Lab Tour

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. 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.

 

“Gone FISH-ing”

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.  In the case of tetrasomy 18p, FISH can tell us whether the entire extra chromosome is made of material from the short arm of chromosome 18.

 

“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.  The DNA from people with 18q- and 18p- 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.

 

“For Posterity”

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:

Why don’t we get results?

At this time, we do not routinely provide written results of laboratory studies completed in our lab.  This is because we are a research laboratory.  As a research laboratory, our goals are very different from those of a clinical laboratory.  The goal of clinical labs is to provide diagnostic tests.  In contrast, the tests completed in our laboratory are not intended to provide information about a person’s diagnosis or prognosis.  Rather, the goal of the tests performed in our laboratory is to learn more about a chromosome change that has already been diagnosed.  In addition, research laboratories are not regulated by the agencies that oversee the protocols and quality control of clinical laboratories.  Therefore, we do not issue official reports regarding our findings.  We are working towards becoming a clinical laboratory, but this is a long process.  Of course, we will keep research participants updated about our progress in this area!

Some parents believe that the information gained from laboratory studies would change the treatment or prognosis of their child.  At this point in time, this is not the case.  Ultimately, we hope that this research will enable us to make predictions about a person’s health and development based on the precise location of the breakpoints.  Until that goal is reached, however, the information gained from the studies performed in our lab just give us more molecular details of the chromosome change that has already been identified.

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?

In most cases, the things we study within the laboratory are determined by the available funding.  At the present time, the laboratory is focusing primarily on 18p-, 18q-, and tetrasomy 18p.  However, we also request samples from individuals with other chromosome 18 changes.  There are two main reasons we do this.  First, we do not know where our research will take us in the future or what funding will be available.  We want to collect as many samples as possible in the hopes that we will someday have the resources to do additional studies.

The second reason we request samples from people that have a different chromosome 18 change is that, on occasion, unique chromosome changes may unexpectedly provide us with information about chromosome 18.  For example, two individuals with the same translocation may suggest that a certain part of chromosome 18 is susceptible to breaks and rearrangement.