Early embryology; making a brain (Introduction)

by David Turell , Saturday, November 12, 2016, 19:33 (2933 days ago) @ David Turell

How to take stem cells and create the complexity of a brain with its different types of cells is now begun to yield to research:

https://www.sciencedaily.com/releases/2016/11/161111120737.htm

"It is mind-boggling to imagine how our brain develops from just a handful of cells at the early embryo into a highly convoluted biochemical and bioelectric system comprising more than 100 billion neurons in adults. Scientists at the Institute of Molecular Biotechnology (IMBA) in Vienna have published new research in EMBO Journal, in which they reveal how cells are instructed by a small RNA molecule to shape the complex layered structures of developing mouse brains.

"When stem cells divide to form new tissues and organs, they have to position their cell division apparatus in a specific orientation to position their daughter cells at sites where they experience different fate cues defining their subsequent function. The newly formed cells may then go on to take a specialised function -- in the brain, for example, they can become various types of neurons to generate and transmit electrical impulses -- or stay stem cells that will keep dividing to generate more cells. Failure to correctly induce fate decisions leads to multiple developmental brain disorders.

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"Fededa describes the approach: "By visualizing the spindle of the cells with a fluorescent marker in live cells, we observed that a family of six microRNAs called miR-34/449 influenced the spindle orientation during cell division. We then tested whether these micro-RNAs could also influence the orientation of mitotic spindles in developing mouse brains, using methodology established in Jürgen Knoblich's laboratory at IMBA. Indeed, we found that after deletion of miR-34/449 genes, mice developed smaller brains and these contained a larger proportion of stem cells called radial glial cells. This showed us that radial glial cells can grow relatively normally, but suggested that they are unable to further differentiate into more complex cells. We therefore concluded that miR-34/449 microRNAs must be required for normal brain development."

"The scientists at IMBA compared the gene expression patterns in cells with or without miR-34/449 and discovered a difference in the expression of a protein called JAM-A. This protein was interesting, as it was previously shown to have a role in orienting the mitotic spindle in other tissues. By engineering a JAM-A gene version that is insensitive to miR-34/449, the team at IMBA was able to pinpoint its relevance for mitotic spindle orientation. "Our findings show that in developing mouse brains, miR-34/449 regulates JAM-A to ensure the correct orientation of dividing cells and accurate formation of brain layers" concludes Daniel Gerlich. "The current research provides insights into the role of micro-RNAs in brain development, but similar mechanisms might be at place in other organs.'"

Comment: These are genomic proteins working automatically to achieve a proper organization of the brain. Imagine this throughout the embryo. Not by chance!