Associate Professor, McAuley Scholar
Biology and Biomedical Sciences
Heather Axen graduated from Cornell College in 2006 with a B.A. in biochemistry and molecular biology and continued on to complete her Ph.D. from the University of Vermont in 2011. After completing postdoctoral fellowships at the University of Vermont and Salve Regina University, she joined the faculty of Salve Regina University in 2015.
Dr. Axen loosely classifies herself as an evolutionary ecologist, with a current focus on how organisms use their DNA to deal with different kinds of stress. The combinations of genes an individual has are important in determining how that organism looks and functions. Understanding how DNA is turned on or off, and expressed, is important for discovering the best ways to treat disease, save endangered species, improve agriculture, and predicting how organisms will deal with stress. DNA can change over time, but often stressors happen on a shorter timescale, and organisms must use their genetic tools in different ways to be successful. As a scientist, Dr. Axen tries to understand how an organism uses its DNA to deal with different kinds of stress by investigating two different areas. In the first project she to understand how social animals deal with easily transmissible diseases, like COVID-19, by looking at the relationships between pathogens, social behavior, and genes. In this National Science Foundation funded work, she uses ant colonies, which are highly social and mimic our behavior in myriad ways, as a model for human societies. In her second set of investigations, she seeks to better understand long term outcomes of climate change on living systems by looking at how the environment in which an organism grows up affects its ability to use its DNA to cope with heat/cold stress. In these experiments she uses wild caught fruit flies from places like Colorado, Vermont, Rhode Island, California, Arizona, and Hawaii.
Melise C. Lecheta, David N. Awde, Thomas S. O’Leary, Laura N. Unfried, Nicholas A. Jacobs, Miles H. Whitlock, Eleanor McCabe, Beck Powers, Katie Bora, James S. Waters, Heather J. Axen, Seth Frietze, Brent L. Lockwood, Nicholas M. Teets and Sara H. Cahan
Abstract: Thermal tolerance of an organism depends on both the ability to dynamically adjust to a thermal stress and preparatory developmental processes that enhance thermal resistance. However, the extent to which standing genetic variation in thermal tolerance alleles influence dynamic stress responses vs. preparatory processes is unknown. Here, using the model species Drosophila melanogaster, we used a combination of Genome Wide Association mapping (GWAS) and transcriptomic profiling to characterize whether genes associated with thermal tolerance are primarily involved in dynamic stress responses or preparatory processes that influence physiological condition at the time of thermal stress. To test our hypotheses, we measured the critical thermal minimum (CTmin) and critical thermal maximum (CTmax) of 100 lines of the Drosophila Genetic Reference Panel (DGRP) and used GWAS to identify loci that explain variation in thermal limits. We observed greater variation in lower thermal limits, with CTmin ranging from 1.81 to 8.60°C, while CTmax ranged from 38.74 to 40.64°C. We identified 151 and 99 distinct genes associated with CTmin and CTmax, respectively, and there was strong support that these genes are involved in both dynamic responses to thermal stress and preparatory processes that increase thermal resistance. Many of the genes identified by GWAS were involved in the direct transcriptional response to thermal stress (72/151 for cold; 59/99 for heat), and overall GWAS candidates were more likely to be differentially expressed than other genes. Further, several GWAS candidates were regulatory genes that may participate in the regulation of stress responses, and gene ontologies related to development and morphogenesis were enriched, suggesting many of these genes influence thermal tolerance through effects on development and physiological status. Overall, our results suggest that thermal tolerance alleles can influence both dynamic plastic responses to thermal stress and preparatory processes that improve thermal resistance. These results also have utility for directly comparing GWAS and transcriptomic approaches for identifying candidate genes associated with thermal tolerance.
Lecheta MC, Awde DN, O’Leary TS, Unfried LN, Jacobs NA, Whitlock MH, McCabe E, Powers B, Bora K, Waters JS,
Axen HJ, Frietze S, Lockwood BL, Teets NM and Cahan SH (2020) Integrating GWAS and Transcriptomics to Identify
the Molecular Underpinnings of Thermal Stress Responses in Drosophila melanogaster. Frontiers in Genetics. 11:658.
Open Access: DOI 10.3389/fgene.2020.00658
Lori Stevens, Raquel Asunción Lima-Cordón, Sara Helms Cahan, Patricia L. Dorn, M. Carlota Monroy, Heather J. Axen, Andrew Nguyen, Yainna Hernáiz-Hernánde, Antonieta Rodas, Silvia A. Justi
Abstract: Assays for parasite detection in insect vectors provide important information for disease control. American Trypanosomiasis (Chagas disease) is the most devastating vector-borne illness and the fourth most common in Central America behind HIV/AIDS and acute respiratory and diarrheal infections (Peterson et al., 2019). Under-detection of parasites is a general problem which may be influenced by parasite genetic variation; however, little is known about the genetic variation of the Chagas parasite, especially in this region. In this study we compared six assays for detecting the Chagas parasite, Trypanosoma cruzi: genomic reduced representation sequencing (here referred to as genotype-by-sequencing or GBS), two with conventional PCR (i.e., agarose gel detection), two with qPCR, and microscopy. Our results show that, compared to GBS genomic analysis, microscopy and PCR under-detected T. cruzi in vectors from Central America. Of 94 samples, 44% (50/94) were positive based on genomic analysis. The lowest detection, 9% (3/32) was in a subset assayed with microscopy. Four PCR assays, two with conventional PCR and two with qPCR showed intermediate levels of detection. Both qPCR tests and one conventional PCR test targeted the 195 bp repeat of satellite DNA while the fourth test targeted the 18S gene. Statistical analyses of the genomic and PCR results indicate that the PCR assays significantly under detect infections of Central American T. cruzi genotypes.
Lori Stevens, Raquel Asunción Lima-Cordón, Sara Helms Cahan, Patricia L. Dorn, M. Carlota Monroy, Heather J.
Axen, Andrew Nguyen, Yainna Hernáiz-Hernánde, Antonieta Rodas, Silvia A. Justi, Catch me if you can: Underdetection of Trypanosoma cruzi (Kinetoplastea: Trypanosomatida) infections in Triatoma dimidiata s.l. (Hemiptera: Reduviidae) from Central America, Acta Tropica, Volume 224, 2021, 106130, ISSN 0001-706X
Open Access: DOI 10.1016/j.actatropica.2021.106130