Expression profiling of attenuated mitochondrial function identifies retrograde signals in Drosophila.
Mitochondria are able to modulate cell state and fate during normal and pathophysiologic conditions through a nuclear-mediated mechanism collectively termed as a retrograde response. Our previous studies in Drosophila melanogaster have clearly established that progress through the cell cycle is precisely regulated by the intrinsic activity of the mitochondrion by specific signaling cascades mounted by the cell. As a means to further our understanding of how mitochondrial energy status affects nuclear control of basic cell decisions, we have employed Affymetrix microarray-based transcriptional profiling of Drosophila S2 cells knocked down for the gene encoding subunit Va of the complex IV of the mitochondrial electron transport chain. The profiling data identify transcriptional upregulation of glycolytic genes, and metabolic studies confirm this increase in glycolysis. The data provide a model of the shift of metabolism from a predominately oxidative state toward a predominately aerobic glycolytic state mediated through transcriptional control. The transcriptional changes alter many signaling systems, including p53, insulin, hypoxia-induced factor α, and conserved mitochondrial retrograde responses. This rich dataset provides many novel targets for further understanding the mechanism whereby the mitochondrion manages energy substrate disposition and directs cellular fate decisions.
Vaults are cytoplasmic ribonucleoprotein structures that display a complex morphology reminiscent of the multiple arches which form cathedral vaults, hence their name. Previous studies on rat liver vaults (Kedersha, N. L., and L. H. Rome. 1986. J. Cell Biol. 103:699-709) have established that their composition is unlike that of any known class of RNA-containing particles in that they contain multiple copies of a unique small RNA and more than 50 copies of a single polypeptide of 104,000 Mr. We now report on the isolation of vaults from numerous species and show that vaults appear to be ubiquitous among eukaryotes, including mammals, amphibians (Rana catesbeiana and Xenopus laevis), avians (Gallus Gallus), and the lower eukaryote Dictyostelium discoideum. Electron microscopy reveals that vaults purified from these diverse species are similar both in their dimensions and morphology. The vaults from these various species are also similar in their polypeptide composition; each being composed of a major polypeptide with an approximate mass of 100 kD and several minor polypeptides with molecular masses similar to those seen in the rat. Antibodies raised against rat vaults recognize the major vault protein of all species including Dictyostelium. Vaults therefore appear to be strongly conserved and broadly distributed, suggesting that their function is essential to eukaryotic cells.
Naive and primed pluripotent human embryonic stem cells bear transcriptional similarity to pre- and post-implantation epiblast and thus constitute a developmental model for understanding the pluripotent stages in human embryo development. To identify new transcription factors that differentially regulate the unique pluripotent stages, we mapped open chromatin using ATAC-seq and found enrichment of the activator protein-2 (AP2) transcription factor binding motif at naive-specific open chromatin. We determined that the AP2 family member TFAP2C is upregulated during primed to naive reversion and becomes widespread at naive-specific enhancers. TFAP2C functions to maintain pluripotency and repress neuroectodermal differentiation during the transition from primed to naive by facilitating the opening of enhancers proximal to pluripotency factors. Additionally, we identify a previously undiscovered naive-specific POU5F1 (OCT4) enhancer enriched for TFAP2C binding. Taken together, TFAP2C establishes and maintains naive human pluripotency and regulates OCT4 expression by mechanisms that are distinct from mouse.
Multiple experiments using diabetes animal models have demonstrated the antihyperglycemic properties of several Mexican Copalchi species, mainly Hintonia latiflora (HLA) and Hintonia standleyana (HSL). The active compounds of these plants have recently been characterized and their therapeutic mechanisms proposed. Though widely studied in animals, evidence indicating therapeutic efficacy in patients with non-insulin-dependent diabetes mellitus (NIDDM) is limited. Still, copalchis have been utilized as a folk remedy, and in Germany as a marketed drug, for managing NIDDM. The risks and benefits of using this drug warrant critical analysis. This review summarizes research evidence for the antidiabetic efficacy of Copalchis in NIDDM animal models, recent toxicity findings, and limited clinical findings in human subjects.