Publications by authors named "Igor N Lebedev"

23 Publications

  • Page 1 of 1

Differential DNA Methylation of the IMMP2L Gene in Families with Maternally Inherited 7q31.1 Microdeletions is Associated with Intellectual Disability and Developmental Delay.

Cytogenet Genome Res 2021 Apr 13:1-15. Epub 2021 Apr 13.

Research Institute of Medical Genetics, Tomsk National Research Medical Center, Tomsk, Russian Federation.

Most copy number variations (CNVs) in the human genome display incomplete penetrance with unknown underlying mechanisms. One such mechanism may be epigenetic modification, particularly DNA methylation. The IMMP2L gene is located in a critical region for autism susceptibility on chromosome 7q (AUTS1). The level of DNA methylation was assessed by bisulfite sequencing of 87 CpG sites in the IMMP2L gene in 3 families with maternally inherited 7q31.1 microdeletions affecting the IMMP2L gene alone. Bisulfite sequencing revealed comparable levels of DNA methylation in the probands, healthy siblings without microdeletions, and their fathers. In contrast, a reduced DNA methylation index and increased IMMP2L expression were observed in lymphocytes from the healthy mothers compared with the probands. A number of genes were upregulated in the healthy mothers compared to controls and downregulated in probands compared to mothers. These genes were enriched in components of the ribosome and electron transport chain, as well as oxidative phosphorylation and various degenerative conditions. Differential expression in probands and mothers with IMMP2L deletions relative to controls may be due to compensatory processes in healthy mothers with IMMP2L deletions and disturbances of these processes in probands with intellectual disability. The results suggest a possible partial compensation for IMMP2L gene haploinsufficiency in healthy mothers with the 7q31.1 microdeletion by reducing the DNA methylation level. Differential DNA methylation of intragenic CpG sites may affect the phenotypic manifestation of CNVs and explain the incomplete penetrance of chromosomal microdeletions.
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http://dx.doi.org/10.1159/000514491DOI Listing
April 2021

A cookbook for DNase Hi-C.

Epigenetics Chromatin 2021 Mar 20;14(1):15. Epub 2021 Mar 20.

Institute of Cytology and Genetics SB RAS, Lavrentjeva ave 10, Novosibirsk, Russia.

Background: The Hi-C technique is widely employed to study the 3-dimensional chromatin architecture and to assemble genomes. The conventional in situ Hi-C protocol employs restriction enzymes to digest chromatin, which results in nonuniform genomic coverage. Using sequence-agnostic restriction enzymes, such as DNAse I, could help to overcome this limitation.

Results: In this study, we compare different DNAse Hi-C protocols and identify the critical steps that significantly affect the efficiency of the protocol. In particular, we show that the SDS quenching strategy strongly affects subsequent chromatin digestion. The presence of biotinylated oligonucleotide adapters may lead to ligase reaction by-products, which can be avoided by rational design of the adapter sequences. Moreover, the use of nucleotide-exchange enzymes for biotin fill-in enables simultaneous labelling and repair of DNA ends, similar to the conventional Hi-C protocol. These improvements simplify the protocol, making it less expensive and time-consuming.

Conclusions: We propose a new robust protocol for the preparation of DNAse Hi-C libraries from cultured human cells and blood samples supplemented with experimental controls and computational tools for the evaluation of library quality.
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http://dx.doi.org/10.1186/s13072-021-00389-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7981840PMC
March 2021

46,XY,r(8)/45,XY,-8 Mosaicism as a Possible Mechanism of the Imprinted Birk-Barel Syndrome: A Case Study.

Genes (Basel) 2020 Dec 9;11(12). Epub 2020 Dec 9.

Research Institute of Medical Genetics, Tomsk National Research Medical Center (NRMC), Ushaika Street 10, 634050 Tomsk, Russia.

Ring chromosome 8 (r(8)) is one of the least frequent ring chromosomes. Usually, maternal chromosome 8 forms a ring, which can be lost from cells due to mitotic instability. The 8q24 region contains the imprinted gene, which is expressed from the maternal allele. Heterozygous mutations are associated with the imprinting disorder Birk-Barel syndrome. Here, we report a 2.5-year-old boy with developmental delay, microcephaly, dysmorphic features, diffuse muscle hypotonia, feeding problems, motor alalia and noncoarse neurogenic type of disturbance of muscle electrogenesis, partially overlapping with Birk-Barel syndrome phenotype. Cytogenetic analysis of lymphocytes revealed his karyotype to be 46,XY,r(8)(p23q24.3)[27]/45,XY,-8[3]. A de novo 7.9 Mb terminal 8p23.3p23.1 deletion, a 27.1 Mb 8p23.1p11.22 duplication, and a 4.4 Mb intact segment with a normal copy number located between them, as well as a 154-kb maternal gene deletion (9p21.2) with unknown clinical significance were identified by aCGH + SNP array. These aberrations were confirmed by real-time PCR. According to FISH analysis, the 8p23.1-p11.22 duplication was inverted. The ring chromosome originated from maternal chromosome 8. Targeted massive parallel sequencing did not reveal the mutations associated with Birk-Barel syndrome. Our data allow to assume that autosomal monosomy with inactive allele of imprinted gene arising from the loss of a ring chromosome in some somatic cells may be an etiological mechanism of mosaic imprinting disorders, presumably with less severe phenotype.
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http://dx.doi.org/10.3390/genes11121473DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7763634PMC
December 2020

LINE-1 retrotransposon methylation in chorionic villi of first trimester miscarriages with aneuploidy.

