Biology subjects

Wahl, G. M.

Publications and source records attributed to Wahl, G. M..

6 recordsLinked to original sources

bioRxiv2024

The molecular chronology of mammary epithelial cell fate switching

The adult mammary gland is maintained by lineage-restricted progenitor cells through pregnancy, lactation, involution, and menopause. Injury resolution, transplantation-associated mammary gland reconstitution, and tumorigenesis are unique exceptions, wherein mammary basal cells gain the ability to reprogram to a luminal state. Here, we leverage newly developed cell-identity reporter mouse strains, and time-resolved single-cell epigenetic and transcriptomic analyses to decipher the molecular programs underlying basal-to-luminal fate switching in vivo. We demonstrate that basal cells rapidly reprogram toward plastic cycling intermediates that appear to hijack molecular programs we find in bipotent fetal mammary stem cells and puberty-associatiated cap cells. Loss of basal-cell specifiers early in dedifferentiation coincides with activation of Notch and BMP, among others. Pharmacologic blockade of each pathway disrupts basal-to-luminal transdifferentiation. Our studies provide a comprehensive map and resource for understanding the coordinated molecular changes enabling terminally differentiated epithelial cells to transition between cell lineages and highlights the stunning rapidity by which epigenetic reprogramming can occur in response to disruption of tissue structure.

cell biology↗

bioRxiv2024

LHPP expression in triple-negative breast cancer promotes tumor growth and metastasis by modulating the tumor microenvironment

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic form of breast cancer that lacks an effective targeted therapy. To identify new therapeutic targets, we investigated the phosphohistidine phosphatase, LHPP, which has been implicated in the development of several types of cancer. However, the full significance of LHPP in cancer progression remains unclear due to our limited understanding of its molecular mechanism. We found that levels of the LHPP phosphohistidine phosphatase were significantly increased in human breast cancer patients compared to normal adjacent tissues, with the highest levels in the TNBC subtype. When LHPP was knocked out in the MDA-MB-231 human TNBC cell line, cell proliferation, wound healing capacity, and invasion were significantly reduced. However, LHPP knockout in TNBC cells did not affect the phosphohistidine protein levels. Interestingly, LHPP knockout in MDA-MB-231 cells delayed tumor growth and reduced metastasis when orthotopically transplanted into mouse mammary glands. To investigate LHPPs role in breast cancer progression, we used next-generation sequencing and proximity-labeling proteomics, and found that LHPP regulates gene expression in chemokine-mediated signaling and actin cytoskeleton organization. Depletion of LHPP reduced the presence of tumor-infiltrating macrophages in mouse xenografts. Our results uncover a new tumor promoter role for LHPP phosphohistidine phosphatase in TNBC and suggest that targeting LHPP phosphatase could be a potential therapeutic strategy for TNBC.

cancer biology↗

bioRxiv2021

Loss of epigenetic regulation disrupts lineage integrity, reactivatesmultipotency and promotes breast cancer

Systematically investigating the scores of genes mutated in cancer and discerning real drivers from inconsequential bystanders is a prerequisite for Precision Medicine, but remains challenging. Here, we developed a somatic CRISPR/Cas9 mutagenesis screen to study 215 recurrent long-tail breast cancer genes, which revealed epigenetic regulation as major tumor suppressive mechanism. We report that core or accessory components of the COMPASS histone methylase complex including KMT2C, KDM6A, BAP1 and ASXL2 ("EpiDrivers") cooperate with PIK3CAH1047R to transform mouse and human breast epithelial cells. Mechanistically, we find that Cre-mediated activation of PIK3CAH1047R elicited an aberrant alveolar lactation program in luminal cells, which was exacerbated upon loss of EpiDrivers. Remarkably, EpiDriver loss in basal cells also triggered an alveolar-like lineage conversion and accelerated formation of luminal-like tumors, suggesting a basal origin for luminal tumors. As EpiDrivers are mutated in 39% of human breast cancers, lineage infidelity and lactation mimicry may significantly contribute to early steps of breast cancer progression. Statement of significanceInfrequently mutated genes comprise most of the mutational burden in breast tumors but are poorly understood. In-vivo CRISPR screening identified functional tumor suppressors that converged on epigenetic regulation. Loss of epigenetic regulators accelerated tumorigenesis and revealed lineage infidelity and aberrant expression of lactation genes as potential early events in tumorigenesis.

