Influence of gestational age on placental epigenetic profile

Author(s)

Sarah Blima Paulino Leite

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2012-09-18

Examining board members

Ester Silveira Ramos; Alessandra Cristina Marcolin; Maria Terezinha Serrão Peraçoli

• Advisor: Ester Silveira Ramos

Abstract

Genomic imprinting, an epigenetically regulated process by which genes are expressed accordingly to their parental origin, is involved in placental growth and development. In 11p15.5 region, there are many genes regulated by two Imprinting Control Regions (ICR1 and ICR2), in which are found two Differentially Methylated Regions, H19DMR and KvDMR1, respectively. Imprinting patterns seem to be adjusted during placenta development. In humans, there is little information on genomic imprinting and placental development, especially for early stages of development due to technical difficulties in obtaining these placentas. The description of mosaicism in methylation pattern restricted to placenta or between placenta and fetus shows a unique epigenetic profile of this organ. The 5-hidroxymethylation, which has no role in gene silencing, can be confused with DNA methylation in molecular analysis. The main aim of our study was to verify the influence of gestational age (GA) in DNA methylation profile of ICRs 1 and 2 in chorionic villi, as well as the existence of intra-placental methylation profile mosaicism. The presence of hydroximethylation in the KvDMR1 was also investigated. Samples were collected from placentas, 25 from chorionic villi (CV) (15 of the 3rd gestational trimester and 10 of the 1st trimester) and nine from umbilical cord (UC) in 1st trimester (paired with the CV samples). Four 3rd trimester placentas were separately analyzed for mosaicism. DNA methylation profile was verified by Methylation Specific PCR (MS-PCR), and Combined Bisulfite Restriction Analysis (COBRA) and Methylation-Sensitive Enzyme Digestion Method associated with Real-Time PCR (DESM-RT), in addition to hydroximethylation test in the KvDMR1 region. With qualitative assays (MS-PCR and COBRA), it was observed a monoallelic methylation pattern, and, only for the H19DMR, differently methylated CpGs were observed. For the H19DMR, we observed methylation means of 0.43 in CV and 0.31 in UC of 1st trimester, and 0.41 in CV of 3rd trimester. For KvDMR1, we observed means of 0.47 in CV and 0.57 in UC of 1st trimester, and 0.41 in CV of 3rd trimester. No hydroximethylation in the KvDMR1 was observed. There were no significant differences between the means of different GAs or between tissues by F and t tests for both regions. No positive correlation was found on methylation profile for H19DMR and KvDMR1 between tissues. In relation to mosaicism, there were no significant differences in methylation profile between different cotyledons sampled in the same placenta. The results showed a discrepancy between embryonic (UC) and extra-embryonic (CV) tissues. Although it was not observed significant changes in methylation profiles of H19DMR and KvDMR1 in different GAs, the presented results are important to research on dynamics of genomic imprinting phenomenon during pregnancy, studies of intra-placental mosaicism and placenta epigenetic profile in relation to other tissues. (AU)

• FAPESP's process: 10/03519-9 - Influence of gestational age on placental epigenetic profile
• Grantee: Sarah Blima Paulino Leite
• Support Opportunities: Scholarships in Brazil - Master