J Assist Reprod Genet 2021 Jan 10;38(1):139-149. Epub 2020 Nov 10.

Research Institute of Medical Genetics, Tomsk National Research Medical Center, Nab. R. Ushaiki, 10, Tomsk, Russia.

Purpose: High frequency of aneuploidy in meiosis and cleavage stage coincides with waves of epigenetic genome reprogramming that may indicate a possible association between epigenetic mechanisms and aneuploidy occurrence. This study aimed to assess the methylation level of the long interspersed repeat element 1 (LINE-1) retrotransposon in chorionic villi of first trimester miscarriages with a normal karyotype and aneuploidy.

Methods: The methylation level was assessed at 19 LINE-1 promoter CpG sites in chorionic villi of 141 miscarriages with trisomy of chromosomes 2, 6, 8-10, 13-15, 16, 18, 20-22, and monosomy X using massive parallel sequencing.

Results: The LINE-1 methylation level was elevated statistically significant in chorionic villi of miscarriages with both trisomy (45.2 ± 4.3%) and monosomy X (46.9 ± 4.2%) compared with that in induced abortions (40.0 ± 2.4%) (p < 0.00001). The LINE-1 methylation levels were specific for miscarriages with different aneuploidies and significantly increased in miscarriages with trisomies 8, 14, and 18 and monosomy X (p < 0.05). The LINE-1 methylation level increased with gestational age both for group of miscarriages regardless of karyotype (R = 0.21, p = 0.012) and specifically for miscarriages with trisomy 16 (R = 0.48, p = 0.007). LINE-1 methylation decreased with maternal age in miscarriages with a normal karyotype (R = - 0.31, p = 0.029) and with trisomy 21 (R = - 0.64, p = 0.024) and increased with paternal age for miscarriages with trisomy 16 (R = 0.38, p = 0.048) and monosomy X (R = 0.73, p = 0.003).

Conclusion: Our results indicate that the pathogenic effects of aneuploidy in human embryogenesis can be supplemented with significant epigenetic changes in the repetitive sequences.
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http://dx.doi.org/10.1007/s10815-020-02003-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823001PMC
January 2021

Aneuploidy and DNA Methylation as Mirrored Features of Early Human Embryo Development.

Genes (Basel) 2020 09 17;11(9). Epub 2020 Sep 17.

Research Institute of Medical Genetics, Tomsk National Research Medical Center, 634050 Tomsk, Russia.

Genome stability is an integral feature of all living organisms. Aneuploidy is the most common cause of fetal death in humans. The timing of bursts in increased aneuploidy frequency coincides with the waves of global epigenetic reprogramming in mammals. During gametogenesis and early embryogenesis, parental genomes undergo two waves of DNA methylation reprogramming. Failure of these processes can critically affect genome stability, including chromosome segregation during cell division. Abnormal methylation due to errors in the reprogramming process can potentially lead to aneuploidy. On the other hand, the presence of an entire additional chromosome, or chromosome loss, can affect the global genome methylation level. The associations of these two phenomena are well studied in the context of carcinogenesis, but here, we consider the relationship of DNA methylation and aneuploidy in early human and mammalian ontogenesis. In this review, we link these two phenomena and highlight the critical ontogenesis periods and genome regions that play a significant role in human reproduction and in the formation of pathological phenotypes in newborns with chromosomal aneuploidy.
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http://dx.doi.org/10.3390/genes11091084DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7564410PMC
September 2020

Generation of GABAergic striatal neurons by a novel iPSC differentiation protocol enabling scalability and cryopreservation of progenitor cells.

Cytotechnology 2020 Oct 9;72(5):649-663. Epub 2020 Jun 9.

Federal Research Center Institute of Cytology and Genetics, The Siberian Branch of the Russian Academy of Sciences, 10 Lavrentiev Ave, Novosibirsk, Russian Federation, 630090.

