EPIGENETIC CHANGES DURING HUMAN THYROID CELL DIFFERENTIATION.

Journal: 2020/April - Thyroid

ISSN: 1557-9077

DOI: 10.1089/thy.2019.0772

Abstract:

It has been demonstrated that the transcription factors TAZ, PAX8 and NKX2-1 are co-expressed in the nucleus of thyroid cells. Furthermore, TAZ is known to enhance the transcriptional activity of PAX8 and NKX2-1 as well as the key thyroid specific gene, thyroglobulin (TG), suggesting a critical role for TAZ in the control of thyroid cell speciation. We previously reported that the small molecule ethacridine, identified as a TAZ activator, was able to induce thyroid specific transcription in endodermal cells differentiated from human embryonic stem (hES) cells using activin A. Since transcription factors are epigenetically regulated in cell differentiation, we investigated the epigenetic changes in the promoter regions of these key transcription factors during in vitro differentiation of hES cells into thyrocytes.We initially profiled chromatin accessibility using the technique of ATAC-seq and then examined DNA methylation and histone acetylation in the promoter regions of the 3 selected thyroid transcription factors and the thyroid specific genes during hES cell differentiation.ATAC-seq analysis showed enriched chromatin accessibility of TAZ, NKX2-1 and PAX8 after exposure to activin A and ethacridine. There were no methylation changes found in the NKX2-1, PAX8 and TAZ promoters by bisulfite sequencing. In contrast, acetylation of histone H4 (AcH4), and, specifically, acetylation of lysine 16 (H4K16ac) was observed in each of the promoters when measured by immunoprecipitation (ChIP) PCR assays which correlated with the activity and expression of NKX2-1 and PAX8 as well as NIS, TSHR and TG genes Conclusion: These results indicate that ethacridine treatment of activin A derived endodermal hES cells leads to enhanced chromatin accessibility which, in turn, allows histone H4 acetylation in the regulation of active genes for speciation of thyroid follicular cells from hES cells. Key words: Epigenetic modification; TAZ, NKX2-1, PAX8, thyroid; human embryonic stem cells; acetyl histone H4; acetylation of histone H4 at lysine 16; ATAC-seq.

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