Current trends in molecular cytogenetics, assisted reproductive technologies and cell reprogramming for the revelation of chromosomal diseases pathogenesis are reviewed.

Pericentric inversion are intrachromosomal balanced structural abnormalities. The frequency in the general population is ranged from about 0.12% to 0.7% [1]. To provide complete synapsis and recombination during meiosis pairing of the normal and inverted chromosomes requires the formation of inversion loop. One crossover within the inversion loop leads to the production of two complementary recombinant chromosomes with both duplicated and deleted chromosome segments including the regions distal to the inversion. The particular clinical relevance of inversion chromosomes is that they can set the stage for the generation of recombinant gametes that may lead to early miscarriages, stillbirth or congenital abnormalities. The estimation of empiric frequencies of recombinant spermatozoa, risk of abnormal gamete formation and potential zygote viability in four pericentric inversion carriers was performed.

The gene expression analysis of iPSC-derived neurons, obtained from patients with idiopathic intellectual disability and reciprocal microdeletion and microduplication in 3p26.3 region affecting the single CNTN6 gene was performed. The global gene expression dysregulation was demonstrated for cells with CNTN6 copy number variation. Gene expression in neurons with CNTN6 copy number changes was downregulated for genes, whose products are involved in the central nervous system development.

Mitotic instability of ring chromosomes can lead to the appearance of cell clones with different genetic structure. IPSCs from fibroblasts of patients with r(8), r(13), r(18), and r(22) were used as a model of ring chromosomes mitotic behavior. Karyotypes of iPSC lines with r(8) and r(18) have so far been evaluated only in the early passages, lines with r(22) have maintained a relatively stable karyotype up to 60 passages. The occurrence of rearrangements and cellular heterogeneity was found characteristic for r(13) iPSCs. The determination of factors affecting the ring chromosomes mitotic stability would be beneficial for the patient’s prognosis.

The concept of meiotic co-orientation of non-homologous chromosomes as a model of meiosis, experimentally confirmed in Drosophila, was proposed in 1971 to explain the interchromosomal effect in humans, but has not received sufficient evidence since. The data of the “non-canonical” behavior of sex chromosomes presented in this article are the basis for recognizing the existence of this phenomenon in human spermatogenesis.

Autosomal reciprocal translocations (ART) lead to an increased risk of imbalanced gametes formation due to pathological meiotic segregation. Segregation type was analyzed and theoretical segregation pattern was determined in 26 cleavage stage embryos in this article. A coincidence of theoretical and detectable segregation types was observed in more than 50 % of blastomeres in 73 % of cases. The data obtained may be used for personalized genetic counseling in families with high risks of recurrent spontaneous abortions, infertility or children with birth defects due to ART.

A skewed X-chromosome inactivation can be a consequence and a marker of impaired cell proliferation in the presence of copy number variations (CNV) on the X chromosome. X-linked CNVs are detected in women with miscarriages and a skewed X-chromosome inactivation (with a frequency of 33.3%), as well as in patients with intellectual disability and skewed X-chromosome inactivation in their mothers (with a frequency of 40%).

We report the results of quality assessment for preparation of cytogenetic slides and chromosomal analysis in the laboratories of Russian Federation in the system of the interlaboratory comparative examinations “FSVOK” in 2018-2019. Common causes of poor results of assessment and the ways for improvement of quality for cytogenetic investigations are discussed.

The identification of chromosomal abnormalities at the submicroscopic level and the establishment of their role in the etiology of intellectual disorders are an important scientific and practical task. Evaluation of the pathogenic value of the less studied type of copy number variation - chromosomal microduplication - is an actual issue. The study proposed an algorithm for interpreting the clinical significance of partial trisomies, which is an integral component in the diagnosis and prevention of chromosomal diseases.

We developed and applied for patients with ring chromosomes an algorithm for molecular cytogenetic diagnostics which includes, in addition to the standard karyotyping, array comparative genomic hybridization (aCGH), real-time PCR, and fluorescence in situ hybridization (FISH).

