How the FISH Technique Could Quickly Find Genetic Mutations

By Tony Wang


Chemotherapy and radiation therapy are both treatments that are often used to treat cancer; however, they are also known to cause several harsh side effects in patients. These side effects can not only harm patients, but, more worryingly, may also impact their future children. This is supported by empirically-gathered data that shows that radiation and chemotherapy treatments are “genotoxic,” which means that they can not only mutate a human’s DNA, but can also damage the chromosomes in a patients’ healthy, noncancerous cells. When this occurs in a germline cell—which are egg cells and sperm cells in women and men, respectively—it can lead to very serious fetal and birth defects in their future children.

cell lines
Image Credit: Flickr @ Andy Leppard

Currently, there are no efficient, effective, and affordable tests that can be used to track a man’s germline cell health in regards to whether or not they contain any chromosomal mutations caused by chemotherapy and/or therapy treatments. This is particularly concerning, as if a man is unaware of his germline cell health, and attempts to conceive a child, they may unknowingly pass on a defect to them. But recent evidence from a study led by Andrew Wyrobek at the Lawrence Livermore National Laboratory suggests that this may soon change. According to Wyrobek, a new test that can quickly and easily identify when a sperm cell is carrying chromosomal mutations could soon be released to the public. In a paper published in the journal PLOS One, the international team reported their success in adapting an established cellular DNA analysis technique called fluorescence in situ hybridization (FISH) to probe sperm DNA. This version of the FISH technique, known as the AM8 sperm FISH protocol, has been in the works by the research team for several decades. This method can detect balanced chromosomal abnormalities, which are genetic rearrangements with no loss or gain of genetic material. These balanced rearrangements are compatible with live birth and heritable to future pregnancies, and affected children are likely to experience reduced fertility when they want to have children of their own.

The research team evaluated the AM8 FISH approach on sperm from nine Hodgkin lymphoma patients, who provided samples before, during, and after a multidrug treatment regimen and radiation therapy. Results from the FISH protocol tests were astonishingly accurate, indicating that sperm produced during the Hodgkin lymphoma treatment had ten times more chromosomal defects compared with sperm produced prior to treatment.

However, according to Wyrobek, the sperm FISH method is still in an early research phase and it will require additional validation and commercial development before it becomes available in doctor’s offices. But although the FISH method is still not ready for commercial use yet, it does bring lots of hope for the field of chemotherapy and radiation treatments. If found to be successful, it could help prevent many tragic births, not only saving lives, but also preventing much grief.

Citations:

No changes were made to the following image, https://flic.kr/p/p6YGQ, License: Creative Commons Legal Code

No changes were made to the following image, https://flic.kr/p/9z8dWi, License: Public domain

https://genetics.thetech.org/about-genetics/mutations-and-disease

https://scitechdaily.com/how-to-quickly-and-easily-find-mutated-sperm-just-go-fish/

https://www.genome.gov/genetics-glossary/Fluorescence-In-Situ-Hybridization#

https://www.mayoclinic.org/tests-procedures/chemotherapy/about/pac-20385033


What Did You Learn?

Questions:

1. Why do radiation and chemotherapy treatments cause mutations?


Mutations are almost always caused by damaged or altered DNA, which is the genetic material in living things. Radiation and chemotherapy treatments treat cancer by damaging the cancer DNA in order to keep it from dividing uncontrollably. However, the radiation and chemotherapy also affect the regular healthy cells, which is why these treatments are often very risky.


2. How does the FISH technique work?


Fluorescence in situ hybridization (FISH) is a laboratory technique for detecting and locating a specific DNA sequence on a chromosome. The technique relies on exposing chromosomes to a small DNA sequence called a probe that has a fluorescent molecule attached to it. The probe sequence binds to its corresponding sequence on the chromosome. The FISH technique is very cheap, effective, and easy to use, which is one of the reasons it is becoming more widely used in modern medicine.


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