Summary: A recent study has uncovered how two morphogens, WNT and Sonic Hedgehog, function as key regulators in early human brain development. Researchers utilized custom devices and stem cell-derived organoids to discover that just five days of exposure to these signals triggers gene programs that influence the formation of brain regions.
Interestingly, sensitivity to these morphogens differed among donors and even within cell lines from the same individual, indicating both genetic and epigenetic factors at play. These insights shed light on the dynamic nature of early brain development and how individual variations can arise at a molecular level.
Key Facts:
- Signal-Driven Development: WNT and Sonic Hedgehog morphogens are crucial in modulating gene activity that shapes brain structure within days.
- Personal Variation: Sensitivity to morphogens shows differences across individuals and among stem cell lines from the same donor.
- Genetic and Epigenetic Impact: Variability arises from both genetic factors and changes occurring after conception.
Source: Yale
Just a few weeks post-conception, stem cells begin shaping the human brain’s structure.
A new study led by Yale demonstrates that during early development, these morphogens act as signaling agents, activating gene programs that direct stem cells towards becoming more specialized brain cells.
The Yale team discovered that sensitivity to these morphogens varies not only between distinct donors but also among stem cells derived from the same individual.
“This study marks a significant advancement in our understanding of human development, influenced by both genomic variations among individuals and epigenetic modifications within each person,” stated Flora Vaccarino, co-senior author of the study published in the journal Cell Stem Cell on May 1.
Led by Vaccarino and Andre Levchenko, another co-senior author, the research involved a unique device called Duo-MAPs, which helped expose human stem cell-derived organoids to the two essential morphogens typical in brain development.
The WNT morphogen functions along one axis of the developing central nervous system, while the Sonic Hedgehog morphogen operates along a different axis.
Over a short five-day period, the positioning and concentrations of these morphogens influenced gene activity dictating the structure and cellular makeup of nearly all brain regions.
Notably, the analysis indicated distinct differences in gene activity linked to the morphogens across different individuals and stem cell lines.
Some organoids demonstrated greater sensitivity to the WNT morphogen, with activated genes predominantly focused near the brain’s lower regions where the hindbrain forms, while others showed reduced sensitivity, directing activity towards upper brain areas like the cortex.
Similarly, stem cells more responsive to Sonic Hedgehog exhibited heightened gene activity in the developing basal ganglia, whereas those with lower sensitivity had more significant responses in the cerebellum.
The variability in morphogen response genes among donors mostly related to immune functions. Surprisingly, even within cell lines from a single individual, gene activity related to metabolism shifted between experiments.
The differences observed among donors likely arise from their genetic backgrounds, while variations in the same donor’s stem cell lines are attributed to epigenetic changes or mutations that occurred post-conception.
These findings emphasize the fluidity of brain development, not just between individuals but even within the same person.
“It was noteworthy to find that human brain development can be sparked by a brief exposure to these significant signals, demonstrating a strong robustness to variations in gene expression,” Levchenko remarked.
This research paves the way for enhanced modeling and understanding of critical developmental processes that can be connected to specific human subjects more accurately than previously possible.
Co-lead authors of the study included Yale’s Soraya Scuderi and Alexandre Jourdon, along with Taeyun Kang from Levchenko’s team. Members from the Systems Biology Institute, the Yale Stem Cell Center, and the Department of Neuroscience also contributed to the research.
Funding: This research was primarily supported by the National Institutes of Health, backed by an innovator award from the Yale Kavli Institute for Neuroscience.
