Do you like neuroscience? Here are soem basics about our brain cells.
The bulk of our neurons are created before we are born and dont regenerate as we go through life. There is an area of the brain called the “hippocampal dentate gyrus” which is largely responsible for memory actually continue to produce new neurons throughout your entire lifetime. All these new cells are based on neural stem cells (NSCs), and are vital for the maintenance of our cognitive capacities as we grow older. It was only recently that scientists could figure how to these neural stem cells turn into regular, fully functioning neurons.
At the heart of the mystery is the fact that these stem cells arent predestined to become neurons, but can instead develop into other types of brain cells such as astrocytes and oligodendrocytes. Both of these are examples of glial cells, which surround neurons and help to protect and support them. However, in the hippocampus, all NSCs do go on to become neurons, and none produce oligodendrocytes.
Glial cells are the most abundant cell types in the central nervous system. Types of glial cells include oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells and they maintain homeostasis, form myelin, and provide support and protection for neurons in the central and peripheral nervous systems.
Until now, it had been largely accepted that stem cells do not control their own future, and are instead stimulated to develop a particular type of cell by specific compounds in their external environment. However, a new report in a journal caleld “Cell Stem Cell” reveals that NSCs (neuron stem cells) in the hippocampus are in fact masters of their own destiny, and contain internal mechanisms that steer their development in favor of becoming neurons rather than glial cells.
Oligodendrocytes are one type of glial cells that surround neurons and support them in their functioning. The authors of the study bred speicifc mice to lack an enzyme called Drosha in their hippocampal stem cells. [Drosha is a Class 2 ribonuclease III enzyme that in human beings is encoded by the DROSHA (formerly RNASEN) gene.] From this process, they found that this caused them to produce oligodendrocytes rather than neurons. The function of Drosha is to eliminate sections of micro RNA that control the activity of the transcription factor nuclear factor IB (NFIB), which in turn regulates the expression of certain genes that determine what type of cell an NSC becomes. Nuclear factor 1 B-type is a protein that in humans is encoded by the NFIB gene.
This led the researchers to suspect that NFIB (nuclear factor IB) must play a major role in driving the development of NSCs into glial cells instead of neurons, and that Drosha prevents this from occurring by inhibiting NFIB. To confirm this, the team then bred mice that lacked NFIB, and found that this restored the ability of their NSCs to develop into neurons rather than oligodendrocytes.
The creation of new neurons from NSCs or neurogenesis is vital for the maintenance of cognitive function, and age-related disruptions to this process have been associated with the onset of dementia. Understanding how neurogenesis works could therefore prove to be the first step in the development of new treatments for a range of cognitive disorders.