November 2014 Uncategorized

Guiding Growth: from Genes to Mentorship

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Biology Professor Tamara Davis

In Tamara Davis’s lab, students like Ekaterina (Katia) Vlasova ’15 and the teacher collaborate on cutting-edge research. Exploring the biology of inheritance, they are working to understand one of the big questions of genetic research: Are parents’ genetic contributions to their child’s development equal?

“The answer to this is yes,” Davis said. “And no.” In her KIM Talk about her lab’s research, the Bryn Mawr biology professor took on the “no” part of that answer.

She explained: “We know that children get two copies of their genes, one from mom and one from dad. And, for the most part, the two copies are both expressed, or ‘turned on,’ in cells. But for a small group of genes, only one copy, from one parent, gets expressed.”

Those are called imprinted genes—imprinted because they “remember” which parent they came from—and they comprise a very small percentage of our genes. Only about 100 out of our 25,000 or so genes fall into this category.

“For about 50 percent of them, it’s the maternally inherited copy that’s working—making a protein product, building cells, building organs. The dad’s copy is silent,” Davis said. “Conversely for about another 50 genes or so, it’s the dad’s copy that is producing product.”

“Why does this matter?” Davis asked.

While the work of her lab is contributing to a larger understanding of our genetic inheritance, the payoff isn’t just academic, she explained. Anomalies in imprinted genes can manifest as developmental and neurological disorders. Davis cited two human disorders, Prader-Willi syndrome and Angelman syndrome, that arise from abnormalities in the expression of those genes.

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Ekaterina Vlasova ’15

Working with undergraduate researchers such as Vlasova—50 at last count over her years at Bryn Mawr—Davis has been exploring just how the cell tells which copy belongs to the mother and which to the father and how it knows which copy to express. What is it about the DNA in the parents’ chromosomes that allows them to be expressed differently?

The answer to that question lies in the overall structure of the chromosome. DNA has to be condensed to fit inside our cells. Davis explained: “It’s this condensation, the compaction of the DNA into the shape of a chromosome, that’s critical for understanding whether a gene is being expressed or not.”

Take, for example, a maternally expressed gene, pumping out RNA and protein products. That gene will be in a loose compaction where the silent dad’s copy will be compacted. “So we’re studying the differential levels of compaction on mom’s copies of these genes versus dad’s copy,” Davis said.

Two types of molecules—histones and methyl groups—influence how compacted the DNA is at a particular gene. In the past couple of years, as Davis and her research team began looking closely at one particular imprinted gene, they discovered something new. In this case, they found that the methyl groups, which are typically located symmetrically across from each other on a strand of DNA, were asymmetrical.

Davis’s lab team is the first to have observed this phenomenon—the study was published in May 2014—and is continuing its investigation. Vlasova and Megan Guntrum ’16 are currently exploring the biochemical reason for this asymmetry and whether it is characteristic of imprinted genes or unique to this one particular gene.

But more than groundbreaking research flourishes in Davis’s epigenetics lab, as Vlasova testified in her KIM Talk. “I’ve learned the most from actively engaging with the scientific process and applying theory to practice,” she said. “It’s through my ongoing mentorship with Dr. Davis that I’ve flourished most, both as a student and as a scientist.”

Over the past three years, Davis has mentored Vlasova, first as a faculty advisor and now as a major and research advisor. “I’ve been amazed at my mentor’s patience and understanding,” she continued, “when it came time to addressing the mistakes I had made—and, trust me, I’ve made a few. Her patience and her words of guidance helped me learn from those errors and tremendously aided my growth.”

Nor is Davis an anomaly at Bryn Mawr. Pointing out that the College has four times the national average of female students majoring in the STEM fields, Vlasova said, “Just maybe it is because we have such fantastic role models to look up to: strong, confident, and driven women working in their fields to engage with the topics they feel really passionate about.”

Curious to hear more? Listen to the KIM Talks.