One of the major goals of the Chromosome 18 Clinical Research Center is to link the genes on chromosome 18 to specific medical or developmental concerns. This is important because it will allow us to predict how a deletion or duplication will affect an individual. We will be able to make individualized health and screening recommendations based on a breakpoint. We will also be able to talk about the issues that they are
not at risk to have. Eventually, we hope that these genes and the proteins they code for will be targets for treatments.
There are several different ways to establish the link between genes and features of a chromosome deletion. One way to do this is to compare the chromosome changes in people with the same physical finding. For example, we have looked at everyone in our study with 18q- who has been diagnosed with growth hormone deficiency. We have compared their deletions and found the area of the chromosome that they are all missing. We therefore know that the gene that causes growth hormone deficiency falls in that region. Although we still haven't identified the "growth hormone deficiency gene", knowledge of the critical region is still helpful. We know that people who are missing this part of the chromosome have a high likelihood of having growth hormone deficiency. This also tells us that people who are not missing the growth hormone deficiency critical region are very unlikely to have growth hormone deficiency.
Defining critical regions is possible because we have enrolled many individuals with different sized deletions of different regions of the chromosome. Critical regions have been established for several features of both 18p- and 18q-, such as mood disorders, kidney abnormalities, and hearing loss. Recently, the Chromosome 18 Registry & Research Society's website has been updated to include information about these regions. We encourage families to visit these pages and learn more about critical regions.
At this time, we don't have as much information about critical regions for duplications of parts of chromosome 18. However, as time goes on, and we are able to enroll more individuals with small duplications we will learn how duplications of chromosome 18 affect health and development. This is truly a community effort made possible because so many families have enrolled in the research.
