brain plasticity: how neurons grow dendrites (Introduction)

by David Turell , Wednesday, April 27, 2016, 19:21 (3133 days ago) @ David Turell

In order for the brain to have plasticity new neurons must grow dendrite connections and create networks of connectivity. The genes and molecules driving this process have been found:-http://medicalxpress.com/news/2016-04-biologists-brain-cells-message-network.html-"Biologists at the University of Iowa have determined a group of genes associated with neurons help regulate dendrites' growth. But there's a catch: These genes, called gamma-protocadherins, must be an exact match for each neuron for the cells to correctly grow dendrites.-***-"Gamma-protocadherins are called "adhesion molecules" because they stick out from a cell's membrane to bind and hold cells together. The researchers learned about their role by giving a developing brain cell in a mouse the same gamma-protocadherin as in surrounding cells. When they did, the cells grew longer, more complex dendrites. But when the researchers outfitted a mouse neuron with a different gamma-protocadherin than the cells around it, dendritic growth was stunted.-***-"Gamma-protocadherins act like molecular Velcro, binding neurons together and instructing them to grow their dendrites. Weiner and his team figured out their role when they observed paltry dendritic growth in mouse brain cells where the gamma-protocadherins had been silenced.-"The researchers went further in the new study. Using mice, they expressed the same type of gamma-protocadherin (labeled either as A1 or C3) in neurons in the cerebral cortex, a region of the brain that processes language and information. After five weeks, the neurons had sizeable dendritic networks, indicative of a healthy, normally functioning brain. Likewise, when they turned on a gamma-protocadherin gene in a neuron different from the gamma-protocadherin gene with the cells surrounding it, the mice had limited dendrite growth after the same time period.-"That's important because human neurons carry up to six gamma-protocadherins, meaning there are many combinations potentially in play. Yet, it seems the "grow your dendrite" signal only happens when neurons carrying the the same gamma-protocadherin gene pair up.-"The neurons actually care who they match with," says Weiner, associate professor in the Department of Biology, part of the College of Liberal Arts and Sciences. "It takes what we knew from biochemical studies in a dish and shows that protocadherins really mediate these matching interactions in the developing brain."-"The team reports that star-looking cells called astrocytes also play a role in neurons' dendrite development. Astrocytes are glial (Greek for "glue") cells that help to bridge the gap between neurons and speed signals along. When the molecular binding between an astrocyte and neurons is an exact match, the neurons grow fully formed dendrites, the researchers report.-"'Our data indicate that g-Pcdhs (gamma-protocadherins) act locally to promote dendrite arborization via homophilic matching and confirm that connectivity in vivo depends on molecular interactions between neurons and between neurons and astrocytes," the authors write."-Comment: Again we see the controls and the complexity of these processes. Not by chance.