Scientists at the University of Massachusetts Medical School have made an outstanding discovery that will pave to way to chromosome treatment for Down syndrome. Down syndrome is the most common genetic birth defect, affecting approximately one in about 800 babies, and is characterized by intellectual disabilities, unique facial features, visual and hearing impairments, and other health problems. Through their experimentation, these scientists led by Jeanne Lawrence have managed to "shut off" the extra chromosome responsible for trisomy 21, the genetic source of Down syndrome. Not only could this discovery lead to more effective treatments of the source of Down syndrome, but the same technology could be used to treat other genetic disorders.
How did they do it?
The answer comes from the sex-determining X chromosome. As you probably learned in basic biology, women have two X chromosomes and men have an X and a Y chromosome. For both sexes, the body only requires one to be activated. The body has a natural way of turning an extra X chromosome off in the form of an "off switch" gene called XIST that occurs on the X chromosome. The XIST gene produces genetic material called RNA that causes an X chromosome to deactivate.
Lawrence and her colleagues in in vitro experiments of Down syndrome cells took this XIST gene and tried to apply it to the extra chromosome in trisomy 21. They theorized that this XIST gene could deactivate the extra chromosome just like it deactivated the extra X chromosome. Tests of gene activity suggested that the extra chromosome had stopped functioning and in brain cells with the XIST gene, cells were able to grow more rapidly. Next research steps include trying to shut down the extra chromosome in a mouse with a version of Down syndrome. Hear Lawrence talk about the experiment in her own words:
What does this mean?
This discovery means that there is a strong basis from which to develop new treatments using this same concept of shutting down the extra chromosome in trisomy 21. For people currently living with Down syndrome, possible new treatments could help to alleviate intellectual and sensory impairments. Additionally, possible new prenatal treatments for Down syndrome fetuses derived from these findings could normalize brain development in the womb. This discovery also opens up new insight into the possibility of "chromosome treatment," where drugs and procedures can be designed to treat the genetic root of genetic disorders.
This is truly a huge victory for health science.