Small cultures of human neuronal cells developing in a dish are not quite “brains in a petri dish” as they are sometimes described. But these cerebral organoids give scientists unprecedented options for studying and understanding the early embryonic stages of human brain development. Two recent papers published in Nature show just how powerful these neuroscience research tools are. The first paper characterizes these neural developments more fully, while the second uses organoids as a tool to show how a neurodevelopmental disorder known as Timothy Syndrome develops.Making a brain-like thingThe first paper focused on fully understanding brain organoids, which start out as a cluster of neural stem cells. The authors of the paper describe them as cell systems that build themselves up with their own internal growth program.
After a month of growth in the dish, these organoids started to show brain regionalization, with different clusters of cells appearing to differentiate into the forebrain, midbrain, hindbrain, and retina, according to the gene markers for each of these regions.After six months of growth, brain organoids developed 10 distinct cell classes, each of which mapped to neuron populations in the developing human brain, like astrocytes, retina cells, and cortex cells. Different brain organoids showed different distributions of these 10 neuron cell populations, and these differences were linked to the growth environment that the organoids were in. So, even though the brain organoids weren’t receiving growth signals from a human body, the culture environment could still direct their growth.