Cytogenetic analyses and sequencing of exon 2 and 3 of Calcium Sensing Receptor (CaSR) gene in sagliker syndrome patients

Chronic kidney disease, as a patho-physiological process, is characterized by declining number of functioning nephrons in the course of time and frequently develops to end stage kidney failure. Some patients suffering from chronic kidney disease develop sagliker syndrome. Sagliker syndrome patients, in addition suffering from kidney disease, develop seconder hyperparathyroidism and serious facial deformities and also they suffer from psychological problems and depression. In these patients, as laboratory findings, hypocalcemia and hyperphosphatemia also develop.In chronic kidney disease patients, having bad prognosis (turning into Sagliker syndrome), it is plausible to think that they are genetically predisposed. In this study, keeping in mind that it could be a genetic predisposition factor and also because of CaSR protein is critically important for calcium homeostasis in the body, exons 2 and 3 of CaSR coding gene sequenced. CaSR, consisted of 1078 amino acid, is a receptor which functions via G protein and a member of seven times membrane spanning protein super family (C family). CaSR is expressed predominantly by parathyroid gland cells, thyroid C cells and kidney. CaSR gene is localized on chromosome 3q13.3-21 region, consisted of 103 kb and 8 exons.In this study, exon 2 and 3 of CaSR gene of 23 patients were sequenced. For exon 2, 3 patients had adenin base deletion at the position of 70239. Two patients had A>G heterozygote alteration at the position of 70471 and also 1 patients had T>C heterozygote alteration at the position of 70622. For exon 3, G>A homozygote alteration at the position of 73724 was detected in 11 patients and also G>A heterozygote alteration at the position of 73724 was detected in 1 patient. For exon 2, at the position of 70622 T altered to C and finally codon TTT altered to codon TTC, both of which coding phenylalanine amino acid, resulting in no protein sequence alteration. According our findings, there is no any relation between etiology and progression of sağlıker syndrome and nucleotide alterations we found in exon 2 and 3 of CaSR gene.In the scope of our study, we also did karyotype analysis of 23 sagliker syndrome patients and 23 control cases. 5 out of 23 patients (21.8%), four male and one female, had normal karyotype in all metaphase plaques. Remainder 18 patients (%78.2) had structural or numerical chromosomal abnormalities at least in one metaphase plaque or more. Important structural chromosome abnormalities, we found are related to chromosomes 2, 4, 5, 6, 7, 9, 10, 11, 13, X and Y. These abnormalities go as follow, 9qh+, gap(2)(q23), chtb(2)(q23), chtb(2)(p31), fra(2)(p23), 13ps+, Yq+, del(4)(q22-qter), chtb(4)(q31), gap(6)(q21), del(10)(p13-pter), del(10)(p15), gap(10)(q22)x2 Xp22.1-pter and q13.2-qter. Important numerical chromosome abnormalities we found are monosomies of chromosome 10, 13, 19, 22 ve Y.In another classification, we evaluated 639 metaphase plaques in 23 patients and we found 241 chromosome abnormalities of which 88% were structural and 12% were numerical abnormalities. In control group we studied 23 male individuals. For this group, we totally examined 1150 metaphase plaques and we found 182 (15.8%) chromosome abnormalities. We found statiscally significant increase in the ratio of chromosomal abnormalities in patients compared to controls (p<0.05).Key words: Sagliker syndrome, calcium, DNA, Sequence, cytogenetic