Cell models are promising tools for studying hereditary human neurodegenerative diseases. Neuronal derivatives of pluripotent stem cells provide the opportunity to investigate different stages of the neurodegeneration process. Therefore, easy and large-scale production of relevant cell types is a crucial barrier to overcome. In this work, we present an alternative protocol for iPSC differentiation into GABAergic medium spiny neurons (MSNs). The first stage involved dual-SMAD signalling inhibition through treatment with SB431542 and LDN193189, which results in the generation of neuroectodermal cells. Moreover, we used bFGF as a neuronal survival factor and dorsomorphin to inhibit BMP signalling. The combined treatment of dorsomorphin and SB431542 significantly enhanced neuronal induction, which was confirmed by the increased expression of the telencephalic-specific markers SOX1 and OTX2 as well as the forebrain marker PAX6. The next stage involved the derivation of actively proliferating MSN progenitor cells. An important feature of our protocol at this stage is the ability to perform prolonged cultivation of precursor cells at a high density without losing phenotypic properties. Moreover, the protocol enables multiple expansion steps (> 180 days cultivation) and cryopreservation of MSN progenitors. Therefore, this method allows quick production of a large number of neurons that are relevant for basic research, large-scale drug screening, and toxicological studies.
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http://dx.doi.org/10.1007/s10616-020-00406-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547944PMC
October 2020

Delineation of Clinical Manifestations of the Inherited Xq24 Microdeletion Segregating with sXCI in Mothers: Two Novel Cases with Distinct Phenotypes Ranging from UBE2A Deficiency Syndrome to Recurrent Pregnancy Loss.

Cytogenet Genome Res 2020 30;160(5):245-254. Epub 2020 May 30.

Chromosomal microdeletion syndromes present with a wide spectrum of clinical phenotypes that depend on the size and gene content of the affected region. In a healthy carrier, epigenetic mechanisms may compensate for the same microdeletion, which may segregate through several generations without any clinical symptoms until the epigenetic modifications no longer function. We report 2 novel cases of Xq24 microdeletions inherited from mothers with extremely skewed X-chromosome inactivation (sXCI). The first case is a boy presenting with X-linked mental retardation, Nascimento type, due to a 168-kb Xq24 microdeletion involving 5 genes (CXorf56, UBE2A, NKRF, SEPT6, and MIR766) inherited from a healthy mother and grandmother with sXCI. In the second family, the presence of a 239-kb Xq24 microdeletion involving 3 additional genes (SLC25A43, SLC25A5-AS1, and SLC25A5) was detected in a woman with sXCI and a history of recurrent pregnancy loss with a maternal family history without reproductive wastages or products of conception. These cases provide evidence that women with an Xq24 microdeletion and sXCI may be at risk for having a child with intellectual disability or for experiencing a pregnancy loss due to the ontogenetic pleiotropy of a chromosomal microdeletion and its incomplete penetrance modified by sXCI.
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http://dx.doi.org/10.1159/000508050DOI Listing
September 2020

Opening up new horizons for psychiatric genetics in the Russian Federation: moving toward a national consortium.

Mol Psychiatry 2019 08 21;24(8):1099-1111. Epub 2019 Jan 21.

First Saint Petersburg Pavlov State Medical University, Saint Petersburg, Russian Federation.

We provide an overview of the recent achievements in psychiatric genetics research in the Russian Federation and present genotype-phenotype, population, epigenetic, cytogenetic, functional, ENIGMA, and pharmacogenetic studies, with an emphasis on genome-wide association studies. The genetic backgrounds of mental illnesses in the polyethnic and multicultural population of the Russian Federation are still understudied. Furthermore, genetic, genomic, and pharmacogenetic data from the Russian Federation are not adequately represented in the international scientific literature, are currently not available for meta-analyses and have never been compared with data from other populations. Most of these problems cannot be solved by individual centers working in isolation but warrant a truly collaborative effort that brings together all the major psychiatric genetic research centers in the Russian Federation in a national consortium. For this reason, we have established the Russian National Consortium for Psychiatric Genetics (RNCPG) with the aim to strengthen the power and rigor of psychiatric genetics research in the Russian Federation and enhance the international compatibility of this research.The consortium is set up as an open organization that will facilitate collaborations on complex biomedical research projects in human mental health in the Russian Federation and abroad. These projects will include genotyping, sequencing, transcriptome and epigenome analysis, metabolomics, and a wide array of other state-of-the-art analyses. Here, we discuss the challenges we face and the approaches we will take to unlock the huge potential that the Russian Federation holds for the worldwide psychiatric genetics community.
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http://dx.doi.org/10.1038/s41380-019-0354-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6756082PMC
August 2019

A Familial Small Supernumerary Marker Chromosome 15 Associated with Cryptic Mosaicism with Two Different Additional Marker Chromosomes Derived de novo from Chromosome 9: Detailed Case Study and Implications for Recurrent Pregnancy Loss.

Cytogenet Genome Res 2018 23;156(4):179-184. Epub 2018 Nov 23.