cancer biology↗

bioRxiv2019

Induction of pancreatic tumor-selective ferroptosis through modulation of cystine import

Pancreatic ductal adenocarcinoma (PDA) is the third-leading cause of cancer mortality in the US and is highly resistant to classical, targeted, and immune therapies. We show that human PDA cells are dependent on the provision of exogenous cystine to avert a catastrophic accumulation of lipid reactive oxygen species (ROS) that, left unchecked, leads to ferroptotic cell death, both in vitro and in vivo. Using a dual-recombinase genetically engineered model, we found that acute deletion of Slc7a11 led to tumor-selective ferroptosis, tumor stabilizations/regressions, and extended overall survival. The mechanism of ferroptosis induction in PDA cells required the concerted depletion of both glutathione and coenzyme A, highlighting a novel branch of ferroptosis-relevant metabolism. Finally, we found that cystine depletion in vivo using the pre-IND agent cyst(e)inase phenocopied Slc7a11 deletion, inducing tumor-selective ferroptosis and disease stabilizations/regressions in the well-validated KPC model of PDA.\n\nOne Sentence SummaryGenetic and pharmacological targeting of cystine import induces pancreatic cancer-selective ferroptosis in vivo.

cancer biology↗

bioRxiv2019

Single-cell chromatin accessibility analysis of mammary gland development reveals cell state transcriptional regulators and cellular lineage relationships

It has only recently become possible to obtain single-cell level resolution of the epigenetic changes that occur during organ development. We reasoned that precision single-cell chromatin accessibility mapping of mammary gland development could provide needed insight into the epigenetic reprogramming and transcriptional regulators involved in normal mammary gland development. Here, we provide the first single-cell resource of chromatin accessibility for murine mammary development from the peak of fetal mammary stem cell (fMaSC) functional activity in late embryogenesis to the differentiation of adult basal and luminal cells. We find that the chromatin landscape within individual cells predicts both gene accessibility and transcription factor activity, and we present a web application as a scientific resource for facilitating future analyses. Strikingly, these single-cell chromatin profiling data reveal that fMaSCs can be separated into basal-like and luminal-like lineages, providing evidence of early lineage segregation prior to birth. Such distinctions were not evident in analyses of single-cell transcriptomic data.

genomics↗

bioRxiv2018

Facile real time detection of membrane colocalization of RAS superfamily GTPase proteins in living cells

Members of the RAS family of GTPases (KRAS4A, KRAS4B, HRAS, and NRAS) are the most frequently mutated oncogenes in human cancers. The CAAX motif in the C-terminal hypervariable region (HVR-CAAX domain) contains the cysteine residue that is critical for protein prenylation that enables RAS protein membrane localization, homodimer/oligomer formation, and activation of effector signaling and oncogenic activity. However, it remains unclear if RAS can interact with other prenylated proteins, and if so, how this impacts RAS function. Here we use a newly developed quantifiable Recombinase enhanced Bimolecular Luciferase Complementation strategy (ReBiL2.0) to investigate some of the requirements for RAS superfamily small GTPase protein interactions, and whether this requires cell membrane localization. ReBiL enables such analyses to be done at physiologic expression levels in living cells. Our results confirm that the C-terminal prenylated HVR-CAAX domain is sufficient to direct KRAS and heterologous proteins to colocalize in the cell membrane. We discovered that KRAS also colocalizes with a subset of small GTPase superfamily members including RAC1, RAC2 and DIRAS3 in a prenylation-dependent manner. KRAS colocalization or co-clustering with heterologous proteins can impact KRAS downstream signaling. ReBiL2.0 thus provides a rapid, simple and straightforward method to identify and characterize the colocalization of membrane-associated proteins and to discover agonists and antagonists thereof.

cancer biology↗