By Evan Bourtis staff writer
On Thursday Oct. 12 , University of Rochester genetics researcher Dr. Martha Susiarjo came to Fisher to talk about her research relating to how a group of genes, called imprinted genes, have an impact on fetal and placental development.
Her talk was part of the Loss Lecture series, an annual event where faculty members of the science departments pick a scientist to come to Fisher to speak about their work. Biology department chair Dr. Daryl Hurd and biology professor Dr. Edward Freeman helped to organize the event.
Hurd liked how Susiarjo was able to communicate complex genetics concepts to a college audience. “The mission of the Loss Lecture is we’re trying to educate college and sometimes high school students about science,” Hurd explained. “And it helps if there’s an issue of human health aspect to it and it helps when you have an excellent speaker who can relay very complex biological concepts to the college age audience.”
In the presentation, Susiarjo explained how she researched a group of unusual genes, called imprinted genes, which can affect maternal health. Hurd hopes that the lecture helped students appreciate how the research impacts human health.
“I hope that there’s some awe. Like, ‘wow, I didn’t realize that this is the level of understanding that we have about this complex problem,’ ” Hurd said. “…Something like miscarriages some number of years ago was a very mysterious thing. And now we’re starting to understand them and understanding the interplay between molecules and genes.”
In most cases, humans inherit two working copies of a gene, one from mother and one from father. The genes, in turn, provide instructions to construct proteins. However, for imprinted genes, only one of these gene pairs is expressed. This is because enzymes silence one of these genes in the pair by adding bulky methyl groups to the DNA strand, making the gene impossible to read.
This DNA modification to stop the gene from being expressed is called epigenetics, a natural process that occurs in healthy cells. Epigenetics is unusual because, even though the actual DNA sequence doesn’t change, the process produces heritable changes in how genes are expressed, by modifying the DNA strand.
As Susiarjo pointed out, silencing genes using epigenetics is an important process of human development in the fetus and placenta. If cells aren’t able to silence one of the imprinted genes by adding methyl groups, it could stop development or lead to serious diseases, like Prader-Willi Syndrome.
During her research, Susiarjo helped to uncover that the chemical Bisphenol A (BPA), which has been used to make plastics since the 1960s, may disrupt DNA methylation. Susiarjo explained that BPA, which can also disrupt the endocrine system, is a cause of concern for pregnant mothers, since it has been shown to seep into beverages and food through plastic bottles and plates.
Susiarjo and her research team discovered that when pregnant mice were exposed to BPA, they had high levels of the amino acid tryptophan in their blood. Susiarjo explained that, although tryptophan is important during pregnancy, elevated levels are associated with miscarriages.
Further research helped Susiarjo to develop a theory of why BPA increased miscarriages and tryptophan levels in mice, relating to the idea of epigenetics. Susiarjo discovered that, when the mice were exposed to BPA, the imprinted gene responsible for making a protein called IDO1 was not expressed. IDO1 protein is important for suppressing the mother’s immune system in the developing fetus during pregnancy. Without the protein, immune cells will see the fetus as a foreign object and attack it, leading to a miscarriage.
In healthy cells, only the maternal copy of the IDO1 gene is expressed. Susiarjo’s research helped to demonstrate that, when the mice were exposed to BPA, both copies of the gene were expressed, since the cells failed to add chemicals that would silence the paternal copy of the gene. Susiarjo also noted that IDO1 helps to metabolize tryptophan, so high levels of tryptophan in the blood may indicate a failure to produce IDO1.
Susiarjo is continuing her research into epigenetics. Her three published research papers can be accessed through the University of Rochester’s website and PubMed.