We report a case of familial small supernumerary marker chromosome 15 in a phenotypically normal female with 4 recurrent spontaneous abortions and a healthy child. The initial karyotype showed a small, bisatellited, apparently metacentric marker chromosome, 47,XX,+idic(15)(q11.1), maternally inherited. The proband's mother was mosaic for the idic(15)(q11.1) without pregnancy loss. Reexamination of the proband's karyotype revealed cryptic mosaicism for 1 ring and 1 minute chromosome derived de novo from chromosome 9 in 2% of the metaphases. In FISH analysis, the patient's karyotype was mos 47,XX,+idic(15)(q11.1)mat[100]/49,XX,+idic(15)(q11.1)mat,+r(9;9;9;9),+der(9)dn[2]. The second spontaneous abortion had trisomy 9 (47,XX,+9); the third had mosaic trisomy 9 in 21% of the nuclei and isodicentric chromosome 15 in 36% of the nuclei (mos 48,XN,+9,+idic(15)(q11.1)/47,XN,+9/47,XN,+idic(15)(q11.1)/46,XN). The first and fourth abortions were not cytogenetically studied. The cause of the spontaneous abortions in this patient is likely the cryptic mosaicism for ring and minute chromosomes 9, and gonadal mosaicism is most probable, due to the 2 abortions.
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http://dx.doi.org/10.1159/000494822DOI Listing
February 2019

A mosaic intragenic microduplication of LAMA1 and a constitutional 18p11.32 microduplication in a patient with keratosis pilaris and intellectual disability.

Am J Med Genet A 2018 11 23;176(11):2395-2403. Epub 2018 Sep 23.

Laboratory of Cytogenetics, Research Institute of Medical Genetics, Tomsk NRMC, Tomsk, Russia.

The application of array-based comparative genomic hybridization and next-generation sequencing has identified many chromosomal microdeletions and microduplications in patients with different pathological phenotypes. Different copy number variations are described within the short arm of chromosome 18 in patients with skin diseases. In particular, full or partial monosomy 18p has also been associated with keratosis pilaris. Here, for the first time, we report a young male patient with intellectual disability, diabetes mellitus (type I), and keratosis pilaris, who exhibited a de novo 45-kb microduplication of exons 4-22 of LAMA1, located at 18p11.31, and a 432-kb 18p11.32 microduplication of paternal origin containing the genes METTL4, NDC80, and CBX3P2 and exons 1-15 of the SMCHD1 gene. The microduplication of LAMA1 was identified in skin fibroblasts but not in lymphocytes, whereas the larger microduplication was present in both tissues. We propose LAMA1 as a novel candidate gene for keratosis pilaris. Although inherited from a healthy father, the 18p11.32 microduplication, which included relevant genes, could also contribute to phenotype manifestation.
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http://dx.doi.org/10.1002/ajmg.a.40478DOI Listing
November 2018

Karyotype of the blastocoel fluid demonstrates low concordance with both trophectoderm and inner cell mass.

Fertil Steril 2018 06;109(6):1127-1134.e1

Cytogenetics Laboratory, Research Institute of Medical Genetics, Tomsk National Research Medical Center of Russian Academy of Sciences, Tomsk, Russian Federation; Department of Medical Genetics, Siberian State Medical University, Tomsk, Russian Federation.

Objective: To compare the genomic profiles of blastocoel fluid (BF), inner cell mass (ICM), and trophectoderm (TE) cells derived from the same blastocyst.

Design: Prospective study.

Setting: Academic and in vitro fertilization units.

Patient(s): Sixteen donated cryopreserved embryos at blastocyst stage.

Intervention(s): BF, TE, and ICM cells were retrieved from each blastocyst for chromosome analysis by means of next-generation sequencing (NGS).

Main Outcome Measure(s): Aneuploidy screening and assessment of mosaicism in BF, TE and ICM samples with subsequent comparison of genomic profiles between the three blastocyst compartments.

Result(s): Out of 16 blastocysts, 10 BF samples and 14 TE and ICM samples provided reliable NGS data for comprehensive chromosome analysis. Only 40.0% of BF-DNA karyotypes were fully concordant with TE or ICM, compared with 85.7% concordance between TE and ICM. In addition, BF-DNA was burdened with mosaic aneuploidies and the total number of affected chromosomes in BF was significantly higher compared with the TE and ICM.

Conclusion(s): BF-DNA can be successfully amplified and subjected to NGS, but owing to increased discordance with ICM and TE, BF does not adequately represent the status of the rest of the embryo. To overcome biologic and technical challenges associated with BF sampling and processing, blastocentesis would require improvement in both laboratory protocols and aneuploidy calling algorithms. Therefore, TE biopsy remains the most effective way to predict embryonic karyotype, and the use of BF as a single source of DNA for preimplantation genetic screening is not yet advised.
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http://dx.doi.org/10.1016/j.fertnstert.2018.02.008DOI Listing
June 2018

Compound phenotype in a girl with r(22), concomitant microdeletion 22q13.32-q13.33 and mosaic monosomy 22.

Mol Cytogenet 2018 27;11:26. Epub 2018 Apr 27.

1Research Institute of Medical Genetics, Tomsk NRMC, Tomsk, Russia.

