Biology subjects

Powell, D. J.

Publications and source records attributed to Powell, D. J..

5 recordsLinked to original sources

bioRxiv2025

Neuronal cell adhesion molecule (NRCAM) variant defined by microexon skipping is an essential, antigenically distinct, and targetable surface proteoform in high-grade glioma

To overcome the paucity of known tumor-specific surface antigens in pediatric high-grade glioma (pHGG), we contrasted splicing patterns in pHGGs and normal brain samples. Among alternative splicing events affecting extracellular protein domains, the most pervasive alteration was the skipping of [≤]30 nucleotide-long exons. Several of these skipped microexons mapped to L1-IgCAM family members, such as NRCAM. Bulk and single-nuclei short- and long-read RNA-seq revealed uniform skipping of NRCAM microexons 5 and 19 in virtually every pHGG sample. Importantly, the {Delta}ex5{Delta}ex19 (but not the full-length) NRCAM proteoform was essential for pHGG cell migration and invasion in vitro and tumor growth in vivo. We developed a monoclonal antibody selective for {Delta}ex5{Delta}ex19 NRCAM and demonstrated that "painting" of pHGG cells with this antibody enables killing by T cells armed with an FcRI-based universal immune receptor. Thus, pHGG-specific NRCAM and possibly other L1-IgCAM proteoforms are promising and highly selective targets for adoptive immunotherapies.

cancer biology↗

bioRxiv2021

Systematic analysis of CD39, CD103, CD137 and PD-1 as biomarkers for naturally occurring tumor antigen-specific TILs

The detection of tumor-specific T cells in solid tumors is integral to the interrogation of endogenous antitumor responses and to the advancement of downstream therapeutic applications, such as checkpoint immunotherapy and adoptive cell transfer. A number of biomarkers are reported to identify endogenous tumor-specific tumor infiltrating lymphocytes (TILs), namely CD137, PD-1, CD103, and CD39, however a direct comparison of these molecules has yet to be performed. Here, we evaluate these biomarkers in primary human high-grade serous ovarian tumor samples using single-cell mass cytometry to characterize and compare their relative phenotypic profiles, as well as their response to autologous tumor cells ex vivo. CD137+, PD-1+, CD103+, and CD39+ TILs are all detectable in tumor samples with CD137+ TILs being the least abundant. PD-1+, CD103+, and CD39+ TILs all express a subset of CD137+ cells, while CD137+ TILs highly co-express the aforementioned markers. CD137+ TILs exhibit the highest expression of cytotoxic effector molecules, such as IFN{gamma} and Granzyme B, compared to PD-1+, CD103+ or CD39+ TILs. Removal of CD137+ TILs from PD-1+, CD103+, or CD39+ TILs results in lower secretion of IFN{gamma} in response to autologous tumor stimulation, while CD137+ TILs highly secrete IFN{gamma} in an HLA-dependent manner. CD137+ TILs exhibited an exhausted phenotype with CD28 co-expression, suggestive of antigen recognition and receptiveness to reinvigoration via immune checkpoint blockade. Together, our findings demonstrate that the antitumor abilities of PD-1+, CD103+, and CD39+ TILs are mainly derived from a subset of TILs expressing CD137, implicating CD137 is a more selective biomarker for naturally occurring tumor-specific TILs.

immunology↗

bioRxiv2021

Epigenetic state determines inflammatory sensing in neuroblastoma

Immunotherapy has revolutionized cancer treatment, but many cancers are not impacted by currently available immunotherapeutic strategies. Here, we investigated inflammatory signaling pathways in neuroblastoma, a classically "cold" pediatric cancer. By testing the functional response of a panel of 20 diverse neuroblastoma cell lines to three different inflammatory stimuli, we found that all cell lines have intact interferon signaling and all but one lack functional cGAS-STING signaling. However, toll-like receptor (TLR) signaling, particularly through TLR3, was heterogeneous. Six cell lines showed robust response, five of which are in the mesenchymal epigenetic state, while all 14 unresponsive cell lines are in the adrenergic state. Genetically switching the adrenergic BE2(c) cell line towards the mesenchymal state fully restored TLR responsiveness. In responsive cells, TLR3 activation results in the secretion of pro-inflammatory cytokines, enrichment of inflammatory transcriptomic signatures, and increased tumor killing by T-cells in vitro. Using single cell RNA sequencing data, we show that human neuroblastoma cells with stronger mesenchymal signatures have a higher basal inflammatory state, demonstrating intra-tumoral heterogeneity in inflammatory signaling that has significant implications for immunotherapeutic strategies in this aggressive childhood cancer.

