Biology subjects

Spencer, S. A.

Publications and source records attributed to Spencer, S. A..

3 recordsLinked to original sources

bioRxiv2025

PD-1 regulates CD4+ T cell-mediated CD8+ T cell responses in the brain to balance viral control and neuroinflammation

Programmed cell death protein 1 (PD-1) is expressed by T cells during progressive multifocal leukoencephalopathy (PML), a life-threatening brain disease caused by the human-only JC polyomavirus. Why PD-1 blockade finds variable success in PML patients is unclear. Brain CD4+ and CD8+ T cells are PD-1high during mouse polyomavirus (MuPyV) encephalitis. Here, we show that PD-1 loss during MuPyV infection acts in a brain-autonomous manner to increase the magnitude of brain-infiltrating CD4+ and CD8+ T cells and the function of virus-specific CD8+ T cells; in concert, brain virus levels decline and neuroinflammation increases. Deletion of PD-1 in CD4+ T cells, but not CD8+ T cells, recapitulates effects of global PD-1 loss. Single-cell RNA sequencing shows that PD-1-deficient CD8+ T cells cluster as effectors while transcripts associated with proliferation and function are upregulated with loss of PD-1. Thus, CD4+ T cell-intrinsic PD-1 signaling balances antiviral defense against neural injury during polyomavirus CNS infection.

immunology↗

bioRxiv2023

Calcyphosine is a microtubule-associated protein required for spindle formation and function

Calcyphosine (CAPS) is a highly conserved but little explored calcium-binding protein that shows elevated expression in many forms of human cancer. Here we uncover a role for CAPS in spindle formation during mitosis. Our experiments suggest that CAPS is a microtubule-binding, spindle-associated protein that helps create the kinetochore fibers that bind and segregate chromosomes. Knockdown of CAPS causes a variety of defects during mitosis, including uncongressed chromosomes and multi-polar spindles, as well as high levels of apoptosis and a reduced mitotic index. We find that CAPS promotes microtubule bundling, both in vitro and in cells, and knockdown of CAPS leads to reduction of thick k-fibers in the mitotic spindle. The high level of CAPS observed in many forms of cancer suggests that CAPS may promote cell proliferation, but our results indicate that CAPS overexpression has little effect on the cell cycle. This suggests that the high level of CAPS expression may be a consequence of cancer, rather than a driving force for cell proliferation.

cell biology↗

bioRxiv2019

The MITF paralog tfec is required in neural crest development for fate specification of the iridophore lineage from a multipotent pigment cell progenitor

Understanding how fate specification of distinct cell-types from multipotent progenitors occurs is a fundamental question in embryology. Neural crest stem cells (NCSCs) generate extraordinarily diverse derivatives, including multiple neural, skeletogenic and pigment cell fates. Key transcription factors and extracellular signals specifying NCSC lineages remain to be identified, and we have only a little idea of how and when they function together to control fate. Zebrafish have three neural crest-derived pigment cell types, black melanocytes, light-reflecting iridophores and yellow xanthophores, which offer a powerful model for studying the molecular and cellular mechanisms of fate segregation. Mitfa has been identified as the master regulator of melanocyte fate. Here, we show that an Mitf-related transcription factor, Tfec, functions as master regulator of the iridophore fate. Surprisingly, our phenotypic analysis of tfec mutants demonstrates that Tfec also functions in the initial specification of all three pigment cell-types, although the melanocyte and xanthophore lineages recover later. We show that Mitfa represses tfec expression, revealing a likely mechanism contributing to the decision between melanocyte and iridophore fate. Our data is consistent with the long-standing proposal of a tripotent progenitor restricted to pigment cell fates. Moreover, we investigate activation, maintenance and function of tfec in multipotent NCSCs, demonstrating for the first time its role in the gene regulatory network forming and maintaining early neural crest cells. In summary, we build on our previous work to characterise the gene regulatory network governing iridophore development, establishing Tfec as the master regulator driving iridophore specification from multipotent progenitors, while shedding light on possible cellular mechanisms of progressive fate restriction.

developmental biology↗