Background: Ring chromosome instability may influence a patient's phenotype and challenge its interpretation.

Results: Here, we report a 4-year-old girl with a compound phenotype. Cytogenetic analysis revealed her karyotype to be 46,XX,r(22). aCGH identified a 180 kb 22q13.32 duplication, a 2.024 Mb subtelomeric 22q13.32-q13.33 deletion, which is associated with Phelan-McDermid syndrome, and a maternal single gene 382-kb deletion of uncertain clinical significance located in the region of the 3q13.31 deletion syndrome. All chromosomal aberrations were confirmed by real-time PCR in lymphocytes and detected in skin fibroblasts. The deletions were also found in the buccal epithelium. According to FISH analysis, 8% and 24% of the patient's lymphocytes and skin fibroblasts, respectively, had monosomy 22.

Conclusions: We believe that a combination of 22q13.32-q13.33 deletion and monosomy 22 in a portion of cells can better define the clinical phenotype of the patient. Importantly, the presence of monosomic cells indicates ring chromosome instability, which may favor karyotype correction that is significant for the development of chromosomal therapy protocols.
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http://dx.doi.org/10.1186/s13039-018-0375-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5923029PMC
April 2018

Allele-Specific Biased Expression of the CNTN6 Gene in iPS Cell-Derived Neurons from a Patient with Intellectual Disability and 3p26.3 Microduplication Involving the CNTN6 Gene.

Mol Neurobiol 2018 Aug 11;55(8):6533-6546. Epub 2018 Jan 11.

Institute of Cytology and Genetics SB RAS, Novosibirsk, 630090, Russia.

Copy number variations (CNVs) of the human CNTN6 gene caused by megabase-scale microdeletions or microduplications in the 3p26.3 region are often the cause of neurodevelopmental disorders, including intellectual disability and developmental delay. Surprisingly, patients with different copy numbers of this gene display notable overlapping of neuropsychiatric symptoms. The complexity of the study of human neuropathologies is associated with the inaccessibility of brain material. This problem can be overcome through the use of reprogramming technologies that permit the generation of induced pluripotent stem (iPS) cells from fibroblasts and their subsequent in vitro differentiation into neurons. We obtained a set of iPS cell lines derived from a patient carrier of the CNTN6 gene duplication and from two healthy donors. All iPS cell lines displayed the characteristics of pluripotent cells. Some iPS cell lines derived from the patient and from healthy donors were differentiated in vitro by exogenous expression of the Ngn2 transcription factor or by spontaneous neural differentiation of iPS cells through the neural rosette stage. The obtained neurons showed the characteristics of mature neurons as judged by the presence of neuronal markers and by their electrophysiological characteristics. Analysis of allele-specific expression of the CNTN6 gene in these neuronal cells by droplet digital PCR demonstrated that the level of expression of the duplicated allele was significantly reduced compared to that of the wild-type allele. Importantly, according to the sequencing data, both copies of the CNTN6 gene, which were approximately 1 Mb in size, showed no any additional structural rearrangements.
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http://dx.doi.org/10.1007/s12035-017-0851-5DOI Listing
August 2018

Clinically relevant morphological structures in breast cancer represent transcriptionally distinct tumor cell populations with varied degrees of epithelial-mesenchymal transition and CD44CD24 stemness.

Oncotarget 2017 Sep 19;8(37):61163-61180. Epub 2017 May 19.

Department of General and Molecular Pathology, Cancer Research Institute, Tomsk National Research Medical Center, Russian Academy of Sciences, 634050, Tomsk, Russian Federation.

Intratumor morphological heterogeneity in breast cancer is represented by different morphological structures (tubular, alveolar, solid, trabecular, and discrete) and contributes to poor prognosis; however, the mechanisms involved remain unclear. In this study, we performed 3D imaging, laser microdissection-assisted array comparative genomic hybridization and gene expression microarray analysis of different morphological structures and examined their association with the standard immunohistochemistry scorings and CD44CD24 cancer stem cells. We found that the intratumor morphological heterogeneity is not associated with chromosomal aberrations. By contrast, morphological structures were characterized by specific gene expression profiles and signaling pathways and significantly differed in progesterone receptor and Ki-67 expression. Most importantly, we observed significant differences between structures in the number of expressed genes of the epithelial and mesenchymal phenotypes and the association with cancer invasion pathways. Tubular (tube-shaped) and alveolar (spheroid-shaped) structures were transcriptionally similar and demonstrated co-expression of epithelial and mesenchymal markers. Solid (large shapeless) structures retained epithelial features but demonstrated an increase in mesenchymal traits and collective cell migration hallmarks. Mesenchymal genes and cancer invasion pathways, as well as Ki-67 expression, were enriched in trabecular (one/two rows of tumor cells) and discrete groups (single cells and/or arrangements of 2-5 cells). Surprisingly, the number of CD44CD24 cells was found to be the lowest in discrete groups and the highest in alveolar and solid structures. Overall, our findings indicate the association of intratumor morphological heterogeneity in breast cancer with the epithelial-mesenchymal transition and CD44CD24 stemness and the appeal of this heterogeneity as a model for the study of cancer invasion.
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http://dx.doi.org/10.18632/oncotarget.18022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5617414PMC
September 2017

Genomic structural variations for cardiovascular and metabolic comorbidity.

