| School of Biological Sciences | Georgia Institute of Technology | Atlanta, GA | Georgia Institute of Technology

In this talk, Rohr will present nature-based solutions that address interconnected challenges among disease, agriculture, water, and poverty. His research shows that removing invasive aquatic vegetation in West African waterways can reduce schistosomiasis infections while improving water access and agricultural productivity. By converting this vegetation into low-cost livestock feed, compost, and fuel for biodigesters that produce fertilizer and off-grid energy, communities gain profitable incentives to sustain the nature-based solution. Building on these successes, Rohr’s team will expand efforts using climate-smart agriculture, renewable energy, and remote sensing to enhance resilience and equity across Africa and beyond, offering scalable, win-win strategies for global planetary health.

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Dr. Williamson will discuss her research on birds that make extreme seasonal shifts in elevation during migration and how these movements affect ecology, evolution, and physiology. She will highlight her lab’s work on giant hummingbirds (Patagona spp.) in the Andes, where her team has combined movement tracking, genomics, and field physiological experiments to uncover extreme daily movements, a spectacular long-distance migratory journey involving an extreme elevational ascent, and cryptic speciation between the world’s largest hummingbirds.

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Biodiversity begins with divergence, but divergence does not always last. Populations become isolated and reconnect, lineages exchange genes, and newly formed lineages can either persist for millions of years or disappear almost as quickly as they arise. Why, then, do some parts of the Tree of Life produce extraordinary diversity while others do not? I explore this question across biological scales, from populations to large evolutionary radiations. Using studies of vertebrates and desert plants, I ask what determines whether evolutionary differences arise, persist, and ultimately accumulate into biodiversity.

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Experimental evolution in vivo is a powerful approach to identify the selective pressures shaping bacterial adaptation during infection, yet how host immunity modulates these evolutionary trajectories remains a fundamental gap in infection biology. Applying whole-population genomic sequencing to replicate bacterial populations serially passaged through murine or porcine infection models, we demonstrate that niche-specific selective pressures produce convergent genetic adaptations, including parallel mutations modulating pneumococcal surface charge during colonization and prophage-mediated disruption of global regulators during chronic Pseudomonas aeruginosa wound infection. Host immune status critically shapes these trajectories, as neutropenic hosts broaden mutational pathways to fluoroquinolone resistance in Acinetobacter baumannii while functional immunity constrains the outgrowth of resistant variants. Most recently, we show that Streptococcus pneumoniae subjected to combined antibiotic and immune pressure evolves convergent mutations altering the RNA degradosome that confer broad-spectrum antibiotic tolerance through a bet-hedging transcriptional strategy influenced by host immune state. Together, these studies establish that in vivo experimental evolution provides a mechanistic roadmap for predicting genetic pathways to treatment failure and informing strategies to constrain the evolution of antimicrobial resistance.

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Genome-wide association studies have transformed our understanding of complex trait genetics, but most statistical methods assume relatively homogeneous ancestry. This leaves admixed individuals, whose genomes are mosaics of ancestry tracts from multiple continental populations, frequently excluded from analysis due to concerns over population stratification. My lab addresses this gap by developing and applying tools leveraging local ancestry: a technique that assigns ancestral origin to each segment of the genome, rather than summarizing ancestry for individuals using a single label.

I will present work spanning three areas. First, a simulation-based framework establishing best practices for local ancestry inference across reference panel compositions, admixture demographics, and genotype discovery approaches. Second, our recently published method Tractor-Mix, a local ancestry-informed mixed model that extends our earlier Tractor framework to enable well-calibrated GWAS in admixed cohorts with relatedness. We demonstrate Tractor-Mix’s performance across multiple large datasets including the UK Biobank, Yale-Penn cohort, and Mexico City Prospective Study, finding novel loci missed by traditional methods and better determining the ancestry driving unique signals. Third, I will describe our application of local ancestry inference across more than 140,000 genomes in gnomAD, which substantially refines ancestry-specific allele frequency estimates with direct implications for clinical variant interpretation. Together, this work illustrates how ancestry-aware statistical methods can improve genetic discovery, risk prediction, and variant interpretation across the full range of human genetic diversity.

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Our ultimate research goal is to develop clinically translatable nucleic acid therapeutics and vaccines. In this talk, we will discuss our research in the engineering of circular RNA (circRNA) therapeutics and vaccines, as well as the development of their delivery systems, for versatile application in cancer immunotherapy, prevention of infectious diseases, and gene therapy of genetic diseases. circRNA vaccines are highly stable with sustained production of encoded proteins and peptides, which can be leveraged to promote the prophylactic or therapeutic efficacies while minimizing adverse side effects. Accompanied with circRNA engineering, novel lipid nanoparticles were developed to promote circRNA delivery, for example, to alveoli macrophages for promoting mucosal immunity, and to airway epithelial cells for the gene therapy of cystic fibrosis. Based on these, we will discuss 1) circRNA vaccines that elicit robust and long-lasting CD8+/CD4+ T cell responses for tumor combination immunotherapy; 2) pulmonary delivery of circRNA vaccines that elicit respiratory mucosal immunity for the prevention of viral infection and for the immunotherapy of lung metastatic melanoma; 3) pulmonary delivery of a circRNA encoding a full-length wildtype cystic fibrosis transmembrane conductance regulator (CFTR) protein for the gene therapy of cystic fibrosis; and 4) non-coding circular guide RNA have been developed for ADAR and Cas13d gene editing.