The work reveals that the front and back sections of the brain are established by separate progenitor populations separated by an impassable molecular boundary long before they ever begin communicating.
Stanford Researchers Overturn Decades of Brain Biology
Mapping the Otx2 and Gbx2 Progenitor Populations
For generations, biologists operated under the standard model that every cell in the brain originated from a single ancestor cell that divided and differentiated across all brain regions. Stanford investigators examining mouse embryos during gastrulation found that two separate groups of progenitor cells express different genes from the earliest stages of formation.
Cells marked by the Otx2 gene give rise exclusively to the forebrain and midbrain, while cells marked by Gbx2 are destined for the hindbrain. According to the study, these two populations never overlap, swap roles, or generate each other’s cell types. Chromatin packaging analysis confirms that the DNA within these progenitor cells exhibits fundamental structural differences from the very beginning, restricting each group to its own developmental pathway.
Rayyan Jokhai, a graduate student and co-first author of the research, notes that past attempts to generate hindbrain neurons in laboratory settings likely failed because protocols tried to induce forebrain and midbrain progenitors into becoming hindbrain cells.
Tracing an Evolutionary History Spanning Millions of Years
The dual-origin model is not unique to mice. The Stanford team traced developmental data across 550 million years of evolutionary history, identifying the same dual-origin pattern in chickens, zebrafish, and acorn worms. Even in jellyfish—which diverged from our evolutionary branch roughly 600 to 700 million years ago—distinct nervous systems form at opposite ends of the organism independently.
While combining them into one organ may be more efficient, the brain retains this ancient arrangement of two separate components.
New Pathways for Treating ALS and SMA
This structural clarification immediately impacts the study of neurodegenerative disorders that selectively target the hindbrain, such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). SMA stands as a leading genetic cause of death in infants under the age of one, while ALS is most commonly diagnosed in adults aged 40 to 70. Both conditions progressively destroy motor neurons in the hindbrain, impairing vital functions like swallowing and breathing.
Historically, studying these disorders in vitro required growing functional hindbrain neurons, a process hampered by starting with incorrect progenitor cells. Utilizing the newly identified progenitor identity, the Stanford team successfully induced human pluripotent stem cells to form functional hindbrain motor neurons in the laboratory. These cultured cells generate action potentials and express specific proteins corresponding to regions of the hindbrain that control the face, tongue, and throat.
Researchers indicate that establishing the correct cellular starting point also opens new avenues for studying neural circuits housed within the hindbrain, including those responsible for regulating hunger responses targeted by medications such as semaglutide.
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