Magic embryology: epigenetic controls (Introduction)

by David Turell , Tuesday, August 04, 2020, 21:37 (1572 days ago) @ David Turell

A new study of these controls:

https://www.sciencedaily.com/releases/2020/08/200804111532.htm

"A research team at the Max Planck Institute for Molecular Genetics in Berlin has explored the role of factors in embryonic development that do not alter the sequence of DNA, but only epigenetically modify its "packaging." In the scientific journal Nature, they describe how regulatory mechanisms contribute to the formation of different tissues and organs in early mouse embryos.

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"Epigenetic regulator factors are part of this molecular mechanism and act to modify the "packaging" of the DNA molecule without altering the underlying genetic information. Specifically, they act to bookmark the DNA and control what parts can be accessed in each cell.

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"'The same regulator is present in all cells, but can have very different tasks, depending on cell type and time of development," says Stefanie Grosswendt, one of the first authors of a new study in the scientific journal Nature.

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"An eight-day-old mouse embryo looks a bit like a seahorse and does not have any organs yet. "From the outer appearance of an early embryo, one can often only guess which structures and organs will form and which will not," say bioinformatician Helene Kretzmer and biologist Zachary Smith, who are also both first authors of the publication. "Our sequencing allows for a much more precise and high resolution view."

"The single-cell analysis gave them a highly detailed view over the first nine days of mouse development. Often, switching off a single regulator led to ripple effects throughout the network of interacting genes, with many differentially activated or inactivated genes over the course of development.

"Removing the epigenetic regulator Polycomb (PRC2) had a particularly striking impact. "Without PRC2, the embryo looks egg-shaped and very small after eight and a half days, which is very unusual," says Kretzmer. "We see vast changes to how DNA is packaged that happens much earlier, long before the embryo develops morphological abnormalities."

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"The researchers found that PRC2 is responsible for limiting the amount of germline progenitor cells -- the cells that later become sperm and eggs. Without PRC2, the embryo develops an excessive number of these cells, loses its shape, and dies after a short time.

Comment: Obviously, since many tissues are so different in form and functions, there have to be regulators to active that portion of DNA that for each specific cell type. This degree of complexity has to be designed. Not by chance.