angiotensin-converting enzyme 2 (ACE2). After infection, virus assembly occurs in Golgi apparatus-derived vesicles during exocytosis. One of the possible participants in this process is LAMP1 protein. We established transgenic Vero cell lines with increased expression of human LAMP1 gene and evaluated SARS-CoV-1 and SARS-CoV-2 production. An increase in the production of both viruses in LAMP1-expressing cells when compared with Vero cells was observed, especially in the presence of trypsin during infection. From these results it can be assumed that LAMP1 promotes SARS-CoV-1 and SARS-CoV-2 production due to enhanced exocytosis.

[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.

Comparative chromosome painting in Carnivora and Pholidota.

The order of Carnivora has been very well characterized with over 50 species analyzed by chromosome painting and with painting probe sets made for 9 Carnivora species. Representatives of almost all families have been studied with few exceptions (Otariidae, Odobenidae, Nandiniidae, Prionodontidae). The patterns of chromosome evolution in Carnivora are discussed here. Overall, many Carnivora species retained karyotypes that only slightly differ from the ancestral carnivore karyotype. However, there are at least 3 families in which the ancestral carnivore karyotype has been severely rearranged - Canidae, Ursidae and Mephitidae. Here we report chromosome painting of yet another Carnivora species with a highly rearranged karyotype, Genetta pardina. Recurrent rearrangements make it difficult to define the ancestral chromosomal arrangement in several instances. Only 2 species of pangolins (Pholidota), a sister order of Carnivora, have been studied by chromosome painting. Future use of whole-genome sequencing data is discussed in the context of solving the questions that are beyond resolution of conventional banding techniques and chromosome painting.

Increased LAMP1 Expression Enhances SARS-CoV-1 and SARS-CoV-2 Production in Vero-Derived Transgenic Cell Lines.

Coronaviridae is a family of single-stranded RNA (ssRNA) viruses that can cause diseases with high mortality rates. SARS-CoV-1 and MERS-CoV appeared in 2002‒2003 and 2012, respectively. A novel coronavirus, SARS-CoV-2, emerged in 2019 in Wuhan (China) and has caused more than 5 million deaths in worldwide. The entry of SARS-CoV-1 into the cell is due to the interaction of the viral spike (S) protein and the cell protein, angiotensin-converting enzyme 2 (ACE2). After infection, virus assembly occurs in Golgi apparatus-derived vesicles during exocytosis. One of the possible participants in this process is LAMP1 protein. We established transgenic Vero cell lines with increased expression of human LAMP1 gene and evaluated SARS-CoV-1 and SARS-CoV-2 production. An increase in the production of both viruses in LAMP1-expressing cells when compared with Vero cells was observed, especially in the presence of trypsin during infection. From these results it can be assumed that LAMP1 promotes SARS-CoV-1 and SARS-CoV-2 production due to enhanced exocytosis.

A transgenic cell line with inducible transcription for studying (CGG)n repeat expansion mechanisms.

There are more than 30 inherited human disorders connected with repeat expansion (myotonic dystrophy type I, Huntington's disease, Fragile X syndrome). Fragile X syndrome is the most common reason for inherited intellectual disability in the human population. The ways of the expansion development remain unclear. An important feature of expanded repeats is the ability to form stable alternative DNA secondary structures. There are hypotheses about the nature of repeat instability. It is proposed that these DNA secondary structures can block various stages of DNA metabolism processes, such as replication, repair and recombination and it is considered as the source of repeat instability. However, none of the hypotheses is fully confirmed or is the only valid one. Here, an experimental system for studying (CGG)n repeat expansion associated with transcription and TCR-NER is proposed. It is noteworthy that the aberrations of transcription are a poorly studied mechanism of (CGG)n instability. However, the proposed systems take into account the contribution of other processes of DNA metabolism and, therefore, the developed systems are universal and applicable for various studies. Transgenic cell lines carrying a repeat of normal or premutant length under the control of an inducible promoter were established and a method for repeat instability quantification was developed. One type of the cell lines contains an exogenous repeat integrated into the genome by the Sleeping Beauty transposon; in another cell line, the vector is maintained as an episome due to the SV40 origin of replication. These experimental systems can serve for finding the causes of instability and the development of therapeutic agents. In addition, a criterion was developed for the quantification of exogenous (CGG)n repeat instability in the transgenic cell lines' genome.

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.

Mapping of KIT adjacent sequences on canid autosomes and B chromosomes.

B chromosomes are often considered to be one of the most mysterious elements of karyotypes (Camacho, 2004). It is generally believed that mammalian B chromosomes do not contain any protein coding genes. The discovery of a conserved KIT gene in Canidae B chromosomes has changed this view. Here we performed analysis of sequences surrounding KIT in B chromosomes of the fox and raccoon dog. The presence of the RPL23A pseudogene was shown in canid B chromosomes. The 3' end fragment of the KDR gene was found in raccoon dog B chromosomes. The size of the B-specific fragment homologous to the autosome fragment was estimated to be a minimum of 480 kbp in both species. The origin and evolution of B chromosomes in Canidae are discussed.