Citations

Abstract There are no circulating markers exclusive to cell senescence for clinical trials in middle-aged/older adults. In this study we evaluated T-cell expression of tumor suppressor protein p16INK4a and plasma senescence associated secretory proteins (SASP)-factors in the context of an 18-week randomized trial of caloric restriction (CR) compared to a weight stable Control. The analysis includes 55 middle-aged/older adults (75%Women; 33%African American; 57.6±5.8 years) with obesity and prediabetes. We measured mRNA expression of select senescence and apoptosis gene transcripts (p16INK4a, p21, BCL2L, BAK1) in peripheral blood CD3+ T-cells (quantitative-RT-PCR) and a panel of 27 plasma SASP proteins (Luminex/multiplex; ELISA). Weight loss in those randomized to CR was -10.8±0.9 kg compared to +0.5±0.9 kg in Control. Using mixed models, T-cell expression of senescence-biomarkers p16INK4a, p21, BCL-2L, and apoptosis-marker BAK1 were not different between CR and control at 18 weeks (time × treatment adjusted for age, race, and sex, all p>0.05). We explored associations between biomarkers with weight loss; moderate spearman correlations (rs=0.28 to 0.64) were observed between weight loss and change in plasma SASP-factors (Activin A, I-CAM, MMP1, PAI-1, TNF-RI, TNF-RII, VEGF, uPAR, p< 0.05 all), but not T-cell biomarker expression. We evaluated associations between biomarkers and found change in T-cell p16INK4a was associated with change in plasma SASP-factors, Fas (rs=0.51), osteopontin (rs=0.34), myeloperoxidase (rs=0.39), and MMP2 (rs=0.40) (CR+Control combined). Among middle-aged/older persons with obesity undergoing 18-weeks CR, changes in T cell p16INK4a expression were correlated with reductions in key SASP factors, and weight loss was associated with lower pro-inflammatory SASP profile.

AbstractBackgroundApolipoprotein E (APOE) and clusterin (CLU) are critical in the pathogenesis of Alzheimer’s disease (AD). Common coding variants in APOE (e.g. APOE4) impart at least 3‐fold higher risk of developing AD, while common noncoding variants in CLU impart smaller but still highly significant risk for AD. Using genetically engineered mouse models lacking either APOE or CLU, previous studies from our lab and others have shown that both are critical in the formation of amyloid. However, only a single published study has examined the combined effects of APOE and CLU in a mouse model of amyloidosis.MethodsWe generated mice that lacked both murine APOE and CLU (double knockout mice) on the APP/PS1 background of AD amyloidosis. We assessed these mice using histological analysis as well as single‐cell RNAseq profiling from brain tissue.ResultsCompared to APP/PS1 controls, we found that double knockout mice for both APOE and CLU had a striking reduction in the amount of amyloid plaques in the cortex. Moreover, we found that these double‐knockout mice were completely void of amyloid plaques in the hippocampus. Single‐cell RNAseq experiments revealed a strong reduction in the amount of activated microglia in these double knockout mice.ConclusionsContrary to a previous study that reported increased amyloid load in APOE‐/‐;CLU‐/‐ double knockout mice, we found a dramatic reduction in amyloid plaques and a concomitant loss of activated microglia when using genetically inbred (C57BL/6J) mouse lines. Further studies are needed to determine whether these effects are cell‐type specific (e.g. astrocyte‐derived APOE and CLU conditional knockouts) or whether these lipoproteins have synergistic roles in tau pathology.

Cross-talk between Rho- and Arf-family guanosine triphosphatases (GTPases) plays an important role in linking the actin cytoskeleton to membrane protrusions, organelle morphology, and vesicle trafficking. The central actin regulator, WAVE regulatory complex (WRC), integrates Rac1 (a Rho-family GTPase) and Arf signaling to promote Arp2/3-mediated actin polymerization in many processes, but how WRC senses Arf signaling is unknown. Here, we have reconstituted a direct interaction between Arf and WRC. This interaction is greatly enhanced by Rac1 binding to the D site of WRC. Arf1 binds to a previously unidentified, conserved surface on the Sra1 subunit of WRC, which, in turn, drives WRC activation using a mechanism distinct from that of Rac1. Mutating the Arf binding site abolishes Arf1-WRC interaction, disrupts Arf1-mediated WRC activation, and impairs lamellipodia formation and cell migration. This work uncovers a new mechanism underlying WRC activation and provides a mechanistic foundation for studying how WRC-mediated actin polymerization links Arf and Rac signaling in cells.

The clinical and largely unpredictable heterogeneity of phenotypes in patients with mitochondrial disorders demonstrates the ongoing challenges in the understanding of this semi-autonomous organelle in biology and disease. Previously, we used the gene-breaking transposon to create 1200 transgenic zebrafish strains tagging protein-coding genes (Ichino et al., 2020), including the lrpprc locus. Here, we present and characterize a new genetic revertible animal model that recapitulates components of Leigh Syndrome French Canadian Type (LSFC), a mitochondrial disorder that includes diagnostic liver dysfunction. LSFC is caused by allelic variations in the LRPPRC gene, involved in mitochondrial mRNA polyadenylation and translation. lrpprc zebrafish homozygous mutants displayed biochemical and mitochondrial phenotypes similar to clinical manifestations observed in patients, including dysfunction in lipid homeostasis. We were able to rescue these phenotypes in the disease model using a liver-specific genetic model therapy, functionally demonstrating a previously under-recognized critical role for the liver in the pathophysiology of this disease.