One of the great mysteries of life is the process by which organisms begin as one cell and develop into creatures composed of many. Think about it — a human, who started as a single cell, is made up of trillions in adulthood.
Early in development, stem cells seem to hold some innate program that directs them to mature into different parts of the anatomy — skin cells, neurons, cells for the liver, kidneys, heart, and lungs. How does this fantastic process happen?
Claude Desplan and Nathalie Nériec are trying to understand this fundamental activity in a familiar but tiny creature — the fruit fly, or Drosophila melanogaster. In a recent review paper, Desplan and Nériec provide an overview of the state of the field that is unraveling the procedure by which neural stem cells develop into the neurons that form the fly visual system. Desplan is Silver professor of biology at NYU and affiliate faculty at NYU Abu Dhabi and, after graduating, Nériec is a now postdoctoral associate at NYUAD.
Flies are fit for study because though their anatomy is relatively simple, their visual system is complex. The full fly brain contains approximately 150,000 neurons, with the optic lobe neurons, which process visual information, making up nearly 60 percent of the total.
We are trying to figure out how much of the program is already encoded within the stem cell, and how much depends on where and when the neurons are generated in the brain during development.
Researchers are also trying to understand how a single stem cell can form different types of neurons. "How is the program established in an organism that specifies different types of neurons?" Nériec asked. "We are trying to figure out how much of the program is already encoded within the stem cell, and how much depends on where and when the neurons are generated in the brain during development."
Understanding this process of development from stem cell to neuron may improve therapies by allowing scientists to produce cells that are as similar as possible to natural cells.
Understanding this process of development from stem cell to neuron may improve our understanding of brain diseases like Alzheimer's and Parkinson's. "A goal of therapies for neurodegenerative diseases would be to know the type of whatever neurons are dying, make them again, and put them back in the patient," Nériec said.
Though these kinds of therapies are a long way off, understanding the fundamentals of the development of neural diversity is essential. And the more researchers learn about how neurons are made in nature, the better chance they have of developing therapies to treat these diseases.