|Statement from University of Missouri on NCL/CCL Test|
Recently, the TTCA became aware of problems with some of the NCL DNA testing. On July 8, 2010, the University of Missouri posted a notice for owners of Tibetan Terriers tested for NCL on http://www.caninegeneticdiseases.net/CL_site/mainCL.htm.
This notice explains that the University is confident that the mutation for NCL is correct, however there was a technical problem reading some of the cheek-swab samples, and that some of the carrier and affected results might have initially been misclassified. This led to the redesign of the DNA test, and a retesting of cheek swab samples that had originally tested as carrier or affected.
Unfortunately, even after this redesign, it became clear that there was still a problem. Reporting of the retests was supposed to be put on hold due the problem. However, some results from the retesting mistakenly appeared on the OFA site. These results were later removed from the website.
In the meantime, the TTCA has asked OFA to remove all NCL results from the website until the problems are resolved and retesting is complete and the results verified. As of Monday, July 19, 2010, all results have been removed. We have also been in contact with the University of Missouri and we are hopeful that this situation will be resolved quickly and correctly.
Below you will find a statement from Liz Hansen, University of Missouri, which explains this issue. Both OFA and the University of Missouri have been very responsive. Please be patient while this problem is resolved.
Brenda J. Brown
|Dear Tibetan Terrier owner,
We would like to update you on the status of the DNA test for NCL. As we acknowledged last month, a problem with the design of our test became apparent when we began testing primarily with samples collected by cheek swab. We redesigned the test, and believed we could begin reporting revised results last week. However, we then found that there were some exceptions, or “impossible” results with the new test (a normal parent producing an affected offspring, affected parent with normal offspring, or elderly dogs testing affected but still alive, which are all impossible). On Friday, we identified a rare, neutral mutation site nearby the location of the mutation that causes NCL. This second mutation has no relationship to the disease, but a mutation at this second site caused the redesigned test to read incorrectly in the few dogs where it is present. Another redesign of the test is being evaluated now, and when we are confident that it will produce correct results without fail, we will again retest all the samples that have given carrier or affected results previously.
We want to make clear that the mutation causing NCL is not in question. The problem has been with the design of the test that allows the mutation site to be evaluated. Unfortunately, our first 2 designs of the test resulted in appearance of rare, but not unheard of, problems that can happen with DNA testing. Real life DNA research and testing is not as fast or clear-cut as it appears on TV shows. Our efforts are focused on resolving this and getting all concerned TT owners accurate test results. We ask your patience as we work through this. We understand that you all want results as soon as possible, and we will get them to you – but we want them to be correct, more than we want them to be speedy.
We apologize for any distress or concern this situation has caused. Please rest assured that we will report results just as soon as we can be certain that they are reliable and correct.
Liz Hansen, on behalf of the staff at AMGL & Dr Gary Johnson
Animal Molecular Genetics Laboratory
University of Missouri – College of Veterinary Medicine
321 Connaway Hall
Columbia, MO 65211