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The Rohlfs lab is excited to host this week's IEE seminar speaker, Dr. Melissa Gymrek from UC San Diego. Dr. Gymrek's lab is interested in genotype-phenotype associations, with a particular emphasis on tandem repeat variation and its contribution to disease in humans. We have a rough schedule for her visit this Friday. Please sign up to meet with her! 

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From Dr. Gymrek's Webpage:Our overall goal is to understand genetic variants that underlie human disease and how their effects vary across different populations. We are a multidisciplinary lab and include both computational and wet lab biologists. We are particularly interested in repetitive DNA variants known as tandem repeats (TRs). Major research areas include (1) developing computational tools for analyzing TR variation in biobank-scale genomic datasets, (2) identifying TRs contributing to both rare and complex traits, (3) studying mutation and selection processes at TRs within and across species, (4) understanding how the effects of TRs and other genetic variants differ across human populations, and (5) using high-throughput experimental techniques to study the impacts of TR and other variants on molecular and cellular phenotypes in healthy and disease states.

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Meeting ID: 926 6205 2101

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Meeting ID: 926 6205 2101

Title: Not All Bad News: Minor Genomic Impacts of Population Declines in Brown Bears

Abstract: Brown bears (Ursus arctos) were once widespread across the Northern Hemisphere but have experienced recent and severe population declines. Present-day North American diversity and distribution of bears remain poorly understood due to conflicting hypotheses about colonization timing across Beringia and subsequent population connectivity. To address this, we generated whole-genome sequences from 268 brown bears spanning all extant populations in the contiguous United States and much of Alaska and Canada. Demographic analyses reveal three distinct waves of colonization: an initial wave during Marine Isotope Stage 4 (~57,000–71,000 years ago), a second during the Last Glacial Maximum (LGM; ~14,000–29,000 years ago), and a final wave near the end of the LGM (~12,000 years ago). Although populations were likely connected following deglaciation, populations have declined sharply over the last ~250 years. Though isolated populations show evidence of recent inbreeding, genetic load remains low. Sex chromosome analyses indicate male-biased dispersal, though anthropogenic barriers limit gene flow in both sexes. We also identify selection signals in genes associated with hibernation and diet, suggesting potential adaptive responses relevant to future persistence. Overall, our results clarify colonization history and provide a comprehensive view of the current genetic health of North American brown bears.  

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Meeting ID: 926 6205 2101

Talk title: “Predicting genotype by disentangling the underlying evolutionary forces.”

Talk Abstract:
The genotypes we observe in biology are not shaped by any one process. Alleles often experience competing selection pressures, while the mutations that introduce sequence variation differ in both their fitness effects and their probabilities of arising in the first place. How do these factors combine quantitatively to determine evolutionary outcomes? I address this question using a combination of experimental and computational approaches. In one line of work, I study mutant mitochondrial genome (mtDNA) variants that are stably co-transmitted alongside wildtype mtDNA despite harming host fitness, termed “selfish mtDNA.” Using C. elegans as a model system, I developed experiments to isolate and measure selection on mtDNA at different levels of biological organization. These measurements showed how selfish transmission within the germline combines with selection forces favoring wildtype mtDNA, revealing an astonishing diversity in the evolutionary mechanisms that maintain long-term coexistence of selfish and wildtype mtDNA. In parallel, my ongoing work combines population-genetic modeling with experimental evolution data to understand how selection interacts with the input of new mutations to shape the evolutionary paths that protein sequences follow. Together, these approaches provide a quantitative framework for disentangling the evolutionary forces underlying the genotypes we observe.

Join Zoom Meeting
Meeting ID: 926 6205 2101

Join Zoom Meeting
Meeting ID: 926 6205 2101

Join Zoom Meeting
Meeting ID: 926 6205 2101

Fall retreat to share research, discuss vision for department and socialize.