Variations in the 16p11.2 region of the genome are associated with autism spectrum disorder. While people with genetic deletions in this region have larger heads (macrocephaly) and people with genetic duplications have smaller heads (microcephaly), both variation types affect brain development and function.

The brain organoids were created using induced pluripotent stem cells derived from people who have 16p11.2 genomic variations—three people with deletions, three with duplications and three non-variant controls. Researchers obtained a skin sample from each person, gave the skin cells a molecular cocktail that converted them to stem cells, then treated the stem cells in a way that coaxed them into becoming brain cells, preserving each patient's unique genetic background.

The organoids revealed that RhoA—a protein that plays a big part in many basic cellular functions, such as development and movement—is more active in both 16p11.2-deleted and 16p11.2-duplicated organoids than it is in organoids without these variations. Over-active RhoA led to a slowdown in neuronal migration, the process by which brain cells get to where they need to be for normal fetal development and function in adulthood.

Organoids aren't perfect reproductions of the brain. They lack connections to other organ systems, such as blood vessels, and so don't encapsulate full human biology. In addition, therapeutics tested on brain organoids are added directly. They don't need to get across the blood-brain barrier, specialized blood vessels that keep the brain largely free of microbes and toxins.

Regards

John
EditorialAssistant
Immunogenetics Open Access