Project description:The dynamin-like GTPases Mitofusin 1 and 2 (Mfn1 and Mfn2) are essential for mitochondrial function, which has been principally attributed to their regulation of fission/fusion dynamics. Here, we report that Mfn1 and 2 are critical for glucose-stimulated insulin secretion (GSIS) primarily through control of mtDNA content. Whereas Mfn1 and Mfn2 individually were dispensable for glucose homeostasis, combined Mfn1/2 deletion in β-cells reduced mtDNA content, induced impaired mitochondrial morphology and networking fragmentation, and impaired decreased respiratory function, ultimately resulting in severe glucose intolerance. Importantly, gene dosage studies unexpectedly revealed that Mfn1/2 control of glucose homeostasis was dependent on maintenance of mtDNA content, rather than mitochondrial structure. Indeed, pharmacologic mitofusin agonists rescued islet mtDNA depletion due to mitofusin deficiency independent of changes on mitochondrial structure. Mfn1/2 maintain mtDNA content by regulating the expression of the crucial mitochondrial transcription factor Tfam, as Tfam overexpression ameliorated the reduction in mtDNA content and GSIS in Mfn1/2-deficient β-cells. Thus, the primary physiologic role of Mfn1 and 2 in β-cells is coupled to preservation of mtDNA content rather than mitochondrial architecture, and Mfn1 and 2 may be promising targets to overcome mitochondrial dysfunction and restore glucose control in diabetes.
Project description:Mouse tibialis anterior muscles were electroporated with Nr2f6-myc plasmid or pCMV6 empty vector in the contralateral leg. After 9 days, muscles were collected, and the RNA extracted and processed for microarray analysis.
Project description:Objective: A biallelic missense mutation in mitofusin 2 (MFN2) causes multiple symmetric lipomatosis and partial lipodystrophy, implicating disruption of mitochondrial fusion or interaction with other organelles in adipocyte differentiation, growth and/or survival. In this study, we aimed to document the impact of loss of mitofusin 1 (Mfn1) or 2 (Mfn2) on adipogenesis in cultured cells. Methods: We characterised adipocyte differentiation of wildtype (WT), Mfn1-/- and Mfn2-/- mouse embryonic fibroblasts (MEFs) and 3T3-L1 preadipocytes in which Mfn1 or 2 levels were reduced using siRNA. Results: Mfn1-/- MEFs displayed striking fragmentation of the mitochondrial network, with surprisingly enhanced propensity to differentiate into adipocytes, as assessed by lipid accumulation, expression of adipocyte markers (Plin1, Fabp4, Glut4, Adipoq), and insulin-stimulated glucose uptake. RNA sequencing revealed a corresponding pro-adipogenic transcriptional profile including Pparg upregulation. Mfn2-/- MEFs also had a disrupted mitochondrial morphology, but in contrast to Mfn1-/- MEFs they showed reduced expression of adipocyte markers. Mfn1 and Mfn2 siRNA mediated knockdown studies in 3T3-L1 adipocytes generally replicated these findings. Conclusions: Loss of Mfn1 but not Mfn2 in cultured pre-adipocyte models is pro-adipogenic. This suggests distinct, non-redundant roles for the two mitofusin orthologues in adipocyte differentiation.
Project description:We generated transgenic mice expressing constitutively SOCS-3 specifically in skeletal muscle. SOCS proteins are implicated in the negative regulation of various pathways including insulin signaling pathway. Our transgenic mice are predisposed to obesity and systemic insulin resistance compared to control mice. We used microarrays to detail the variations of gene expression in muscle from transgenic mice versus controls. Keywords: transgenic, tibialis anterior, SOCS-3
Project description:Proteomic study of tibialis anterior muscle harvested at 1 day and 7 days post-injection with novel polyurethane nanoparticles compared to water sham and non-injected controls
Project description:Transcription profiling of skeletal muscle (tibialis anterior) of 5-week-old male wild type and myostatin null mice given ad libitum access to 20ppm clenbuterol hydrochloride in drinking water or plain tap water for 2 weeks. The objective of the study was to determine overlap in the mechanisms of muscle hypertrophy of the two models.
Project description:Genome-wide gene expression analysis on tibialis anterior muscle from 2-month-old nebulin SH3 domain deleted (Neb∆SH3) mice compared to wildtype. Total RNA was obtained from biological triplicates of tibialis anterior muscle from 2-month-old nebulin SH3 domain deleted (Neb∆SH3) mice compared to wildtype.