Sci Rep 2017 01 25;7:41268. Epub 2017 Jan 25.

Laboratory of Population Genetics, Research Institute of Medical Genetics, Tomsk National Research Medical Center, Russian Academy of Sciences, Tomsk, Russia.

The objective of this study was to identify genes targeted by both copy number and copy-neutral changes in the right coronary arteries in the area of advanced atherosclerotic plaques and intact internal mammary arteries derived from the same individuals with comorbid coronary artery disease and metabolic syndrome. The artery samples from 10 patients were screened for genomic imbalances using array comparative genomic hybridization. Ninety high-confidence, identical copy number variations (CNVs) were detected. We also identified eight copy-neutral changes (cn-LOHs) > 1.5 Mb in paired arterial samples in 4 of 10 individuals. The frequencies of the two gains located in the 10q24.31 (ERLIN1) and 12q24.11 (UNG, ACACB) genomic regions were evaluated in 33 paired arteries and blood samples. Two patients contained the gain in 10q24.31 (ERLIN1) and one patient contained the gain in 12q24.11 (UNG, ACACB) that affected only the blood DNA. An additional two patients harboured these CNVs in both the arteries and blood. In conclusion, we discovered and confirmed a gain of the 10q24.31 (ERLIN1) and 12q24.11 (UNG, ACACB) genomic regions in patients with coronary artery disease and metabolic comorbidity. Analysis of DNA extracted from blood indicated a possible somatic origin for these CNVs.
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http://dx.doi.org/10.1038/srep41268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5264603PMC
January 2017

A de novo microtriplication at 4q21.21-q21.22 in a patient with a vascular malignant hemangioma, elongated sigmoid colon, developmental delay, and absence of speech.

Am J Med Genet A 2016 08 10;170(8):2089-96. Epub 2016 Jun 10.

Institute of Medical Genetics, Tomsk, Russia.

The widespread application of array comparative genomic hybridization (aCGH) has provided new insights into the clinical significance of copy number variations (CNVs) in the human genome. Many microdeletion syndromes have recently been linked to corresponding reciprocal microduplication syndromes related to CNVs in the same chromosomal regions. However, the extent of CNVs may not be restricted to only microduplications but may also include microtriplications or even quadruplications. 4q21 microdeletion syndrome is one of these recently described syndromes. The phenotype includes growth restriction, neonatal hypotonia, severe developmental delay, absent or delayed speech, and distinct facial features. The minimal critical deleted region, which is 1.3 Mb in size, contains the PRKG2, RASGEF1B, HNRNPD, HNRPDL, and ENOPH1 genes. Here, we report a 5.4-year-old girl with developmental delay, absence of speech, muscular hypertension, macrocephaly, a broad forehead, frontal bossing, relatively elongated extremities, a vascular malignant hemangioma in anamnesis, and elongated sigmoid colon. aCGH revealed a microtriplication at 4q21.21-q21.22 that was 1.61 Mb in size. This de novo microtriplication included nine genes (BMP3, PRKG2, RASGEF1B, HNRNPD, HNRPDL, ENOPH1, TMEM150C, LINC00575, and SCD5) and overlapped with the minimal critical region for 4q21 microdeletion syndrome. Some clinical features of the patient were similar to those of 4q21 microdeletion (macrocephaly, frontal bossing, developmental delay, absence of speech, and anxiety), whereas others were mirrored (elongated extremities and muscular hypertension). The first identified case of a de novo microtriplication at 4q21.21-q21.22 emphasizes the clinical significance of CNVs at 4q21 for patients with developmental delay and absence of speech. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37754DOI Listing
August 2016

Comparative Cytogenetic Analysis of Spontaneous Abortions in Recurrent and Sporadic Pregnancy Losses.

Biomed Hub 2016 Jan-Apr;1(1):1-11. Epub 2016 Apr 27.

Laboratory of Cytogenetics, Institute of Medical Genetics, Siberian State Medical University, Tomsk, Russia.

Background: The majority of miscarriages are sporadic; however, 1-5% of couples experience recurrent pregnancy loss (RPL). Approximately 50-60% of miscarriages result from chromosomal abnormalities. Currently, there are conflicting reports regarding the rates of chromosomal abnormalities between recurrent and sporadic pregnancy losses.

Methods: A retrospective comparative cytogenetic analysis of 442 RPL and 466 sporadic abortions (SA) was performed. Maternal age and medical background were evaluated, and chromosomal abnormality rates were compared between groups.

