Washington: Scientists have discovered that proteins in fluids bathing the brain are essential for building it.
The finding promises to advance research related to neurological disease, cancer and stem cells.
Before now, the fluid surrounding the brain was generally considered to be a sort of salt-solution that simply maintained the brain`s ionic balance.
Recent reports of fluctuating proteins in the fluid suggested otherwise, however. And thus, a multi-institutional research teams at the Children`s Hospital in Boston, led by Maria Lehtinen, Mauro Zappaterra and Christopher Walsh and researchers from the George Washington University School of Medicine and Health Sciences in Washington, D.C., decided to take a closer look at what proteins in the fluid do.
They found that when embryos and their brains are growing, a type of protein that tells brain cells to multiply increases in the so-called cerebrospinal fluid.
"This study is a game changer," said Anthony LaMantia, director of the GW Institute for Neuroscience at the GW School of Medicine and Health Sciences and an author on the paper, along with Thomas Maynard, Associate Professor of Pharmacology and Physiology at GW.
"It`s remarkable that signals are coming from the cerebrospinal fluid – it makes sense but no one really thought about it in this way."
Brain cells in the cortex -- the part of the brain responsible for cognition, learning and memory -- multiply and move to their appropriate position between the second and third trimester of embryonic development in humans. But until now, researchers have had little luck finding the molecular signals that direct the process as well as determining how the signals get delivered to the cells that need them.
The current team extracted cerebrospinal fluid from mouse embryos around two weeks after conception, when their brains develop most quickly. The fluid contained high levels of a protein, insulin-like growth factor or Igf2, which is known to help stem cells multiply and differentiate. Notably, the protein isn`t elevated after birth.
When the authors blocked Igf2, stem cells in the brain stopped making brain cells, which resulted in abnormally tiny mice brains. And when the team placed brain stem cells in a dish filled with Igf2-rich, embryonic cerebrospinal fluid, the cells proliferated rapidly.
"This was clearly the environment the stem cells needed to be happy," LaMantia explains.
The study has been published in the journal Neuron.