Validation of new variants identified in primer immune deficiency patients

Primary immunodeficiencies (PID) are a group of diseases that consist over 130 different diseases which influence function, development or both of the immune system. The PID phenotypes each fall into the rare disease group and have a prevalence of approximately 1:10000 live births. However, a higher rate is observed in populations where consanguineous marriage is high or genetically isolated populations such as Turkey. In the most cases, PIDs are monogenic diseases that follow a Mendelian princibles of inheritance. Diagnosis of PID is delayed due to the wide phenotypic variability of the disease. For this reason, immunological and genetic tests are of great importance in determining the molecular disorders underlying primary immune deficiency syndromes. In previous studies of our group, known and unknown gene variations were detected by next generation sequencing-based gene panels and exome analyzes in PID patients. Within the scope of this thesis, the detected variations were verified with Sanger sequencing in the indeks case and familial segregation was shown, and predicting possible damage (protein, splice site, etc.) quantitative PCR and protein expression (Western blot, flow cytometry, ELISA) were investigated. In this thesis, two of the six variations/genes studied could not be confirmed by Sanger sequencing. For the remaining four variants/genes, the function of at least one method has been studied. As a result of the study based on the expression analysis of the variant detected in the RAG2 gene, its expression was found to be decreased compared to healthy individuals. In addition to this variant, another gene has been identified that explains the lymphoma findings in the patient. The study will be continued with further functional analysis. A new candidate gene for the PID phenotype, TM4SF4, was studied to establish the genotype-phenotype relationship with the disease. In the study, the relationship of the variant in the MASP2 gene, which was detected in a patient whose diagnosis could not be made clearly, with the disease was tried to be determined. Knowing the patient- specific genetic changes will guide the clinician in terms of the prognosis of the disease and the treatment approach. Key Words: Primary immunodeficiency, variation, quantitative PCR, flow cytometry, Sanger sequencing.