When families enroll in the Chromosome 18 Clinical Research Center, we ask for a blood sample from the patient and, if possible, his or her parents. We request five tubes of blood: four green and one yellow top tube. Many families have completed the blood draw; shipped the samples to Texas; and wondered, “What are they going to do with our blood, anyway?”
Patty Heard and Erika Carter work in the Research Center’s laboratory. Once they receive the blood in the laboratory, they get right to work.
The blood from individuals with 18q- or tetrasomy 18p undergo FISH (Fluorescence In Situ Hybridization) analysis. Erika uses the blood in the tubes with the green tops. In addition to some “food’ for the blood cells, she also adds a material called a “mitogen” to the mixture. This mitogen stimulates the white blood cells to divide and reproduce, providing Erika with more cells with which to work. Three days later, Erika puts some cells onto a slide and examines them using FISH. This technique involves colored “probes” that stick to the ends of the chromosome and tell us whether or not the tip of the chromosome is present. It can also tell us whether there is an extra or missing piece of the end of another chromosome.
“DNA Isolation and Microarray”
While Erika is studying the chromosomes under a microscope, Patty is busy using the blood from the yellow-top tubes. She uses a specialized kit to extract DNA from the blood cells. Eventually, all patient samples we receive will undergo microarray analysis. Microarray analysis is a new technology that the laboratory has recently started to use. This technology allows us to define the breakpoints of the deletion more precisely. This is an important step in identifying the genes that are responsible for different features of this condition. Microarray analysis also enables us to look at other parts of the genome to see if there are any other chromosome changes that had not been previously reported.
Of course, it is impossible for us to predict where science will take us in the years to come. We can never predict when we might need to re-analyze or run a new test on a sample. We therefore create “cell lines” from all of the blood samples we receive, regardless of the type of chromosome change present. A cell line is a group of cells that can continue to divide and reproduce indefinitely. In order to create the cell lines, Patty “transforms” the original cells by infecting them with a special type of virus. Once the cells are growing nicely, she freezes them in liquid nitrogen and stores them until we need to use them again. This assures us that we have an unlimited supply of a person’s DNA, and that we will not have to request another blood sample from a family.
Frequently Asked Questions about the Laboratory:
Will we receive results from the analyses completed using our blood samples?
In the past, we have been unable to release results of our molecular genetic lab tests. The main challenge to releasing these particular results has been the fact that we are not a CLIA-approved lab. That simply means that our genetics lab is a research lab. This is different from a clinical lab, which typically performs more routine medical tests then generates a report to be included in your medical records. We have been working to find a way to be able to let you know what are our findings are despite our status as a research lab. We are happy to report that we have been successful! We are starting to send out the participant 's genetic data to the families. We have started with the first enrollees in the study and are working through every study participant that has submitted a blood sample.
Why do you ask for samples from the parents?
While we, as researchers, are most interested in a sample from the person with a chromosome change, parental samples can also play an important role in the research. For example, on microarray analysis, there may be a result that is difficult for us to interpret without knowing whether a parent has the same result. We also use the parental samples to determine whether the chromosome change occurred on the chromosome inherited from the mother or the chromosome inherited from the father. However, we do not routinely test the parents to determine whether they have the same chromosome change as their child.
Our family has a chromosome change other than 18p-, 18q-, and tetrasomy 18p. What do you do with our samples?
The priorities of the laboratory are determined by the available funding. At the present time, the laboratory is focusing primarily on 18p-, 18q-, tetrasomy 18p, and ring 18. We also request samples from individuals with other chromosome 18 changes. These samples can also provide valuable information about chromosome 18. However, as the lab priorities are determined by funding availability, these samples will likely be analyzed after samples from individuals with one of the above conditions.