Benjamin W. Darbro

Maintaining cardiac structure and function throughout the lifespan requires a delicate balance in carbon allocation between energetic and biosynthetic processes. At the nexus of this balance are prohibitins (PHB1, 2), which form a ring-like complex in mitochondrial and plasma membranes responsible for coordinating cellular growth, metabolism and autophagy. Here we describe how ablation of the PHB complex in cardiomyocytes of adult mice (cPHB1KO) causes unrestrained mechanistic target of rapamycin complex 1 (mTORC1) activity and a ‘Warburg-like’ reprogramming of glucose metabolism in heart toward enhanced de novo amino acid biosynthesis. These changes are accompanied by disruptions in mitochondrial Ca ²⁺ handling and impaired autophagy, leading to severe dilated cardiomyopathy and mortality within 12 weeks. Using pharmacological and nutritional approaches, we further show that mTORC1 inhibition attenuates pathologic cardiac remodeling only in female cPHB1KO mice. Our findings illustrate novel mechanisms linking the PHB complex with altered carbon flux and pathogenesis of cardiomyopathy.

The COVID-19 pandemic has caused substantial worldwide disruptions in health, economy, and society, manifesting symptoms such as loss of smell (anosmia) and loss of taste (ageusia), that can result in prolonged sensory impairment. Establishing the host genetic etiology of anosmia and ageusia in COVID-19 will aid in the overall understanding of the sensorineural aspect of the disease and contribute to possible treatments or cures. By using human genome sequencing data from the University of Iowa (UI) COVID-19 cohort (N = 187) and the National Institute of Health All of Us (AoU) Research Program COVID-19 cohort (N = 947), we investigated the genetics of anosmia and/or ageusia by employing feature selection techniques to construct a novel variant and gene prioritization pipeline, utilizing machine learning methods for the classification of patients. Models were assessed using a permutation-based variable importance (PVI) strategy for final prioritization of candidate variants and genes. The highest held-out test set area under the receiver operating characteristic (AUROC) curve for models and datasets from the UI cohort was 0.735 and 0.798 for the variant and gene analysis respectively and for the AoU cohort was 0.687 for the variant analysis. Our analysis prioritized several novel and known candidate host genetic factors involved in immune response, neuronal signaling, and calcium signaling supporting previously proposed hypotheses for anosmia/ageusia in COVID-19.

Background: Malignant peripheral nerve sheath tumors (MPNSTs) are deadly sarcomas that arise from Schwann cells and lack effective therapies. RABL6A is an oncogenic Rab-like GTPase whose expression is associated with worse survival in many human cancers. It is required for human MPNST cell survival, and its expression is dramatically increased in patient MPNSTs compared to benign precursor lesions. Methods: To model elevated expression of RABL6A in vivo, we developed transgenic mice expressing Cre-inducible Rabl6a. These Rabl6a-tg mice express the murine Rabl6a cDNA with a 5′ hemagglutinin [HA] epitope sequence downstream of a CMV enhancer and separated by a lox–stop–lox cassette. Double transgenic DhhCre; Rabl6a-tg mice were generated to achieve Schwann-cell specific Cre expression from the Desert hedgehog (Dhh) promoter. De novo MPNSTs were induced by CRISPR editing of Nf1, Ink4a, and Arf genes in the mouse sciatic nerve. Results: Cre-dependent expression of transgenic Rabl6a was verified at the mRNA and protein levels in Cre-positive mouse embryo fibroblasts and tissues. Increased Rabl6a expression in DhhCre; Rabl6a-tg mice had no effect on de novo MPNST initiation but significantly accelerated tumor progression relative to DhhCre control mice. The Rabl6a phenotype was associated with increased tumor angiogenesis but not proliferation. Interestingly, many MPNSTs in the DhhCre background exhibited varying levels of rhabdomyoblastic (RMB) features. That immature muscle cell phenotype is a hallmark of malignant Triton tumors, a rare histological variant of human MPNSTs associated with worse outcomes. Conclusions: These data provide direct evidence that Rabl6a is a functional driver of MPNSTs while establishing Rabl6a-tg mice as a suitable model for investigating Rabl6a’s role in other lethal RABL6A-high tumors.

Supplementary Table S5. Abbreviated list of top kinase inhibitory compounds predicted to be effective against MPNSTs from C-Map analyses of the MPNST transcriptome from NF1 patients.

Supplementary Figure S6. Analysis of helper (CD4) and pan (CD3) T cells in combination therapysensitive versus combination therapy-resistant MPNSTs

Supplementary Table S4. Primers for qRT-PCR analyses

Supplementary Figure S5. Evaluation of differentially expressed genes (DEGs) and tumor infiltrating immune cells (plasma cells and B cells) in drug-treated de novo MPNSTs.

Supplementary Table S3. Cluster of differentiation (CD) markers used to delineate immune cell populations after gating on CD45+ live cells.

Supplementary Table S1. Antibody sources and conditions for western blotting, IF, and IHC

Supplementary Figure S7. Analyses of p-RB1, Ki67, and PD-L1 in combination therapy-sensitive and - resistant MPNSTs and PD-L1 in NF1 patient tumors.