Doctoral defence: Mario Reiman “Placental transcriptome in normal and complicated pregnancies”

On 21 January at 10.15 Mario Reiman will defend his doctoral thesis “Placental transcriptome in normal and complicated pregnancies” for obtaining the degree of Doctor of Gene Technology.

Supervisor:
professor Maris Laan, University of Tartu

Opponent:
Doctor Hannele Laivuori, Tampere University (Finland)

Abstract
This doctoral thesis focused on studying the placental transcriptome using the RNA-Seq method to understand pregnancy complications better. The study was the largest of its kind at the time, including placenta samples from all three trimesters of both normal pregnancies and those with various complications (including preeclampsia, gestational diabetes, low and high birth weight pregnancies). Several important discoveries were made during the work.

First, it became clear that RNA quality significantly impacts research results—even small differences in RNA integrity can lead to significant differences in gene expression measurements. This knowledge is critical for the design of future studies, as differences in RNA quality may obscure actual biological differences between study groups.

Second, placental gene expression profiles for preeclamptic pregnancies were distinctly different from normal, confirming the placental origin of the disease. Also, a significant overlap between the gene profiles of various pregnancy complications was noted. This was especially dominant for preeclampsia and low birth weight groups, suggesting a possible common mechanism of origin for these conditions.

In the study of recurrent pregnancy loss, extensive changes in the placental transcriptome, indicative of the miscarriage process, were observed. Gene analysis showed that the placental tissue was already on the path to cell death and pregnancy termination by the time the samples were taken, so the exact root cause of the termination could not be identified.

Finally, the parental origin of the genes was also investigated, and it was found that only a small part (12.1%) of the studied genes showed a clear parent-specific expression. These genes were either placenta-specific or expressed only in the adrenal gland in addition to the placenta. In addition, 14 genes were identified, of which 65–90% of RNA-seq reads originated from a single parental allele. The research results make an important contribution to understanding the molecular mechanisms of pregnancy complications and lay the foundation for further research in this field.