Alteration In Methylation Level At Differential Methylated Regions Of MEST And DLK1 In Fetus Of Preeclampsia

Background:Preeclampsia is a common pregnancy specific disease,that is characterized by development of hypertension and proteinuria after 20 weeks of gestation,sometimes progressing into dysfunction of multiple organs and is a major cause of maternal and fetal morbidity and mortality.The exact cause of Preeclampsia remains unknown.however,many theories indicate that abnormal placental development in early pregnancy triggers systemic inflammation,oxidative stress,and endothelial dysfunction,which lead to its clinical manifestations.Fetuses of preeclamptic women are exposed to in utero under-nutrition environment due to the poor blood supply to placenta.Depending on the severity of the insult during specific critical windows of fetal development,permanent tissue adjustments can occur,leading to long-term changes in organ function.the fetus has to adapt to a potentially unfavorable intrauterine environment and this adaption can lead to increased risk of chronic non-communicable diseases(NCDs)in later life.The children of preelamptic women had an increased risk of Hypertension,cardiovascular disease,metabolic diseases and cognitive dysfunction in adulthood.The underlying molecular mechanism remains unclear.Epigenetic processes are believed to play a pivotal role for the effect of environmental exposures in early life to modify disease risk throughout the lifespan.Persistent changes in imprinted genes induced by in utero conditions may be among the mechanisms contributing to the diseases in the later life.Imprinted genes are mediators regulating fetal and placental growth and development,and their expression and function are controlled by differentially methylated regulatory regions(DMRs)that carry parental allele-specific methylation profiles.DNA methylation is the most stable type of epigenetic modification modulating the transcriptional plasticity of mammalian genomes.DNA methylation changes induced by intrauterine exposures can modify gene expression and physiological function.Both MEST and DLK 1 are imprinted genes which have been reported to regulate adipocyte differentiation and then possibly involved in obesity,hypertension,and diabetes mellitus.Human MEST is an imprinted gene located at chromosome 7q32.2 that encodes a protein that belongs to a/β-hydrolase fold family.It is a paternally expressed gene that only transcribed from the paternal allele and functions as a candidate for a gene responsible for primordial growth retardation MEST has been suggested to be related to adipocyte differentiation and obesity.human DLK1 is an imprinted gene located at chromosome 14q32 frequently showing uniparental disomy(UPD)and is imprinted and expressed from the paternal allele.This gene encodes a transmembrane protein named pre-adipocyte factor-1(Pref-1)that contains multiple epidermal growth factor repeats that functions as a regulator of cell growth.Pref-1,an inhibitor of adipocyte differentiation and is considered a factor determining adiposity and associated with high risk of metabolic diseases in adulthood.Recently,increased serum Pref-1 was demonstrated in fetuses of preeclampsia-complicated pregnancy,and it may be a possible mediator leading to high risk of metabolic diseases in adulthood.Hypomethylation at MEST DMRs induced by GDM which is characterized by fetal macrosomia,was also observed.However,the effect of preeclampsia on the methylation level at fetal DMRs of MEST has not been described yet.We hypothesized that the methylation levels at fetal MEST and DLK1 DMRs may be different in preeclampsia and normal pregnancy.To verify our hypothesis,we analyzed the methylation levels at DMRs of MEST and DLK1 of umbilical cord blood of neonates born to preeclamptic and normal pregnancies.Objectives:The purposes of the current investigation were to clarify the changes in DNA methylation at MEST and DLK1 DMRs in fetus of preeclampsia and to explore the possible mechanisms behind the high risk of adult diseases in the offspring of preeclampsia.Methods:Fetal lymphocytes were isolated from umbilical cord blood of 78 women with preeclampsia and 95 women with normal pregnancy.Genomic DNA was extracted and then DNA methylation levels of MEST and DLK1 DMRs were determined by Mass ARRAY quantitative methylation analysis.Results:The methylation levels were detected in 20 Cp G sites of MEST DMR and 16 sites of DLKl DMR.Methylation changes were significantly different at CPG1,3,4,7.8,15,18.19,and 20 of MEST between preeclampsia and normal pregnancy(p=0.014,0.001,<0.001,<0.001,=0.001,=0.005,and =0.003,respectively).Significant differences were also observed at CPG 3 and 9 of DLK1(p=0.002 and 0.027,respectively).However,overall methylation at these DMRs were not affected.No significant differences were observed at any Cp G sites of MEST or DLK1 between mild and severe preeclampsia(p>0.05).Regression analysis revealed that DMR methylation levels were not associated with maternal age,birth weight,or Fetal gender.Conclusion:We conclude methylation changes at some Cp G sites of MEST and DLK DMRs in preeclamptic group.This may be among the mechanisms behind the high risk of adult diseases in the later life of offspring born to preeclamptic pregnancies.