Results: The frequency of embryos with abnormal karyotypes was significantly higher in SA compared to RPL (56.7 and 46.6%, respectively), and abortions from women under 30 years of age were the main contributor to this difference. An age-dependent increase in the abnormal karyotype rate was observed in two groups of women - those with SA [53.0 and 70.1% for younger and older (≥35-year-old) mothers, respectively] and those with idiopathic RPL without any concomitant reproductive pathology (46.5 and 78.4% for younger and older mothers) - but not in the group of women with RPL associated with concomitant reproductive pathology. The incidence of recurrent abnormal karyotypes in subsequent miscarriages was significantly higher than random probability (odds ratio = 22.75).

Conclusion: Our findings highlight the variability in the risk of aneuploidy in recurrent abortion.
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http://dx.doi.org/10.1159/000446099DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6945958PMC
April 2016

Relationship between morphological and cytogenetic heterogeneity in invasive micropapillary carcinoma of the breast: a report of one case.

J Clin Pathol 2015 Sep 15;68(9):758-62. Epub 2015 Jun 15.

Department of Pathological Anatomy and Cytology, Tomsk Cancer Research Institute, Tomsk, Russian Federation Department of Pathological Anatomy, Siberian State Medical University, Tomsk, Russian Federation.

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http://dx.doi.org/10.1136/jclinpath-2015-203009DOI Listing
September 2015

A comparison of genome-wide DNA methylation patterns between different vascular tissues from patients with coronary heart disease.

PLoS One 2015 9;10(4):e0122601. Epub 2015 Apr 9.

Laboratory of Population Genetics, Research Institute of Medical Genetics, Tomsk, Russian Federation; Laboratory of Human Ontogenetics, Tomsk State University, Tomsk, Russian Federation.

Epigenetic mechanisms of gene regulation in context of cardiovascular diseases are of considerable interest. So far, our current knowledge of the DNA methylation profiles for atherosclerosis affected and healthy human vascular tissues is still limited. Using the Illumina Infinium Human Methylation27 BeadChip, we performed a genome-wide analysis of DNA methylation in right coronary artery in the area of advanced atherosclerotic plaques, atherosclerotic-resistant internal mammary arteries, and great saphenous veins obtained from same patients with coronary heart disease. The resulting DNA methylation patterns were markedly different between all the vascular tissues. The genes hypomethylated in athero-prone arteries to compare with atherosclerotic-resistant arteries were predominately involved in regulation of inflammation and immune processes, as well as development. The great saphenous veins exhibited an increase of the DNA methylation age in comparison to the internal mammary arteries. Gene ontology analysis for genes harboring hypermethylated CpG-sites in veins revealed the enrichment for biological processes associated with the development. Four CpG-sites located within the MIR10B gene sequence and about 1 kb upstream of the HOXD4 gene were also confirmed as hypomethylated in the independent dataset of the right coronary arteries in the area of advanced atherosclerotic plaques in comparison with the other vascular tissues. The DNA methylation differences observed in vascular tissues of patients with coronary heart disease can provide new insights into the mechanisms underlying the development of pathology and explanation for the difference in graft patency after coronary artery bypass grafting surgery.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122601PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4391864PMC
December 2015

Single gene microdeletions and microduplication of 3p26.3 in three unrelated families: CNTN6 as a new candidate gene for intellectual disability.

Mol Cytogenet 2014 31;7(1):97. Epub 2014 Dec 31.

Laboratory of Cytogenetics, Institute of Medical Genetics, 10 Nab. Ushaiki, 634050 Tomsk, Russia ; Department of Medical Genetics, Siberian State Medical University, Tomsk, Russia.

Background: Detection of submicroscopic chromosomal alterations in patients with a idiopathic intellectual disability (ID) allows significant improvement in delineation of the regions of the genome that are associated with brain development and function. However, these chromosomal regions usually contain several protein-coding genes and regulatory elements, complicating the understanding of genotype-phenotype correlations. We report two siblings with ID and an unrelated patient with atypical autism who had 3p26.3 microdeletions and one intellectually disabled patient with a 3p26.3 microduplication encompassing only the CNTN6 gene.

Results: Two 295.1-kb microdeletions and one 766.1-kb microduplication of 3p26.3 involving a single gene, CNTN6, were identified with an Agilent 60K array. Another 271.9-kb microdeletion of 3p26.3 was detected using an Affymetrix CytoScan HD chromosome microarray platform. The CHL1 and CNTN4 genes, although adjacent to the CNTN6 gene, were not affected in either of these patients.

Conclusions: The protein encoded by CNTN6 is a member of the immunoglobulin superfamily and functions as a cell adhesion molecule that is involved in the formation of axon connections in the developing nervous system. Our results indicate that CNTN6 may be a candidate gene for ID.
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http://dx.doi.org/10.1186/s13039-014-0097-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4299808PMC
January 2015

Array CGH analysis of a cohort of Russian patients with intellectual disability.

Gene 2014 Feb 27;536(1):145-50. Epub 2013 Nov 27.

