Every year, about 5,700 babies are born with Down syndrome in the United States, making it the most common chromosomal abnormality. The genetic condition is caused by an extra copy of chromosome 21, also called trisomy 21, resulting in developmental, physical, and cognitive differences, including everything from hearing loss and congenital heart defects to learning and speech difficulties. Japanese scientists from Mie University, however, may have discovered a gene editing technique that can eradicate that extra chromosome altogether.
Recently published in PNAS Nexus, the team’s findings outline how CRISPR/Cas9, a DNA-modifying technology, can snip away the surplus chromosome in affected cells. CRISPR relies upon enzymes to identify specific DNA sequences and, upon finding a match, it can eliminate entire DNA strands. For this study, the scientists carefully designed CRISPR guides to focus only on trisomy 21, a process known as allele-specific editing in which the “cutting” enzyme is specifically directed toward its desired target. Remarkably, the team discovered that, upon removing the extra copy with CRISPR, gene expression was normalized in their lab-grown cells.
Follow-up tests revealed that genes tied to nervous system development became more active and that those linked to metabolism slowed down after the editing. Corrected cells also grew faster and had a shorter doubling time when compared to untreated cells.
Aside from these lab-grown cells, the scientists also tested their CRISPR guides on skin fibroblasts, which were sampled from people with Down syndrome. Here, the editing technique worked yet again, successfully removing the additional chromosome in several cases. Even so, CRISPR can interact with healthy cells as well, emphasizing that these early insights are far from being implemented on a clinical scale. In response, the team is currently working on refining their methodology so that only trisomy cells are targeted by their gene editing.
To explore the full study, visit PNAS Nexus.
A team of Japanese scientists from Mie University have developed a gene editing technique that targets the extra chromosome responsible for Down syndrome.
Sources: Trisomic rescue via allele-specific multiple chromosome cleavage using CRISPR-Cas9 in trisomy 21 cells; CRISPR used to remove extra chromosomes in Down syndrome and restore cell function; CDC: Down Syndrome; CDC: Living with Down Syndrome
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