Epigenetic dynamics during capacitation of naïve human pluripotent stem cells

Early human development and stem cell-based human embryo models

The use of stem cells to model the early human embryo promises to transform our understanding of developmental biology and human reproduction. In this review, we present our current knowledge of the first 2 weeks of human embryo development. We first focus on the distinct cell lineages of the embryo and the derivation of stem cell lines. We then discuss the intercellular crosstalk that guides early embryo development and how this crosstalk is recapitulated in vitro to generate stem cell-based embryo models. We highlight advances in this fast-developing field, discuss current limitations, and provide a vision for the future.

Mini-heterochromatin domains constrain the cis-regulatory impact of SVA transposons in human brain development and disease

SVA (SINE (short interspersed nuclear element)-VNTR (variable number of tandem repeats)-Alu) retrotransposons remain active in humans and contribute to individual genetic variation. Polymorphic SVA alleles harbor gene regulatory potential and can cause genetic disease. However, how SVA insertions are controlled and functionally impact human disease is unknown. Here we dissect the epigenetic regulation and influence of SVAs in cellular models of X-linked dystonia parkinsonism (XDP), a neurodegenerative disorder caused by an SVA insertion at the TAF1 locus. We demonstrate that the KRAB zinc finger protein ZNF91 establishes H3K9me3 and DNA methylation over SVAs, including polymorphic alleles, in human neural progenitor cells. The resulting mini-heterochromatin domains attenuate the cis-regulatory impact of SVAs. This is critical for XDP pathology; removal of local heterochromatin severely aggravates the XDP molecular phenotype, resulting in increased TAF1 intron retention and reduced expression. Our results provide unique mechanistic insights into how human polymorphic transposon insertions are recognized and how their regulatory impact is constrained by an innate epigenetic defense system.

5-azacytidine inhibits Sox2 promoter methylation during the induction of Thy-1+Lin- cells into hepatocytes

OBJECTIVE

To investigate the changes and functions of Sox2 gene expression and promoter methylation during induced differentiation of bone marrow mesenchymal stem cells (BMSCs) into hepatocytes (HCs).

METHODS

Rat bone marrow Thy-1+Lin- cells were prepared and divided into control group (directed induction of differentiation into HCs) and experimental group (5-azacytidine intervention induced differentiation). The mRNA expression levels of ALB and Sox2 were detected by fluorescence quantitative polymerase chain reaction (PCR), and the Sox2 gene promoter methylation level was determined by Bisulfite sequencing PCR (BSP).

RESULTS

Sox mRNA expression level was significantly increased in experimental group compared to the control group at 0, 7, and 14 days, respectively (all P<0.05). The Sox2 promoter methylation level was gradually increased after 0, 7 and 14 days induction in both groups, accompanied by an increase in methylated loci (all P<0.05). Statistical significance was present in CpG methylated loci between groups (all P<0.05).

CONCLUSIONS

The expression of Sox2 gene increased first and then decreased in the process of inducing rat BMSCs into stem cells, and the methylation level of CpG loci in the promoter region changed dynamically, with an increased overall methylation level. After 5-aza treatment, the Sox2 promoter was in a non-methylated state, and its mRNA expression increased, which hindered the cell differentiation.