Dr. Mobley from the University of California, San Diego’s Down Syndrome Center for Research and Treatment and Dr. Jamie Edgin from the University of Arizona’s Down Syndrome Research Group spoke at our webinar on January 29, 2015. Thank you, Dr. Mobley and Dr. Edgin – and all the people who attended the webinar. To listen to a copy, please click here.
What is the number of copies of APP with typical Trisomy 21?
The answer is 3. This is due to the presence of an extra copy of the entire 21st chromosome, which harbors the gene for APP and as many as 500 other genes.
Would inhibiting DYRK1A be beneficial?
Quite possibly. What is not clear at present is exactly what changes in the Ds brain are due to the extra copy of the gene for this protein. What we do know is that it is an enzyme that acts on a number of neuronal functions and that an increase in the amount of this protein is likely to cause changes that impact normal function. A number of labs are working on this problem, including ours [UC San Diego Down Syndrome Center for Research and Treatment], and more data should be coming forward in the next few years. An ongoing trial of a non-specific inhibitor of this protein may provide important insights into what might be accomplished by creating treatments that would reduce its levels or effects.
What ages could benefit from the therapies that were discussed?
A good question. Our studies and others focused on increased inhibition might well lead to treatments that would be given to children.
Our studies on APP target age-related changes in neurons and logically would be administered to adults. But since the problems that an increased number of the APP gene causes are already detected in young people, we envision that such treatments may ultimately also be given to children.
The vaccine that targets a product of APP that I discussed will be first be administered to adults but then might well used in young adults and possibly children.
Can you tell us more about endosomal enlargement – timing, APP dose-dependence and tests?
Endosomal enlargement is indeed present in the very young brain and is a direct consequence of increased levels of APP. It is almost certainly seen in all people who have the full Trisomy 21. The test for this would therefore be the test which shows whether or not someone is a full or partial trisomy. More sophisticated tests aimed at defining the number of APP genes present in the genome would also be useful, but I would suggest that the simply karyotype test should suffice for almost everyone with Down syndrome.