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CX37, CX40, CX43 AND CX45 GENE EXPRESSION IN DEVELOPING, POSTNATAL AND NEPHROTIC HUMAN KIDNEYS

Connexins (Cx) are gap junction proteins and are mediators of normal kidney development but also play important role in homeostasis of adult kidney tissue. Cx37 is coded by GJA4 gene, Cx40 by gene GJA5, Cx43 by GJA1 and Cx45 is coded by GJC1 gene. Pathological kidney conditions are linked to changes in Cx expression and localisation. The aim of this study was to measure the quantity of Cx37, Cx40, Cx43 and Cx45 in fetal developing stages of the kidney, postnatal kidney tissue and in nephrotic kidney tissue. The expression of Cx37, Cx40, Cx43 and Cx45 was examined by double immunofluorescence on paraffin sections of 8 to 10-, 21 to 22-, 38- week old developing kidney tissue, postnatal 1.5-year old kidney tissue and in nephrotic kidney tissue. Protein expression was quantified in fluorescence intensity units (FIU). FIU represents area under curve of fluorescence intensity histogram, it is a hybrid measure of signal brightness and percentage of area covered by signal on microphotograph. Analyse was performed in ImageJ software and the data were analysed by Welch’s ANOVA and unpaired t-test with Welch’s correction for post-hoc test. In 8-10 weeks and 38 weeks there were significant differences in fluorescence intensity between connexins (P<0.0001). More specifically, in week 8-10 when compared to other connexins Cx43 was least expressed (P<0.0001), whereas other connexins had similar levels of expression. In week 38, Cx45 had the highest level of expression among connexins (P<0.001), whereas Cx43 was the least expressed (P<0.001). In 1, 5 year postnatal kidney Cx40 showed higher expression than other connexins (P<0.01), and Cx37 and Cx45 were the lowest expressed. There were no significant differences in connexin expression in tissue of patients with nephrotic syndrome (P=0.927). Expression of different connexins play an important role in different stages of kidney development.

Cx37, Cx40, Cx43, Cx45, nephrotic kidney, kidney development

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