Stanford Medicine-led researchers found what did Stanford researchers discover about the human brain being two separate organs: the front and back of the brain arise from different progenitor cells and function as two ancient nervous systems. Published in Nature Neuroscience on Sept. 18, the study says the adult brain’s forebrain, midbrain and hindbrain do not all trace back to one early cell.
Kyle Loh, the senior author and an associate professor of developmental biology, said, "We’ve shown for the first time that the front of the brain arises from a totally different progenitor cell than the back of the brain." He added, "Our discovery means that we can now grow neurons from the back of the brain, the hindbrain, in a petri dish and study their functions."
Carolyn Dundes and Rayyan Jokhai
Carolyn Dundes and Rayyan Jokhai, the co-first authors, found during gastrulation that the hindbrain follows a separate developmental path running in parallel to the pathway that creates the forebrain and midbrain. That result puts the back of the brain on a different track from the regions tied to higher-level thinking such as language, consciousness and abstract reasoning.
The hindbrain sits at the back of the skull and is often called the brain stem. It controls breathing, sleeping, heartbeat and hunger urges, and its neurons also control the muscles of the face, tongue and throat that affect speech and swallowing. Scientists had struggled for decades to generate human hindbrain neurons in the laboratory.
SMA and ALS
The practical value is in the diseases tied to those neurons. The discovery could help research into SMA and ALS, including work on hindbrain neurons that has been hard to model for decades.
SMA is a leading genetic cause of death in children under 1 year of age. ALS is often diagnosed between the ages of 40 and 70. With the study now published, researchers can use the new developmental model to study how the hindbrain forms and to grow those cells in a petri dish for disease research.
The study also directly challenges the older view that a single progenitor cell early in development gives rise to the entire brain. The new model says the front of the brain comes from a different progenitor cell than the back, a split that fits the idea of two ancient nervous systems that evolved independently over hundreds of millions of years.
