A Transcriptomic Study of Maternal Thyroid Adaptation to Pregnancy in Rats

Thyroid disorders are relatively frequently observed in pregnant women. However, the impact of pregnancy on maternal thyroid has not been systematically evaluated. In the present study, using the rat as an animal model, we observed that the weight of maternal thyroid increased by about 18% in late pregnancy. To gain an insight into the molecular mechanisms, we took advantage of RNA-seq approaches to investigate global gene expression changes in the maternal thyroid. We identified a total of 615 differentially expressed genes, most of which (558 genes or 90.7%) were up-regulated in late pregnancy compared to the non-pregnant control. Gene ontology analysis showed that genes involved in cell cycle and metabolism were significantly enriched among up-regulated genes. Unexpectedly, pathway analysis revealed that expression levels for key components of the thyroid hormone synthesis pathway were not significantly altered. In addition, by examining of the promoter regions of up-regulated genes, we identified MAZ (MYC-associated zinc finger protein) and TFCP2 (transcription factor CP2) as two causal transcription factors. Our study contributes to an increase in the knowledge on the maternal thyroid adaptation to pregnancy.