Institute of Medical Genetics, Tomsk, Russia.

The use of array comparative genomic hybridization (array CGH) as a diagnostic tool in molecular genetics has facilitated the identification of many new microdeletion/microduplication syndromes (MMSs). Furthermore, this method has allowed for the identification of copy number variations (CNVs) whose pathogenic role has yet to be uncovered. Here, we report on our application of array CGH for the identification of pathogenic CNVs in 79 Russian children with intellectual disability (ID). Twenty-six pathogenic or likely pathogenic changes in copy number were detected in 22 patients (28%): 8 CNVs corresponded to known MMSs, and 17 were not associated with previously described syndromes. In this report, we describe our findings and comment on genes potentially associated with ID that are located within the CNV regions.
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http://dx.doi.org/10.1016/j.gene.2013.11.029DOI Listing
February 2014

A mathematical model for evaluation of maternal cell contamination in cultured cells from spontaneous abortions: significance for cytogenetic analysis of prenatal selection factors.

Fertil Steril 2005 Apr;83(4):964-72

Cytogenetics Laboratory, Institute of Medical Genetics, Tomsk Scientific Center, Russian Academy of Medical Sciences, Ushaika Street 10, Tomsk 634050, Russia.

Objective: To develop a mathematical model for more precise estimation of the incidence of chromosomal abnormalities and the sex ratio among spontaneous abortions masked by maternal cell contamination.

Design: Retrospective analysis.

Setting: Academic medical center.

Patient(s): One hundred twelve samples of spontaneous abortion with a "46,XX" karyotype and 97 parents with aborted embryos.

Intervention(s): The presence of Y chromosome DNA in native tissues of "46,XX" spontaneous abortions was detected by amelogenin locus analysis. Detection of aneuploidies in noncultured tissues of "46,XX" abortions was performed by microsatellite DNA analysis and confirmed by fluorescence in situ hybridization.

Main Outcome Measure(s): Accuracy of cytogenetic evaluation of spontaneous abortions.

Result(s): Y chromosome DNA was revealed in 16% of the embryos with a "46,XX" karyotype. According to the mathematical model proposed, the frequency of chromosomal abnormalities in a sample of 478 abortions increased from 54.6% to 60.3%, and the sex ratio in embryos with normal karyotype changed from 0.66 to 1.02. The experimental validation of the model has shown that the observed and expected incidences of chromosomal abnormalities in "46,XX" abortions were in good agreement.

Conclusion(s): Maternal cell contamination clearly affects the incidence of registered chromosomal abnormalities and the sex ratio in spontaneous abortions. Correction for maternal cell contamination should be taken into account before invoking biological explanations of sex ratio bias and might be useful to include in diagnostic reporting.
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http://dx.doi.org/10.1016/j.fertnstert.2004.12.009DOI Listing
April 2005

Features of chromosomal abnormalities in spontaneous abortion cell culture failures detected by interphase FISH analysis.

Eur J Hum Genet 2004 Jul;12(7):513-20

Cytogenetics Laboratory, Institute of Medical Genetics, Tomsk Scientific Centre, Russian Academy of Medical Sciences, 634050 Tomsk, Russia.

Cytogenetic analysis of reproductive wastage is an important stage in understanding the genetic background of early embryogenesis. The results of conventional cytogenetic studies of spontaneous abortions depend on tissue culturing and are associated with a significant cell culture failure rate. We performed interphase dual-colour FISH analysis to detect chromosomal abnormalities in noncultured cells from two different tissues-cytotrophoblast and extraembryonic mesoderm-of 60 first-trimester spontaneous abortions from which cells had failed to grow in culture. An original algorithm was proposed to optimize the interphase karyotype screening with a panel of centromere-specific DNA probes for all human chromosomes. The overall rate of numerical chromosomal abnormalities in these cells was 53%. Both typical and rare forms of karyotype imbalance were found. The observation of six cases (19%) of monosomy 7, 15, 21 and 22 in mosaic form, with a predominant normal cell line, was the most unexpected finding. Cell lines with monosomies 21 and 22 were found both in cytotrophoblast and mesoderm, while cells with monosomy 7 and 15 were confined to the cytotrophoblast. The tissue-specific compartmentalization of cell lines with autosomal monosomies provides evidence that the aneuploidy of different human chromosomes may arise during different stages of intrauterine development. The effect of aneuploidy on selection may differ, however, depending on the specific chromosome. The abortions also revealed a high frequency of intratissue chromosomal mosaicism (94%), in comparison with that detected by conventional cytogenetic analysis (29%; P<0.001). Confined placental mosaicism was found in 25% of the embryos. The results of molecular cytogenetic analysis of these cell culture failures illustrate that the diversity and phenotypic effects of chromosomal abnormalities during the early stages of human development are underestimated.
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http://dx.doi.org/10.1038/sj.ejhg.5201178DOI Listing
July 2004