Browsing by Author "Laukkanen, Ida"

Epigenetics is the study of changes in gene expression without alterations in the DNA sequence. Epigenetic modifications, of which DNA methylation (DNAm) is the most known, are crucial for many biological events, especially for normal development and genomic imprinting. In imprinted genes, only one of the parental alleles is consistently monoallelically expressed. The epigenome can be altered by various environmental factors such as diet and chemicals. Moreover, evidence indicates that assisted reproductive technology (ART) is associated with distinct DNAm patterns. Still, it is unclear whether these alterations are a consequence of ART procedures themselves or the underlying subfertility. This thesis aimed to study whether ART procedures and subfertility are associated with aberrant DNAm at the imprinted DLK1-DIO3 locus in the human placenta. The genes encoded from this paternally imprinted locus are essential in mammals' fetal and placental development. Moreover, recent evidence suggests that downregulation of the DLK1 gene is associated with ART and subfertility. Therefore, two gene regions, the IG-DMR and the DLK1 promoter, were chosen as study objects. The IG-DMR acts as the main regulator of gene expression at the whole DLK1-DIO3 locus, and promoter regions are considered important regulators of the expression of their corresponding genes. Eight ART, four subfertility, and six control samples of human placental DNA were studied. The subfertility group consisted of couples who were committed to initiating fertility treatments but eventually got pregnant spontaneously. The study was performed using traditional bisulfite sequencing, after which the differences in DNAm levels between study groups were statistically analyzed. As expected, significantly decreased DNAm level was observed in the placentas of subfertile couples compared to controls. Surprisingly, no significant differences were addressed between ART and control groups in either region. The partly unexpected results are explained by the fact that aberrant methylation at distinct imprinted DMRs, including the IG-DMR, is caused by the in vitro culture media. Moreover, the results indicate that the regulation of DLK1 expression is more complicated than that solely by the IG-DMR and the DLK1 promoter. Further research should be dedicated to differentiating the impacts of ART and subfertility on the epigenome and phenotype to better understand the health implications of ART.