cancer biology↗

bioRxiv2020

Degenerate circuits use distinct mechanisms to respond similarly to the same perturbation

There is considerable flexibility embedded within neural circuits. For example, separate modulatory inputs can differently configure the same underlying circuit but these different configurations generate comparable, or degenerate, activity patterns. However, little is known about whether these mechanistically different circuits in turn exhibit degenerate responses to the same inputs. We examined this issue using the crab (Cancer borealis) stomatogastric nervous system, in which stimulating the modulatory projection neuron MCN1 and bath applying the neuropeptide CabPK II elicit similar gastric mill (chewing) rhythms in the stomatogastric ganglion, despite differentially configuring the same neural circuit. We showed previously that bath applying the peptide hormone CCAP or stimulating the muscle stretch-sensitive sensory neuron GPR during the MCN1-elicited gastric mill rhythm selectively prolongs the protraction or retraction phase, respectively. Here, we found that these two influences on the CabPK-rhythm elicited some unique and unexpected consequences compared to their actions on the MCN1-rhythm. For example, in contrast to its effect on the MCN1-rhythm, CCAP selectively decreased the CabPK-rhythm retraction phase and thus increased the rhythm speed, whereas the CabPK-rhythm response to stimulating GPR during the retraction phase was similar its effect on the MCN1-rhythm (i.e. prolonging retraction). Interestingly, despite the comparable GPR actions on these degenerate rhythms, the underlying synaptic mechanism was distinct. Thus, degenerate circuits do not necessarily exhibit degenerate responses to the same influence, but when they do, it can occur via different underlying mechanisms. Significance StatementCircuits generating seemingly identical behaviors are often thought to arise from identical circuit states, as that is the most parsimonious explanation. Here we take advantage of an alternate scenario wherein a well-defined circuit with known connectivity generates similar activity patterns using distinct circuit states, via known mechanisms. The same peptide hormone modulation of these distinct circuit states produced divergent activity patterns, whereas the same sensory feedback altered these circuit outputs similarly but via different synaptic pathways. The latter observation limits the insights available from comparable studies in systems lacking detailed access to the underlying circuit.

neuroscience↗

bioRxiv2019

Rapid adaptation to elevated extracellular potassium in the pyloric circuit of the crab, Cancer borealis

Elevated [K+] is often used to alter excitability in neurons and networks by shifting the potassium equilibrium potential (EK) and, consequently, the resting membrane potential. We studied the effects of increased extracellular [K+] on the well-described pyloric circuit of the crab, Cancer borealis. A 2.5-fold increase in extracellular [K+] (2.5x[K+]) depolarized Pyloric Dilator (PD) neurons and resulted in short-term loss of their normal bursting activity. This period of silence was followed within 5-10 minutes by the recovery of spiking and/or bursting activity during continued superfusion of 2.5x[K+] saline. In contrast, when PD neurons were pharmacologically isolated from pyloric presynaptic inputs, they exhibited no transient loss of spiking activity in 2.5x[K+], suggesting the presence of an acute inhibitory effect mediated by circuit interactions. Action potential threshold in PD neurons hyperpolarized during an hour-long exposure to 2.5x[K+] concurrent with the recovery of spiking and/or bursting activity. Thus, the initial loss of activity appears to be mediated by synaptic interactions within the network, but the secondary adaptation depends on changes in the intrinsic excitability of the pacemaker neurons. The complex sequence of events in the responses of pyloric neurons to elevated [K+] demonstrates that electrophysiological recordings are necessary to determine both the transient and longer-term effects of even modest alterations of K+ concentrations on neuronal activity. Significance StatementSolutions with elevated extracellular potassium are commonly used as a depolarizing stimulus. Moreover, hyperkalemia is associated with a number of disease states, including epileptic seizures and brain traumas. We studied the effects of high [K+] saline on the well-described pyloric circuit of the crab stomatogastric ganglion. A 2.5-fold increase in extracellular [K+] led to a transient loss of activity in pyloric neurons that was not due to depolarization block. This was followed by a rapid increase in excitability and concurrent recovery of spiking and rhythmic bursting activity within minutes. These results suggest that effects of high [K+] on neuronal circuits can be complex and non-stationary.

neuroscience↗