Deletions of the short arm of chromosome 9 are a clinically and genetically heterogeneous group. Most of the cases described are terminal deletions or unbalanced translocations with different break points on the short arm of chromosome 9. Interstitial deletions of the short arm of chromosome 9 are an extremely rare chromosome pathology. We report a patient with developmental and psychomotor delay, cerebellar hypoplasia and hypospadias, who was diagnosed with interstitial 9p24.3-p23 deletion affecting the DMRT1 gene during chromosome microarray analysis (СMA).

We present cases of chromosomal microstructural rearrangements in families with variable phenotypes: microduplication syndrome Xq28 (MECP2) in a girl with typical dismorphic features as a result of an unbalanced translocation between X-chromosome and chromosome 4 inherited from the mother who had a balanced aberration, and DiGeorgy syndrome with variable features in sisters that was inherited from the father carrying a rare balanced structural rearrangement with a marker chromosome.

Сlinical and molecular-genetic study results of a girl with developemental and psychomotor delay, lack of speech development, microcephaly, and pontocerebellar hypoplasia are presented. Chromosomal microarray analysis revealed a deletion of Xp11.4 affecting the CASK gene that is associated with clinical manifestations of MICPCH-syndrome.

Republican Scientific and Practical Centre «Mother and Child», Belarus Reproduction data of 4 inv(9)(p24q32) carriers was presented. Published cases of inv(9)(p24q34.1) and inv(9)(p22q32) carriers were analyzed. Pregnancies outcomes of the patients with large (>50%) chromosome 9 inversions include a miscarriages (our cases) and live born children with combined chromosomal unbalance rec(9)dup(q)/del(p) (published data).

Interchromosomal insertions are rare rearrangements implying the highest reproductive risk. We report a familial case of ins(5;4)(q31;q23q31). Reproductive history was analyzed. It was shown that fetuses with partial trisomy 4q23-q31 are detected. The results of a pathomorphological study of aborted fetuses were presented.

Inverted duplication deletion 8p syndrome (inv dup del(8p), ORPHA 96092) is a rare chromosomal abnormality with a frequency of 1:10,000 - 30,000 newborns. Clinical manifestations of this syndrome include mental retardation, facial anomalies, hypoplasia/agenesis of corpus callosum, scoliosis and/or kyphosis, hypotonia, congenital heart defects. The article presents the clinical and molecular cytogenetic characteristics of two patients with inv dup del (8p) syndrome and clarifies the formation mechanisms.

The results of FISH study of lymphocytes and buccal epithelium of 9 patients with Klinefelter syndrome and azoospermia are presented.

Pregnancy outcomes and results of cytogenetic studies of 50 cases of autosome trisomy karyotype discordance in obtaining a normal karyotype in trophoblast cells or villi mesenchymal stroma are presented.

Comparative molecular karyotyping of cell-free DNA from the blastocoele fluid of the blastocyst and the embryoblast and trophectoderm, allowed us to obtain evidence for the presence of mechanisms of self-correction of the embryonic karyotype at the preimplantation stage of human development.

First-trimester aborted fetuses with abdominal cysts (n=76) have been examined at anatomic-pathological investigation. A final diagnosis included choledochal cyst, duodenal and anorectal atresia, cloacal disgenesis syndrome and megacystis. Besides gastrointestinal atresia and lower urinary tract obstructions heterotaxy and diaphragmatic hernia have been revealed at morphological examination. In total 23,7% of fetal abdominal cysts in the first trimester of gestation were associated with chromosomal abnormalities.

A rare case of trisomy 2 is presented. Prenatally at 18/19 weeks of pregnancy, confirmed by the method of chromosome microarray analysis (arrayCGH) of placental villi.

The first case of prenatal diagnosis of type I oro-facio-digital syndrome (OMIM 311200) in fetus with partial monosomy Xp22.2 is presented. The cause of type I oro-facio-digital syndrome is mutations in the OFDI gene, cases of disease due to chromosomal microdeletions affecting the OFDI gene are rare. Ultrasound examination of the fetus in the second trimester of pregnancy revealed congenital defect of brain development and multiple echographic markers of chromosomal and syndrome pathology. An umbilical cord blood was obtained in 21 weeks of gestation by cordocentesis. aCGH revealed partial monosomy Xp22.2 at 2.6 Mb in size: arr [hg19] Xp22.2(11135472_13798048) × 1. The presence of microdeletion, as well as its de novo origin, was confirmed by the quantitative real time PCR. The use of high-resolution molecular cytogenetic analysis significantly expands the possibilities of syndrome monogenic pathology diagnosis in the prenatal period.

