Down syndrome is the most common chromosome abnormality in humans, affecting 1 of every 691 babies in US every year. People with Down syndrome are often cognitively underdeveloped and have certain facial characteristics. The condition is dubbed “trisomy 21,” since it is caused by an extra set of chromosome 21 (the smallest human chromosome).
Recently, researchers at University of Washington have successfully corrected trisomy 21 in human stem cell lines. Detailed in this month’s edition of Cell Stem Cell, a team led by Dr. Li B. Li of the University of Washington delivered, through a viral vector, a foreign gene (TKNEO) into another gene (APP) on chromosome 21’s long arm. Cells then grown in conditions unfavorable for TKNEO activation were seen to spontaneously lose the chromosome with TKNEO. This technique, moreover, does not cause gene toxicity, a significant advantage in gene therapy.
With this new technique, the trisomy can be corrected in lab culture using stem cells derived from the patient’s own cells. The patient could then receive a transplant of his own stem cells without the trisomy, a potential therapy for blood-forming diseases associated with Down Syndrome. Furthermore, the ability to generate stem cells with and without trisomy 21 could lead to a better understanding of how Down Syndrome originates.