The germline is the only cell lineage capable of giving rise to egg and sperm cells, but mechanisms driving specification of the germline in the human embryo remain poorly understood due to scarce access to early embryonic tissue. Previous work has established that specification of primordial germ cells (PGCs)—the precursor population to eggs and sperm—is influenced by Transforming Growth Factor β (TGF-β) and Fibroblast Growth Factor (FGF) signaling. However, the roles of these signals remain largely uncharacterized within the specification niche. Here, we utilized a highly defined in vitro germ cell model to robustly specify PGCs. By perturbing the makeup of growth factors within the model, we showed that TGF-β and FGF signaling are key drivers for PGCs specification, and that the combination of both signals early on during this dynamic process was crucial for specifying PGCs and preventing cells from adopting amniotic cell fate. Overall, these results elucidated a novel finding on the importance of the TGF-β subfamily (TGF-β1/2/3) as a key driver of PGC fate induction and its cooperative behavior with FGF signaling.

Liver ischemia-reperfusion injury occurs when blood flow is temporarily blocked and then restored, creating oxygen stress that can damage liver tissue after transplantation. This project investigated whether hypoxia inducible factor 2α, or HIF2α, helps coordinate the liver’s molecular response to this stress by regulating alternative RNA splicing and downstream injury pathways. My work focused on testing how loss of HIF2α changes specific splicing events and protein-level stress responses in a warm hepatic ischemia-reperfusion injury mouse model. Through PCR-based analysis, I examined splice isoform changes in stress- and inflammation-related genes, including CEACAM1, HO-1, and PTBP1. These results suggested that HIF2α is needed to maintain normal alternative splicing during ischemic stress, especially for CEACAM1, where HIF2α loss was associated with reduced expression of the anti-inflammatory CEACAM1-S isoform. Western blot analysis further showed that HIF2α deficiency was linked to disrupted autophagy signaling during reperfusion, connecting altered splicing regulation to broader injury-response pathways. Together, these findings support a mechanism in which HIF2α protects the liver during ischemic stress by shaping both RNA splicing programs and protein signaling responses. The significance of this project is that it points to alternative splicing as a significant effect of injury and it may be an active molecular pathway through which the liver responds to, and potentially limits, transplant-related damage.

Hair cells of the inner ear of the American bullfrog play an important role in the auditory system. They perform the first step in active detection of sound by converting mechanical deflections into electric signals that are transmitted to neurons. Studying the living hair cells ex vivo provides valuable information into the mechanisms underlying sound detection. In this experiment, we studied the nonlinear dynamics of hair bundle oscillations and drove the cells with a fluid jet. We developed a strong ex vivo preparation of the utricle and sacculus, which are both auditory organs of a bullfrog. The utricle detects linear acceleration and head orientation while the sacculus detects low frequency vibrations. While most of the cells in the utricle didn’t seem to be oscillating, we found that most of the oscillations found were classified as spiking oscillations with a few regular oscillations. Regular oscillations displayed stable oscillations with a clear frequency, while spiking oscillations were inactive with sudden bursts of oscillations. We then drove the cells with a fluid jet device to watch how the cells reacted.

Cutaneous melanoma is the most aggressive form of skin cancer and can be especially difficult to treat once it metastasizes. The tumor microenvironment (TME) plays an important role in tumor development and progression. Previous research from the Coller Lab demonstrated that TME from melanoma patients had increased levels of autophagy marker LC3, which suggests autophagy may influence tumor progression. Autophagy is a process by which intracellular molecules are degraded, recycled, and repurposed, and also plays a role in immune cell activity in tumors. Systemic autophagy inactivation from earlier Coller Lab studies resulted in smaller tumors, indicating its importance in supporting tumor growth in some contexts. This project aims to examine how autophagy depletion affects T cell mediated anti-tumor response in the B16F10 melanoma model. We use a system in which autophagy is selectively disrupted in stromal cells within the TME. Previous observations suggest that T cells in autophagy-deficient environments may be more primed to respond to B16F10 tumors. To explore the role of specific T cell populations, we performed antibody depletions of CD4+ and CD8+ T cells and monitored tumor growth. These experiments aim to determine how specific T cell subsets contribute to reduced tumor growth in the absence of autophagy. Understanding these interactions will clarify how autophagy influences anti-tumor immunity and could inform future strategies for improving immune-based therapies for melanoma.