Do ESCs produce a large array of proteins?

[TytoAlba95]

'Analyses of global histone modification patterns in ESCs have previously suggested that the ESC genome is subject to generalized histone acetylation and lysine 4 H3 methylation (H3K4me). As these are both transcription-activating modifications, these changes in global genomic architecture and global histone modifications suggest that the chromatin environment in ESCs is highly euchromatic, and the genome is therefore highly permissive for gene expression. This would account for the pluripotent nature of ESCs, with the genome becoming more structured, condensed, and heterochromatic during differentiation, leading to loss of pluripotency. '

Does this mean that the ESCs make all types of hormones and enzymes that are encoded by different cells?

 

[Ygggdrasil]

No. At very early stages, embryonic stem cells are not transcribing their genomes; instead, they rely on mRNAs provided by the mother to allow translation of many of the protein needed during the early stages of embronic development. The maternal-to-zygotic transition (in which transcription is activated from the zygotic genome and the embryo begins to rely on its own transcripts rather than transcripts provided by the mother) is associated with changes in chromatin accessibility and cells beginning upon the path of differentiation (e.g. going from totipotent cells to pleuripotent cells).

While these later stage ESCs do generally have more "open" chromatin, transcriptional regulation still occurs. An important feature of these cells are regions of "bivalent chromatin," which contains both chromatin marks associated with active transcription (e.g. H3K4me3) as well as chromatin marks associated with repression (e.g. H3K27me3). These bivalent regions are likely one way in which the early embryo can repress transcription of cell-type specific genes while still keeping them poised for activation later in development.

A good, technical review of the many changes to chromatin state that occur during embryonic development can be found here: https://science.sciencemag.org/content/361/6409/1332

 

[TytoAlba95]

Thank you so much