Expression of the syncytin-1 and syncytin-2 genes in the trophoblastic tissue of the early pregnancy losses with normal and abnormal karyotypes.

Abstract

Syncytin-1 and syncytin-2 which are endogenous retroviral genes products play a great role in syncytialization during trophoblast differentiation in normal placental tissues. In aneuploidic placentas due to the low level of pregnancy-induced hormones an alteration was occurred in the syncytialization process, while in the presence of cytogenetically abnormal karyotype the effect of syncytin gene expression levels on syncytialization process and in occured to spontaneous abortions is not clear. To reveal this, we investigated in syncytin-1 and syncytin-2 genes expression levels of chromosomally abnormal and normal trophophoblastic tissues and we also discussed the effect of the syncytin gene expression levels to the occurense of the spontaneous abortion. To each one of the trophoblastic cells; cultivation, harvesting, banding, and analysis were performed and the chromosomes were classified according to the presence of abnormality and normal XY constitution. To exclude the maternal decidual cell contamination, female karyotyped abortion materials were omitted in control group. The patient group consisted of thirty six placental tissues including trisomy 16 (n=10), triploidy (n=9), monosomyX(n=9), trisomy 21 (n=5) and trisomy 7 (n=3). The control group was consisting twenty placental tissues with XY karyotypes. The some part of the dissected frozen trophoblastic cells were used for RNA isolation and were proceeded to the determination of the expression levels of syncytin-1 and syncytin-2 genes by single-step Real Time PCR. The cDNAs were obtained by probes used in the same PCR stages. The sequence analysis of the syncytin-1 and syncytin-2 genes were performed, and read by the usage of the FinchTV 1.4.0 program. Between the expression levels of syncytin-1 and syncytin-2 genes were statistically difference in the patients and controls. There was a difference (p<0.0001) between trisomy 7 and other patient groups and controls, regarding to the expression of syncytin-1 gene. Numerous mutations in the syncytin-1 and syncytin-2 genes (on the expression sites) were detected, and the mutation rate was higher in the syncytin-1 gene compared to the syncytin-2 gene in the patient and in the control groups (p<0.001). The results of the study indicate that the expression of the syncytin-2 genes could be altered in the presence of chromosomally abnormal trophoblastic tissues, and these could lead to the loss of pregnancy due to the insufficient syncytialization. In sum, the current research has value for the further studies covering the mechanisms of trophoblast cell fusion, and syncytiotrophoblast regeneration, and thus the pathophysiology of human placental development in the presence of genomic anomaly.