Project description:Purpose: The goals of this study are to compare next generation sequencing-derived brain cortex transcriptome profiling (RNA-seq) to study the role of neutral sphingomyelinase 2 (smpd3) in brain aging. Methods: Brain cortex mRNA profiles of 10 month old (fro/+) and smpd3 total knockout (fro/fro) mice were generated by deep sequencing, in duplicate, using Illumina NovaSeq 6000. (https://en.novogene.com) Results:A total of 1462 transcripts differed between genotypes, with 891 transcripts increased and 571 transcripts decreased. Conclusions: Transcriptome differences link decreased oxidative stress and astrocyte activation in brain cortex to nSMase2 deficiency, while synaptic signaling transcripts increased in ways consistent with increased cognitive function previously demonstrated in nSMase2-deficient mice.
Project description:Several neurodevelopmental processes including neuronal survival, migration and differentiation are controlled by sphingolipid metabolism. Sphingomyelin is an abundant component of cell membranes. Sphingomyelinases generate ceramide from sphingomyelin as a second messenger in intracellular signaling pathways involved in cell proliferation, differentiation, or apoptosis. While the role of acid sphingomyelinase is well established, the role of neutral sphingomyelinases in human neurodevelopment has remained elusive. Twenty-five children from ten unrelated families presented with microcephaly with simplified gyral pattern, cerebellar hypoplasia, severe developmental encephalopathy, congenital arthrogryposis, diabetes mellitus and early fetal/-postnatal demise. All probands tested have biallelic loss of function variants in SMPD4, coding for neutral sphingomyelinase-3 (nSMase-3 / SMPD4). Fibroblasts from affected individuals showed morphologic endoplasmic reticulum (ER) cisternae abnormalities and increased autophagy, consistent with a previously suggested function of SMPD4 in the ER. Overexpression of human Myc-tagged SMPD4 in HEK293T cells showed localization to both the outer nuclear envelope and the ER. Previous studies localized SMPD4 to the outer nuclear membrane. Mass spectrometry of SMPD4-associated proteins detected peptides belonging to nuclear pore complex proteins. After downregulation of SMPD4 by siRNA, delayed cell cycle progression was observed and primary fibrobalsts from affected individuals were more prone to apoptosis than controls. These data are consistent with former studies in HeLa cells showing mitotic abnormalities after siSMPD4 treatment. This study provides a link between sphingolipid membrane homeostasis, cell fate and mitotic decisions indicating novel pathway in the pathogenesis of microcephaly.
Project description:Ceramides generated by the activity of the neutral sphingomyelinase 2 (NSM2) play a pivotal role in stress responses in mammalian cells. Dysregulation of sphingolipid metabolism has been implicated in numerous inflammation-related pathologies. However, its influence on inflammatory cytokine-induced signaling is yet incompletely understood. Here, we used proximity labeling to explore the plasma membrane proximal protein network of NSM2 and TNFα-induced changes thereof. We established Jurkat cells stably expressing NSM2 C-terminally fused to the engineered ascorbate peroxidase 2 (APEX2). Removal of excess biotin phenol substantially improved streptavidin-based affinity purification of biotinylated proteins. Using our optimized protocol, we determined NSM2-proximal biotinylated proteins and their changes within the first 5 min of TNFα stimulation by quantitative mass spectrometry. We observed significant dynamic changes in the NSM2 microenvironment in response to TNFαstimulation consistent with rapid remodeling of protein networks. Our data confirmed known NSM2 interactors and revealed that the recruitment of most proteins depended on NSM2 enzymatic activity. We measured significant enrichment of proteins related to vesicle-mediated transport, including proteins of recycling endosomes, trans-Golgi network, and exocytic vesicles in the proximitome of enzymatically active NSM2 within the first minutes of TNFα stimulation. Hence, the NSM2 proximal network and its TNFα-induced changes provide a valuable resource for further investigations into the involvement of NSM2 in the early signaling pathways triggered by TNFα.
Project description:The aging brain is highly vulnerable to cellular stress, and neurons often employ numerous mechanisms to combat neurotoxic proteins and promote healthy brain aging. The RNA modification m6A has been shown to be a critical regulator of RNA stability and translation in cells during stress. m6A is highly enriched in the Drosophila brain and is critical for the acute heat stress response. Here we examine m6A response to chronic stresses of aging and degenerative disease. In the brain, m6A levels dynamically increased with age and disease, marking critical signaling pathway transcripts that become downregulated in age and disease. Unexpectedly, there is opposing regulation of m6A transcript translation in neural vs glial cells, which conferred different outcomes on animal healthspan with Mettl3 knockdown to reduce m6A. Moreover, these data reveal that knockdown of Mettl3 in glial tauopathy is beneficial, leading to increased animal survival. These findings provide mechanistic insight into regulation of m6A modified transcripts with age and disease that varies based on cell type.
Project description:MicroRNAs (miRNAs) are endogenous small RNA molecules that regulate gene expression post-transcriptionally. Work in Caenorhabditis elegans has shown that specific miRNAs function in lifespan regulation and in a variety of age-associated pathways, but the roles of miRNAs in the aging of vertebrates are not well understood. We examined the expression of small RNAs in whole brains of young and old mice by deep sequencing and report here on the expression of 233 known miRNAs and identification of 41 novel miRNAs. Of these miRNAs, 75 known and 18 novel miRNAs exhibit greater than 2.0-fold expression changes. The majority of expressed miRNAs in our study decline in relative abundance in the aged brain, in agreement with trends observed in other miRNA studies in aging tissues and organisms. Target prediction analysis suggests that many of our novel aging-associated miRNAs target genes in the insulin signaling pathway, a central node of aging-associated genetic networks. These novel miRNAs may thereby regulate aging-related functions in the brain. Since mouse miRNAs are conserved in humans, the aging-affected brain miRNAs we report here may represent novel regulatory genes that function during aging in the human brain. 2 samples examined: Mouse brain from two young (5 months) and two old animals (24-25 months).
Project description:Acid sphingomyelinase (ASM) inhibitors, which are clinically used as anti-depressants for ~60 years, have recently been shown to enhance stroke recovery in rodents. Using mice and cerebral microvascular endothelial cells exposed to ischemia/reperfusion (I/R) we show that the antidepressants amitriptyline, fluoxetine and desipramine induce angiogenesis in an ASM-dependent way by releasing small extracellular vesicles (sEVs) from endothelial cells, which have bona fide characteristics of exosomes and which, similar to sEVs released during I/R, promote angiogenesis. Post-I/R, ASM inhibition elicits a profound brain remodeling response with increased blood-brain barrier integrity, reduced brain leukocyte infiltrates and increased neuronal survival. The ASM inhibitor-mediated release of sEVs has disclosed an elegant target, via which stroke recovery can be amplified. Key words: Antidepressant, ceramide, exosome, focal cerebral ischemia, middle cerebral artery occlusion, sphingomyelin, stroke recovery