HMN 2025: How Fresh insights into the inner workings of the developing brain could lead to autism treatments

While there is a vast amount of information about the human brain and how it develops and works, much of the organ is still uncharted territory. But new research published in the journal Nature is giving us new insights into a type of brain cell called the GABAergic interneuron and its role in the developing brain. These findings could help explain how conditions like autism and brain disorders in children develop.

GABAergic interneurons are a vital part of the brain. They release the neurotransmitter gamma-aminobutyric acid (GABA), which regulates brain activity by switching neurons on and off. Disruptions in their functions can lead to a number of disorders, including epilepsy, schizophrenia and autism.

Creating a ‘mini-brain’ in the lab

Now, scientists from the Weill Institute for Neurosciences at the University of California, San Francisco, have discovered how these neurons multiply in the developing brain, a process that was not previously well understood.

Because this process may only occur in humans, the research team could not use animal models. So they used stem cells to create a “mini-brain,” a 3D structure that mimics a part of the fetal brain from which many cortical interneurons arise. This structure appears around the eighth week of pregnancy and disappears at about eight months.

The researchers found that microglia, the brain’s specialized immune cells, can trigger a dramatic increase in the number of GABAergic interneurons in the developing brain. They do this by releasing a protein called insulin-like growth factor 1 (IGF1) that signals early-stage brain cells to create more of these vital neurons. When the team turned off IGF1 signaling, the interneurons stopped multiplying. However, there was no change when they deleted this gene in a mouse model, suggesting the process may be unique to humans.

“Our findings reveal a previously unappreciated role of microglia-derived IGF1 in promoting the proliferation of neural progenitors and the development of GABAergic neurons in the human brain,” wrote the researchers.

Although the study is a significant step forward in understanding the inner workings of the developing brain, it has some limitations. The stem-cell-derived mini-brains, for example, cannot fully replicate the sheer complexity of the body’s master organ. Nevertheless, further research on microglia and IGF1 should reveal even more about what is happening inside the developing brain. And since problems with GABAergic neurons are linked to various neurodevelopmental conditions, this new knowledge could one day lead to effective treatments for epilepsy and autism.

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