Varijante kodirajućih i nekodirajućih regiona gena uzročnika dijabetesa adultnog tipa kod mladih kao modulatori fenotipa i regulatori genske ekspresije

Abstract

Dijabetes adultnog tipa kod mladih (MODY) je nasledni, autozomno dominantni oblik dijabetesa, klinički i genetički veoma heterogen, koji nastaje kao posledica primarne disfunkcije β-ćelija pankreasa. MODY nastaje usled genetičkih varijanti u jednom od brojnih gena asociranih sa MODY dijabetesom, te je metodom sekvenciranja nove generacije i metodom istovremenog umnožavanja vezanih proba, prvi put u Srbij, analizirano 13 gena uzročnika MODY dijabetesa kod 29 klinički suspektnih pedijatrijskih pacijenata. Kombinovanjem ove dve metode detektovano je 20 različitih varijanti kod 75,9% pacijenata u 4 različita gena. Varijante u dva gena, GCK i HNF1B, detekotvane redom, kod 50% i 22,7% pacijenata, predstavljale su glavne uzročnike MODY dijabetesa u ovoj grupi pacijenata. U ovoj studiji identifikovana je i jedna nova prethodno neprijavljena varijanta u GCK genu, c.596T>C; p.Val199Ala, za koju su in silico predikcije nedvosmisleno pokazale da je patogena. Kako bi se detektovale varijante u promotorskom regionu, koje takođe dovode do MODY dijabetesa, analizirani su promotorski regioni četiri najčešća gena uzročnika MODY dijabetesa. Varijantni set u promotrskom regionu GCK gena (−282C>T; −194A>G; 402C>G) i varijanta c.-154-160insTGGGGGT u promotoru HNF1A gena, odabrane su kako bi se u funkcionalnim esejima u ćelijskoj kulturi ispitao njihov uticaj na ekspresiju datih gena. Analizirane su i interakcije ovih potencijalnih regulatornih elemenata sa transkripcionim faktorima u esejima usporene elektroforetske pokretljivosti. Rezultati funkcionalne analize odabarnih promotorskih varijanti ukazali su da varijante u promotoru, osim potencijalno patogenog efekta, mogu da imaju i ulogu modifikatora fenotipa, čime su dopunjena postojeća znanja o varijantama u promotorima MODY gena.

Maturity-onset diabetes of the young (MODY) is an inherited, autosomal dominant form of diabetes, clinically and genetically very heterogeneous, resulting from primary β-cell dysfunction. Since MODY diabetes is caused by single gene variants in one of the many MODY-related genes, next generation sequencing and multiplex ligation-dependent probe amplification analysis were used to analyze 13 MODY-relate genes in 29 clinically suspected pediatric patients, for the first time in Serbia. Combining these two methods, 20 different variants, found in 4 genes, were identified in 75.9% patients. Variants in the GCK and HNF1B gene, detected in 50% and 22.7% patients, respectively, were the main cause of MODY diabetes in our patients. Also, a novel variant in the GCK gene: c.596T>C, p.Val199Ala was identified and predicted to be pathogenic by in silico algorithms. Due to the fact that promoter variants can also lead to MODY diabetes, promoter regions of the four most common MODY genes were screened. Two variants, the variant set in the promoter region of the GCK gene (−282C>T; −194A>G; 402C>G), and the variant c.-154-160insTGGGGGT in the promoter of the HNF1A gene, were selected to analyze their effect on gene expression in functional cell culture studies. Also, electrophoretic mobility shift assay was carried out to investigate the interaction of potential transcription factors with the promoter region surrounding the variant, as well as whether the variants affect the binding of those transcription factors. The results of the functional analysis of the selected promoter variants indicated that variants in the promoter, in addition to potentially pathogenic effect, may also play the role of a phenotype modifier, thus supplementing the existing knowledge about variants in the promoters of MODY genes.