The H19 Gene Imprinting in Normal Pregnancy and Pre-eclampsia

Objectives: To characterize the H19 gene imprinting in the placental tissues of normal pregnancy and pre-eclampsia. Methods: A total of 188 subjects at 5-9 weeks, 54 at 10-12 weeks, 50 at the second trimester, 65 at term of gestation, and 30 with pre-eclampsia at the third trimester were recruited. Their DNA and RNA were extracted from the placental tissues. The H19 genotypes for individuals were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and the H19 gene imprinting was identified by reverse transcription-PCR (RT-PCR) and the Rsal-based RFLR The levels of H19 RNA transcripts in the pre-eclampsia patients with the H19 heterozygote were measured by quantitative RT-PCR. The frequency of the H19 heterozygote, the H19 imprinting status among different trimesters of pregnancy and the clinical symptoms in the pre-eclampsia patients were analyzed. Results: (1) About 40-46% of subjects at varying stages of normal pregnancy showed the H 19 heterozygote, and 24 out of 87 (27.59%) heterozygous cases were at 5-9 weeks of gestation, but no single one in other stages displayed biallelic expression of the H19 gene. (2) Thirteen out of 30 pre-eclampsia patients were H19 heterozygous and six of these showed the biallelic expression of the H19 gene (loss of imprinting). (3) The pre-eclampsia patients with the biallelic expression of H19 tended to have severer hypertension although their H19 RNA transcription level was similar to that in those with monoallelic expression. Conclusions: (1) The biallelic expression of the H19 gene exists in some cases at the early stage of normal pregnancy and changes into monoallelic expression near 10 weeks of gestation. The dynamic alternations in the patterns of the H19 gene imprinting may regulate the maintenance of normal pregnancy. (2) The loss of the H19 gene imprinting in the placental tissues of pre-eclampsia patients may be associated with severe hypertension, contributing to the pathogenic process of pre-eclampsia. (C) 2009 Elsevier Ltd. All rights reserved.