The spread of NIPTs with risk assessment of sex chromosome aberrations has led to an increase in the number of patients requiring genetic counselling for these pathologies. Analysis of factors influencing family reproductive choices is necessary to improve the quality of information provided to families.

Molecular karyotyping in our study showed a 6.4% increase in the detectability of chromosomal aberrations compared to classical cytogenetic methods, but their combined application is necessary to determine and/or clarify the nature of microscopic or submicroscopic anomalies and to identify balanced rearrangements.

Microdeletion and microduplication syndromes are detected in approximately 8% of fetuses with congenital malformations, however, the diagnosis of pathogenic CNVs in the prenatal period, at the moment, is unregulated and often based on the technical capabilities of the laboratory. The thesis presents the result of a study of fetuses that had congenital malformations and / or markers of chromosomal abnormalities, determined by ultrasound, by the method of chromosomal microarray analysis. Using chromosomal microarray analysis in our sample (N = 1048), numerical chromosome abnormalities were detected in 10.3% of the fetuses and pathogenic chromosome imbalance was revealed in 7.4% of the fetuses, which cannot be detected by standard karyotyping. The results of our analysis are consistent with the data of the scientific literature, which demonstrates the greater efficiency of using SNP microarrays in comparison with classical cytogenetic methods.

Study objective is to assess the prevalence and pattern of chromosomal abnormalities (CAs) in products of conception (POC) for the period from 2015 to 2019. Materials and Methods: 2201 samples of POC were studied by the chromosomal microarray analysis. Study Results: CAs were detected in 49.57% of cases, of which aneuploidy, including several chromosomal and mosaic forms, were detected in 79.65%, triploidy - 10.72%, other CAs with possible clinical significance - 8.62%, tetraploidy - 1.01%. Conclusion: chromosomal microarray analysis can be recommended as a routine method for searching of unbalanced CAs in POC.

Widely performed in Russia prenatally first-trimester screening is based on secondary markers of pathology and has limited sensitivity and specificity. The most promising alternative is the use of noninvasive prenatal screening for fetal aneuploidy (NIPS). This study aims to validate the possibility of NIPS usage for obstetric and gynecological care. DNA screening was validated on samples with known results of invasive prenatal diagnostics (N=1134). It was proven that it is possible to store and transport the samples (N=477). We studied plasma aliquot samples after one year of storage (N=70). Factors that can influence the NIPS results were also evaluated: the proportion of fetal DNA, body mass index (BMI), gestational age, mosaicism, and others.

Noninvasive prenatal DNA screening (NIPS) is getting more widespread in clinical practice in Russia and all around the world. The use of shallow whole-genome sequencing for NIPS allows analysis of all chromosome aneuploidies; hence there are large-scale studies only on test performance on common trisomies. This study aimed to analyze the prevalence of «rare» aneuploidies using whole-genome NIPS and pregnancy outcomes in case of a high risk of «rare» aneuploidy. Noninvasive prenatal DNA screening was performed using in house developed protocol. We have analyzed 2061 samples. In 8 cases (0.4%) high-risk of rare trisomy was detected (3 - trisomy 7, 2 - trisomy 8, 1 - trisomy 10, 2 - trisomy 15). We have identified two cases of a high risk of large copy number variations (CNV). For all of the high-risk cases, we have information about pregnancy outcomes. Thereby whole-genome analysis will enable us to get the additional information and reveal pregnancies in need of further observation or testing. Hence there is not enough data for the estimation of sensitivity and specificity of detection of «rare» aneuploidies.

The results of the original technology of non-invasive prenatal screening based on genome-wide fetal DNA (cfDNA) sequencing of the fetus in maternal blood are presented. The main parameters of the technology are characterized and new possibilities for its use are proposed.

