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The GLUT9 transporter, coded by the SLC2A9 gene, is one of the key proteins enabling the trasnfer of uric acid across the membrane in epithelial cells of the proximal tubule. In humans, this protein is naturally expressed in two variants: long (GLUT9L) and short (GLUT9S), which differ from one another by their N-terminus sequence. Each of these isoforms is localized on a different pole of the epithelial cell. The signal sequence/motif responsible for this difference is presumed to be located in the aforementioned N-terminus domain. Numerous allelic variants influencing the transport properties of the protein have also been described. The first aim of this thesis is to verify the influence of a newly discovered variant, characterized by substituting of valine for leucine in the 114th position (V114L, in the short form its corresponding variant V85L) on the ability to transport uric acid. Second aim is to verify the influence of mutations in selected motifs, which could be responsible for the localization of the protein, thus also changing its transport properties. Two dileucine motifs 12LGL14 and 33LL34 and one tyrosine motif 84YIKA87 were tested. Functional studies using 14 C radiolabeled urate demonstrated significant decrease of transport ability for the V114L/V85L allelic variant in both...

Nephrotic syndrome is a kidney disease caused by injury of the podocytes. It can be secondary due to infection, systemic disease or certain drugs, but it may also present as sudden primary nephrotic syndrome without obvious inducer. Current standard treatment has many severe adverse effects. In some patients that are resistant to the initial several-week-long glucocorticoid treatment it is possible to reveal the causative genetic aetiology of the disease, whereas in the rest of them aetiology remains unknown. Those who respond well to initial glucocorticoid treatment and achieve remission may later on develop repeated relapses requiring long-term glucocorticoid therapy. This work describes our original research studies focusing on the improvement of genetic diagnostics of nephrotic syndrome, on the exploration of molecular mechanisms of the second most common genetic cause of the steroid-resistant nephrotic syndrome (transcription factor WT1 mutants) and on the search of clinical and laboratory factors that could predict the resistence to glucocorticoid treatment. By combining Sanger and next-generation sequencing (NGS) we were the first to identify monogenic cause in 38 % of Czech and Slovak children with steroid-resistant nephrotic syndrome whose samples had been collected for 18 years. The most...