Browsing by Author "Alkšere, Baiba"

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    Exploring the Potential of Exome Sequencing in Idiopathic Azoospermia : A Genetic Burden and Network Analysis Study
    (2023-08-17) Alkšere, Baiba; Puzuka, Agrita; Lazovska, Marija; Vainselbaum, Ninel Miriam; Vasilonoks, Janis Kristaps; Penka, Elvita; Fodina, Violeta; Ērenpreiss, Juris; Department of Biology and Microbiology; Scientific Laboratory of Molecular Genetics
    The purpose of this study was to investigate the linkage of the association of azoospermia phenotype with genetic alterations, involved in genome instability. Male infertility is a multifactorial pathology, and genetic alterations might be the underlying factors in majority of cases of severe male infertility. The recent emergence of next-generation sequencing offers an opportunity to analyze many genes and their interactions at once, and whole-exome sequencing (WES) together with whole-genome sequencing (WGS) was recently suggested for implementation of diagnosis workup in severe infertility cases. However, the reports on WES in conjunction with burden tests and gene network analysis are scarce or lacking in cases of severe male infertility. WES was performed on 21 nonobstructive azoospermia patients. DNA samples were sequenced using the Twist Comprehensive Exome Panel. Genetic burden test was performed with Testing Rare vAriants using Public Data. Protein interactions were investigated with ConsensusPathDB and Cytoscape. For single nucleotide variants and copy number variations (CNV) analysis, samples were analyzed with the Illumina's BaseSpace Variant Interpreter. Genetic variant burden was found elevated in 1,473 genes out of 30,000 known testis expressed genes. Three hundred and two genes with increased loss-of-function (LoF) variant set were present in more than one sample. Overrepresentation analysis with pathway-based set of genes with high variant burden demonstrated 26 pathways. Overrepresentation analysis with protein complex-based gene sets obtained 14 sets, showing the involvement in cell proliferation and DNA repair. Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) network analysis with Cytoscape identified two clusters: (1) genes, involved in DNA binding/condensation and repair processes and (2) genes with the role in ribosome biosynthesis and gene expression processes. Increased loss of function germline variant burden and sumoylation may have critical significance in spermatogenesis. These parameters may be used for focused diagnosis in nonobstructive azoospermia patients. This may have both general significance for the decreased organism functionality but in particular is critical in spermatogenesis.
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    Performance comparison of two whole genome amplification techniques in frame of multifactor preimplantation genetic testing
    (2018-08-01) Volozonoka, Ludmila; Perminov, Dmitry; Korņejeva, Liene; Alkšere, Baiba; Novikova, Natālija; Pīmane, Evija Jokste; Blumberga, Arita; Kempa, Inga; Miskova, Anna; Gailīte, Linda; Fodina, Violeta; Scientific Laboratory of Molecular Genetics; Department of Obstetrics and Gynaecology
    Purpose: To compare multiple displacement amplification and OmniPlex whole genome amplification technique performance during array comparative genome hybridization (aCGH), Sanger sequencing, SNaPshot and fragment size analysis downstream applications in frame of multifactor embryo preimplantation genetic testing. Methods: Preclinical workup included linked short tandem repeat (STR) marker selection and primer design for loci of interest. It was followed by a family haplotyping, after which an in vitro fertilization preimplantation genetic testing (IVF-PGT) cycle was carried out. A total of 62 embryos were retrieved from nine couples with a confirmed single gene disorder being transmitted in their family with various inheritance traits—autosomal dominant (genes—ACTA2, HTT, KRT14), autosomal recessive (genes—ALOX12B, TPP1, GLB1) and X-linked (genes—MTM1, DMD). Whole genome amplification (WGA) for the day 5 embryo trophectoderm single biopsies was carried out by multiple displacement amplification (MDA) or polymerase chain reaction (PCR)-based technology OmniPlex and was used for direct (Sanger sequencing, fragment size analysis, SNaPshot) and indirect mutation assessment (STR marker haplotyping), and embryo aneuploidy testing by array comparative genome hybridization (aCGH). Results: Family haplotyping revealed informative/semi-informative microsatellite markers for all clinical cases for all types of inheritance. Indirect testing gave a persuasive conclusion for all embryos assessed, which was confirmed through direct testing. The overall allele dropout (ADO) rate was higher for PCR-based WGA, and MDA shows a better genomic recovery scale. Five euploid embryos were subjected to elective single embryo transfer (eSET), which resulted in four clinical pregnancies and birth of two healthy children, which proved free of disease causative variants running in the family postnataly. Conclusions: A developed multifactor PGT protocol can be adapted and applied to virtually any genetic condition and is capable of improving single gene disorder preimplantation genetic testing in a patient-tailored manner thus increasing pregnancy rates, saving costs and increasing patient reliability.