According to a study in Neuron by researchers at Columbia's Zuckerman Institute, part of the answer lies in how slowly our brain cells mature—a process governed by a uniquely human gene duplication.
Unusually Slow Cell Maturation
Scientists focused on microglia, the brain's immune cells. Beyond defending against pathogens, microglia organize developing brain circuits by deciding which synaptic connections neurons keep or eliminate.
The study revealed a stark species difference in microglial development:
- Mouse Microglia: Reach full maturity in about 3 weeks.
- Human Microglia: Take 4 to 8 years to fully mature.
This extended developmental timetable (neoteny) allows microglia to gradually fine-tune complex neural networks over many years.
The Role of SRGAP2
This delayed maturation is driven by human-specific copies of a duplicated gene called SRGAP2, which were found to be nearly 10 times more active in microglia than in neurons.
The gene acts as a biological brake, slowing down microglial development so it stays synchronized with the gradual maturation of human neurons. Together, this coordinated delay enables the brain to build denser, stronger neural connections.
Why It Matters
Because microglia are increasingly linked to neurodevelopmental disorders and neurodegenerative conditions, understanding their uniquely long developmental timeline could help researchers better treat brain diseases in the future.
Source: Science Daily
