Maintaining the blood-brain barrier during development

Beginning in the earliest stages of development, a layer of cells known as the blood-brain barrier encapsulates the brain, protecting it from bacterial infection and viruses. As the brain expands rapidly during development, the blood-brain barrier must expand at the same rate to maintain its protective qualities.

Whitehead Institute scientists led by Member Terry Orr-Weaver have determined exactly how the blood-brain barrier is maintained during rapid growth—the result of a unique communication signal between the expanding brain and the glial cells that make up the blood-brain barrier.

By examining these processes in larval fruit flies (which are frequently used as models for human development), researchers discovered that the expanding brain instructs subperineurial glia cells to enlarge by creating multiple copies of their genomes in a process known as polyploidization.

Their discovery offers new insights into how tissues communicate with each other and—for the Orr-Weaver lab—has led to an exciting new avenue of research.

Blood Brain Barrier Polyploidization

The process of polyploidization is vital to maintaining the blood-brain barrier during expansion. Here, researchers test the barrier using a dye (the dye is white above). When glial cells undergo polyploidization, the barrier is maintained, and dye does not penetrate the barrier (left image). When polyploidization is inhibited, the barrier is broken, and the dye penetrates the barrier (right image). Credit: Genes & Development

“It has really opened up a whole new area to look at, so we can understand the mechanistic basis by which this communication happens,” says Orr-Weaver. “Does it happen at the organ level, or does it happen locally? There’s really a lot to sort out.”

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