Down’s syndrome could soon be treated in the womb by targeting a key gene, scientists say. Researchers have found a way to alter the extra chromosome in a baby’s cells which causes the condition.
People with Down’s suffer a learning disability which varies for each person caused by a one-off genetic change in the sperm or egg.
A healthy baby is born with 46 chromosomes but babies with Down’s have an extra copy of chromosome 21 which changes how a baby develops.
The crucial chromosome 21 is called gene OLIG2. In a brain model grown in a lab using cells extracted from Down’s patients, researchers found that using drugs to inhibit OLIG2 stopped the production of harmful neurons. When a Down’s brain was triggered in mice using the same technique it found these neurons were being overproduced by the cells and were linked to impaired memory.
Assistant Prof Peng Jiang, of Rutgers University in the US, said: “Down’s syndrome is a common neurodevelopmental disorder, and cognitive defects in Down’s syndrome patients may arise from imbalances in excitatory and inhibitory neurotransmission.
“Understanding the mechanisms underlying such imbalances may provide opportunities for therapeutic intervention. “Our results suggest the OLIG2 gene is potentially an excellent prenatal therapeutic target to reverse abnormal embryonic brain development, as well as improving postnatal cognitive function.”
All pregnant women are offered screening tests for Down’s and the risk increases with the mother’s age. The NHS said a woman who’s 20 has about a one in 1,500 chance of having a baby with Down’s, while a woman who’s 40 has a one in 100 chance.
The crucial chromosome 21 is called gene OLIG2 (Image: Getty) As well as suffering delayed development some children may have more complex needs such as being autistic or having attention deficit hyperactivity disorder (ADHD).
Heart conditions, hearing and vision problems, thyroid conditions and infections, such as pneumonia, are also more common in Down’s people. The new treatment promises to reverse abnormal embryonic brain development and improve memory after birth. The study used stem cells collected from Down’s patients that can turn into other cells in the brain.
They genetically reprogrammed those cells to human-induced pluripotent stem cells (hiPSCs). These special cells can develop into many different types of cells, including brain cells, during early life and growth. Bu using brain cells derived from stem cells with an extra copy of chromosome 21, the scientists grew a 3D brain organoid model in the lab, which resembles the early developing human brain. They also did the same with a mouse brain in a live mouse.
They found that inhibitory neurons – which make your brain function smoothly – were overproduced in both models, and adult mice had impaired memory. They also found that the OLIG2 gene plays a critical role in those effects and that inhibiting it led to improvements.
The combination of the brain organoid and mouse brain model could be used to study other neurodevelopmental disorders such as autism spectrum disorder. It may also help scientists better understand the mechanisms in Alzheimer’s disease. Down’s patients often develop early-onset Alzheimer’s disease, Prof Jiang noted. The study was published in the journal Cell Stem Cell.