Biology subjects

Weigel, R. J.

Publications and source records attributed to Weigel, R. J..

4 recordsLinked to original sources

bioRxiv2025

MITF-Independent Melanocyte Progenitors are Highly Susceptible to GNAQ-induced Uveal Melanoma in Adult Zebrafish

Melanocytes reside in diverse microenvironments that influence their susceptibility to oncogenic transformation; however, investigation of rare melanoma subsets has been limited by the lack of suitable pre-clinical animal models. Here, we developed a primary, immune-competent zebrafish model to study uveal melanoma (UM) using choroidal melanocyte-targeted injection and electroporation of plasmids encoding human GNAQQ209L together with CRISPR/Cas9 cassettes for somatic tumor suppressor gene deletion. Single-cell transcriptional profiling of primary melanocytes and melanoma derived from the eye and skin revealed distinct transcriptional programs, with epithelial-to-mesenchymal transition pathways enriched in ocular tumors. In addition, choroidal fibroblasts from tumor-bearing eyes exhibited marked transcriptional changes, including increased fibronectin and collagen expression, consistent with stromal remodeling. Given prior associations between mitfa loss and accelerated GNAQQ209L tumor onset, the model was applied to determine whether melanocyte differentiation state contributes to the emergence of GNAQ-driven tumors. The increased susceptibility resulted from expansion of Mitfa-independent melanocyte progenitor populations in germline mitfa mutant zebrafish, rather than somatic mitfa loss in differentiated melanocytes, as conditional, melanocyte-specific mitfa deletion in adult zebrafish did not accelerate tumor growth. Furthermore, pax3a-positive melanocyte progenitor cells in mitfa-deficient zebrafish embryos and adult eyes and skin were highly susceptible to transformation induced by GNAQQ209L but not BRAFV600E. Analogous PAX3 positive populations were also identified in mouse and human single-cell transcriptomic datasets. Collectively, these findings establish a critical role for Mitfa-independent melanocyte progenitors in UM pathogenesis. Statement of SignificanceChoroid-targeted GNAQQ209L expression induces anatomically correct uveal melanoma in adult zebrafish, with germline mitfa deletion expanding mitfa-independent melanocyte progenitors with enhanced susceptibility that are transcriptionally distinct from the subpopulation transformed by BRAFV600E.

cancer biology↗

bioRxiv2024

An MITF- and mTOR-dependent FLCN pathway suppresses TFE3-driven metastasis in melanoma

Melanoma cells have the ability to switch from a melanocytic and proliferative state to a mesenchymal and invasive state and back again. This plasticity drives intra-tumoral heterogeneity, progression, and therapeutic resistance. Microphthalmia-associated Transcription Factor (MITF) promotes the melanocytic/proliferative phenotype, but factors that drive the mesenchymal/invasive phenotype and the mechanisms that effect the switch between cell states are unclear. Here, we identify the MITF paralog TFE3 and the non-canonical mTORC1 pathway as regulators of the mesenchymal state. We show that TFE3 expression drives the metastatic phenotype in melanoma cell lines and tumors. Deletion of TFE3 in MITF-low melanoma cell lines suppresses their ability to migrate and metastasize. Further, MITF suppresses the mesenchymal phenotype by directly or indirectly activating expression of FNIP1, FNIP2, and FLCN, which encode components of the non-canonical mTORC1 pathway, thereby promoting cytoplasmic retention and lysosome-mediated degradation of TFE3. These findings highlight a molecular pathway controlling melanoma plasticity and invasiveness.

cancer biology↗

bioRxiv2022

Blocking Gi/o-coupled signaling eradicates cancer stem cells and sensitizes breast tumors to HER2-targeted therapies to inhibit tumor relapse

Cancer stem cells (CSCs) are a small subpopulation of cells within tumors that are resistant to anti-tumor therapies, making them a likely origin of tumor relapse after treatment. In many cancers including breast cancer, CSC function is regulated by G protein-coupled receptors (GPCRs), making GPCR signaling an attractive target for new therapies designed to eradicate CSCs. Yet, CSCs overexpress multiple GPCRs that are redundant in maintaining CSC function, so it is unclear how to target all the various GPCRs to prevent relapse. Here, in a model of HER2+ breast cancer (i.e., transgenic MMTV-Neu mice), we were able to block tumorsphere- and tumor-forming capability of CSCs by targeting GPCRs coupled to Gi/o proteins (Gi/o-GPCRs). Similarly, in HER2+ breast cancer cells, blocking signaling downstream of Gi/o-GPCRs in the PI3K/AKT and Src pathways also enhanced HER2-targeted elimination of CSCs. In a proof-of-concept study, when CSCs were selectively ablated (via a suicide gene construct), loss of CSCs from HER2+ breast cancer cell populations mimicked the effect of targeting Gi/o-GPCR signaling, suppressing their capacity for tumor initiation and progression and enhancing HER2-targeted therapy. Thus, targeting Gi/o-GPCR signaling in HER2+ breast cancer is a promising approach for eradicating CSCs, enhancing HER2+ targeted therapy and blocking tumor reemergence.

cancer biology↗

bioRxiv2020

AP-2γ is Required for Maintenance of Pluripotent Mammary Stem Cells

Mammary gland ductal morphogenesis depends on the differentiation of mammary stem cells (MaSCs) into basal and luminal lineages. The AP-2{gamma} transcription factor, encoded by Tfap2c, has a central role in mammary gland development but its effect in mammary lineages and specifically MaSCs is largely unknown. Herein, we utilized an inducible, conditional knockout of Tfap2c to elucidate the role of AP-2{gamma} in maintenance and differentiation of MaSCs. Loss of AP-2{gamma} in the basal epithelium profoundly altered the transcriptomes and decreased the number of cells within several clusters of mammary epithelial cells, including adult MaSCs and luminal progenitors. AP-2{gamma} regulated the expression of genes known to be required for mammary development including C/EBP{beta}, I{kappa}B, and Rspo1. As a result, AP-2{gamma}-deficient mice exhibited repressed mammary gland ductal outgrowth and inhibition of regenerative capacity. The findings demonstrate that AP-2{gamma} is required for maintenance of pluripotent MaSCs and their ability to develop mammary gland structures. HighlightsO_LIAP-2{gamma}-deficient mice exhibited repressed ductal outgrowth and regenerative capacity C_LIO_LILoss of AP-2{gamma} reduced the number of mammary stem and luminal progenitor cells C_LIO_LIAP-2{gamma} target genes, including C/EBP{beta}, I{kappa}B, and Rspo1, regulate mammary development C_LIO_LIAP-2{gamma} is required for maintenance of pluripotent mammary stem cells C_LI eTOC blurbGu, Cho and colleagues utilized a conditional knockout of Tfap2c to examine transcriptional effects of AP-2{gamma} on mammary stem cells. Single cell analysis demonstrated that AP-2{gamma}-deficient mice have decreased numbers of mammary stem cells and alteration of genes required for mammary development including C/EBP{beta}, I{kappa}B, and Rspo1. They demonstrate that AP-2{gamma} is necessary for maintenance of pluripotent mammary stem cells.

developmental biology↗