A game of cellular whodunit, ODYSSEY Gulf Blog (year 3), Day 52, July 14, 2012
Day 52, Sunday, July 14, 2012
Dear Family and Friends,
Within a cell the DNA is maintained in structures called chromosomes. These are a combination of DNA and protein that ultimately package the DNA so that when a cell divides into two, each daughter cell gets exactly 1 set of the set of DNA instructions.
My career has been dedicated to studying the impact of pollutants like chromium, depleted uranium, nanoparticles, nickel and other chemicals on chromosomes and the DNA within them. It is a passion I discovered and an approach I learned under my mentor, Steve Patierno, who shares the same passion (Thanks Steve!). While working with Steve, and following my years with him, my major focus was understanding how these chemicals turn normal cells into tumor cells by altering chromosome structure and number, damaging DNA and altering the cellular mechanisms that regulate and protect these structures. We are still extensively involved in this work and have extended it into pioneering the study of how pollutants damage chromosomes and DNA in marine species.
Each species has a specific set number of chromosomes. Humans have 46 chromosomes. 22 matched pairs, 11 that come from mom and 11 that come from dad. Plus 1 pair of sex chromosomes known as the X and Y chromosomes. Females are XX gaining one X from each parent. Males are XY getting an X from mom and a Y from dad. Sperm whales have 42 chromosomes, 20 matched pairs plus the two sex chromosomes. The particular number of chromosomes is not unique to one species as for example other whales have 42 chromosomes, but the specific number is unique to a species as sperm whales always have 46. This number is tightly regulated and maintained. Alterations in this number can have dramatic consequences. Down’s syndrome is a consequence of a one extra chromosome (number 21). Lung cancers often have more than 60 chromosomes.
You can harvest and prepare cells so that you can see their chromosomes. Roughly speaking, in these preparations – the chromosomes look kind of like an “X” or if the arms are closed an “I”. You can chemically treat the chromosomes in the laboratory to reveal a pattern of dark and light bands that is specific to each pair of chromosomes. The patterns are not defined as simply as 1 dark followed by, 2 light followed by 1 dark or anything like that. There are too many. Instead, they are described in more abstract terms. For example, chromosome 18, when banded, looks like a gummi bear. In our lab, it is known more as the Wallace chromosome given Captain Bob’s legendary passion for eating gummi bears. The X chromosome is known as the “girl in a bikini” because the most prominent dark bands are placed where one might imagine a bikini. The nicknames continue for each pair and really help teach chromosome recognition. Sandy excels at this analysis.
The pairs of banded chromosomes can be organized on a piece of paper or computer screen into a template called a karyotype that roughly organizes them from largest to smallest. The karyotype is unique to each species. I have attached a picture of a human karyotype that Sandy made. This one is male with an X and Y chromosome. Can you see the Wallace gummi bear chromosome (#18) and the girl in the bikini chromosome (X)? Johnny and I are working to define a variety of whale karyotypes including one for sperm whales. We have not yet devised clever names for their chromosomes as we are still learning them.
Damage to the structure of the chromosomes, which shows up as an alterations in the banding pattern, can have as dramatic consequences as alterations in chromosome numbers.
Our society has decided that the impact of damaging chromosomes is so significant that testing for a chemical’s ability to damage them is a standard test for evaluating the safety of new drugs and determining health risk. Both the US Food and Drug Administration (FDA) and the US Environmental Protection Agency (EPA) include chromosome damage testing as a required test in their protocols. If a pharmaceutical company develops a new drug and it damages chromosomes, it will not be approved by the FDA for use. When a company is developing a drug and it breaks chromosomes, they stop its development and move on to another. The only exception is the rare instance when the disease is so lethal the risk of chromosome damage is the lesser of two evils.
We are applying these same tests to the Gulf whales. We are finding the chromosomes in some whales are affected. This outcome is another answer to that repeated question – What are you finding?
We have grown cell lines from each whale and assessed the status of their chromosomes. The analysis reveals different groups of whales. Some whales appear to be normal. Others appear to have their chromosomes affected. It is a major concern as aberrant chromosomes can lead to many long term negative outcomes. We believe we have ruled out possible experimental artifacts. Thus, it suggests something out here is affecting the whales on a fundamental level.
For us in the Wise Lab, it now becomes a game of cellular whodunit as we attempt to piece together the factors that may explain what is causing this effect. It might be the metals. It might be the oil. It might be the dispersants. It might be some combination of them. We shall find out. I don’t think its global warming. But, regardless of why, the outcome is not good.
It was a slow day at sea today. The kind of day that lulls you into a quiet state. No whales on the array. No dolphins on the bow. Just the general routine of a team ascending and descending the mast looking for whales in a vast ocean space.
We did see one, maybe two. That made for some excitement as it was a beaked whale, maybe two. But, alas it was too far off and while we found it twice (or two different whales once each), we could not get close enough to sample it nor could we stay with it any further. We also saw a small sea turtle in the Sargasso weed. We did collect some samples as this team did its first Sargasso weed collection of the leg (Picture attached).
So a couple of perks to a day filled with the rhythm of a steady routine.
I’ll end tonight with the sunset (picture attached)
P.S. If you want to see our location on Google Maps we are at:
just paste in the coordinates and click search
If you want to read the previous days of these messages- they are
posted at www.usm.maine.edu/toxicology/gulf and click on “read logs
John Pierce Wise, Sr., Ph.D.