Relatively different characteristics of prenatal tests, the opinion of 800 pregnant women undergoing early prenatal screening (EPS) of congenital malformations and chromosomal abnormalities in the fetus was analyzed. The survey will allow you to compare the results with other countries where NIPT is used in the EPS, and to develop our own recommendations.

In the course of analyzing the results of early prenatal combined first-trimester screening (FTS) in Russia for 2018 (Audit-2019) the assessment of the quality of measures, the overall effectiveness and trends in the development of the FTS system in the regions of Russia. They are presented by comparing the calculated main organizational, methodological and integral indicators with international reference values.

Early prenatal screening that includes ultrasound diagnostics, study of serum markers of PAPP-A and β-HCG, audit plays an important role in the prevention of congenital and hereditary diseases. The results of the study were processed with «Astraia». Analysis of the results of early prenatal screening in the Ivanovo region for the period 2013-2019 showed that when screening coverage, on average, 85.3% of pregnant women registered before 14 weeks of gestation, 157 cases of chromosomal pathology and 126 cases of congenital malformations were detected. However, in 55 cases, the diagnosis of fetal chromosomal pathology was not suspected during screening, and the patients were not at risk and gave birth to sick children (all children had trisomy 21). At the same time, in 1/3 of cases (in 19 patients - 34.5%), the risk of trisomy 21 was estimated as intermediate and was in the range from 1:100 to 1:1000, including in 3 women (5.5%) - in the range from 1:100 to 1:300. We suppose that patients with an intermediate risk of fetal chromosomal abnormalities need further examination to verify the diagnosis, and they should be informed about the possibilities of a non-invasive prenatal test.

The software package «Prenatal Screening» has been developed for early prenatal screening of congenital malformations in children in Krasnodar region.

There is high relevance of medical genetics examination and genetic counseling in patients with reproductive pathology.

The current possibilities of a genetic examination of infertile men, as well as indications and diagnostic algorithms for the genetic causes of male infertility associated with various forms of pathozoospermia are presented.

We examined 19 infertile men, carriers of translocations rob (13;14) and rob (13;15). We assume that fertility problems are resulted from spermatogenesis impairment because of meiotic arrest at prophase I stages, that leads to azoospermia or oligoastenoteratozoospermia and male infertility.

Chromosomal abnormalities (CA), including aneuploidy, are one of the causes of spontaneous abortion, infertility, developmental disorders and malformations. One way to evaluate probability of aneuploid zygotes occurrence is the analysis of parental gametes, however, information about the level of aneuploidy in such cells is insufficient. There was evaluated the frequency of aneuploidy compatible with the viability of the zygote in sperm nuclei of 82 phenotypically normal infertile men with normal and impaired spermatogenesis.

FISH-analysis of sperm aneuploidy for chromosomes 13, 18, 21, X and Y was performed fertile normozoospermic men and infertile pathozoospermic men. The frequency of aneuploidy in pathozoospermic men twice exceeds the frequency of aneuploidy among normozoospermic men. A statistically significant difference between these groups was found the frequency of dysomies 13 and 18 (p=0.03 and p=0.01, respectively), nullisomies 13 and 21 (p=0.02 and p=0.03, respectively) and XY dysomy (p=0.01).

The article presents data the CFTR gene variants in Russian men with various forms of pathozoospermia and patients with CBAVD syndrome, and a comparison of the spectrum of genotypes in these groups.

The article presents the results of a survey of men with azoospermia and severe oligozoospermia, with and without microdeletion of the long arm of the Y chromosome, as well as the results of a testicular biopsy. The absence of deletions of the AZF region, the absence of testicular hypoplasia, as well as normal levels of FSH, LH and inhibin B are prognostically favorable criteria for the success of obtaining spermatozoa with a biopsy of testicular tissue for in vitro fertilization (IVF).

Transsexualism is a gender identity disorder with a multifactorial etiology and poor understood pathogenesis. The study presents the results of a comprehensive clinical and genetic examination of 55 patients with transsexualism, cytogenetic data and results of quantitative analysis of gametogenesis are evaluated.