Obesity is a complex disease subject to numerous environmental and genetic influences. Mouse models are frequently used to study this disease, with the fat (FLI) and lean (FHI) selection lines representing one of the best models of polygenic obesity. Within the gene cluster of co-localised cytosolic phospholipases A2 on chromosome 2, comprising the genes Pla2g4b, Pla2g4d, Pla2g4e and Pla2g4f, the gene Pla2g4e was previously identified as a candidate obesity gene. Bioinformatic analyses identified regulatory regions potentially responsible for the differential expression of this gene between the fat and lean mouse lines. The first aim of this master’s thesis was to determine whether DNA sequence variations in selected regions influence the expression of the Pla2g4e gene, for which a luciferase reporter assay was used. Results for the two tested regions did not show statistically significant differences in regulatory activity between the Fat and Lean lines, although a trend in the F1/R1 region suggests a possible allelic effect. The second objective was to analyse the expression patterns of all four co-localised paralogous genes and determine whether they are subject to co-expression. qPCR analysis across a panel of tissues from the J substrain of C57BL/6 mouse line revealed that the colocalized paralogous genes display markedly distinct tissue-specific expression profiles. Spearman correlation analysis showed a statistically significant correlation between the expression profile of Pla2g4b and all three other genes, while correlations between the other gene pairs were not statistically significant. The results support functional divergence of the colocalized paralogs and suggest that the differential expression of Pla2g4e is not merely a consequence of shared regulation of the entire gene cluster but reflects its specific regulatory control.
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