ERAD components Derlin-1 and Derlin-2 are essential for postnatal brain development and motor function

Derlin family members (Derlins) are primarily known as components of the endoplasmic reticulum-associated degradation pathway that eliminates misfolded proteins. Here we report a function of Derlins in the brain development. Deletion of Derlin-1 or Derlin-2 in the central nervous system of mice impaired postnatal brain development, particularly of the cerebellum and striatum, and induced motor control deficits. Derlin-1 or Derlin-2 deficiency reduced neurite outgrowth in vitro and in vivo and surprisingly also inhibited sterol regulatory element binding protein 2 (SREBP-2)-mediated brain cholesterol biosynthesis. In addition, reduced neurite outgrowth due to Derlin-1 deficiency was rescued by SREBP-2 pathway activation. Overall, our findings demonstrate that Derlins sustain brain cholesterol biosynthesis, which is essential for appropriate postnatal brain development and function

Epigenetic regulation of neural stem cell property from embryo to adult

Neural stem cells (NSCs) have the ability to self-renew and give rise to neurons and glial cells (astrocytes and oligodendrocytes) in the mammalian central nervous system. This multipotency is acquired by NSCs during development and is maintained throughout life. Proliferation, fate specification, and maturation of NSCs are regulated by both cell intrinsic and extrinsic factors. Epigenetic modification is a representative intrinsic factor, being involved in many biological aspects of central nervous system development and adult neurogenesis through the regulation of NSC dynamics. In this review, we summarize recent progress in the epigenetic regulation of NSC behavior in the embryonic and adult brain, with particular reference to DNA methylation, histone modification, and noncoding RNAs

Introducing Assignment Functions to Bayesian Optimization Algorithms

In this paper we improve Bayesian optimization algorithms by introducing proportionate and rank-based assignment functions. A Bayesian optimization algorithm builds a Bayesian network from a selected sub-population of promising solutions, and this probabilistic model is employed to generate the offspring of the next generation. Our method assigns each solution a relative significance based on its fitness, and this information is used in building the Bayesian network model. These assignment functions can improve the quality of the model without performing an explicit selection on the population. Numerical experiments demonstrate the effectiveness of this method compared to a conventional BOA. Key words: evolutionary computation, Bayesian optimization algorithms, assignment functions

Effect of fenofibrate and selective PPARα modulator (SPPARMα), pemafibrate on KATP channel activity and insulin secretion

Abstract Objective Insulin secretion is regulated by ATP-sensitive potassium (KATP) channels in pancreatic beta-cells. Peroxisome proliferator-activated receptors (PPAR) α ligands are clinically used to treat dyslipidemia. A PPARα ligand, fenofibrate, and PPARγ ligands troglitazone and 15-deoxy-∆12,14-prostaglandin J2 are known to close KATP channels and induce insulin secretion. The recently developed PPARα ligand, pemafibrate, became a new entry for treating dyslipidemia. Because pemafibrate is reported to improve glucose intolerance in mice treated with a high fat diet and a novel selective PPARα modulator, it may affect KATP channels or insulin secretion. Results The effect of fenofibrate (100 µM) and pemafibrate (100 µM) on insulin secretion from MIN6 cells was measured by using batch incubation for 10 and 60 min in low (2 mM) and high (10 mM) glucose conditions. The application of fenofibrate for 10 min significantly increased insulin secretion in low glucose conditions. Pemafibrate failed to increase insulin secretion in all of the conditions experimented in this study. The KATP channel activity was measured by using whole-cell patch clamp technique. Although fenofibrate (100 µM) reduced the KATP channel current, the same concentration of pemafibrate had no effect. Both fenofibrate and pemafibrate had no effect on insulin mRNA expression

Essential roles of aspartate aminotransferase 1 and vesicular glutamate transporters in β-cell glutamate signaling for incretin-induced insulin secretion

<div><p>Incretins (GLP-1 and GIP) potentiate insulin secretion through cAMP signaling in pancreatic β-cells in a glucose-dependent manner. We recently proposed a mechanistic model of incretin-induced insulin secretion (IIIS) that requires two critical processes: 1) generation of cytosolic glutamate through the malate-aspartate (MA) shuttle in glucose metabolism and 2) glutamate transport into insulin granules by cAMP signaling to promote insulin granule exocytosis. To directly prove the model, we have established and characterized CRISPR/Cas9-engineered clonal mouse β-cell lines deficient for the genes critical in these two processes: aspartate aminotransferase 1 (AST1, gene symbol <i>Got1</i>), a key enzyme in the MA shuttle, which generates cytosolic glutamate, and the vesicular glutamate transporters (VGLUT1, VGLUT2, and VGLUT3, gene symbol <i>Slc17a7</i>, <i>Slc17a6</i>, and <i>Slc17a8</i>, respectively), which participate in glutamate transport into secretory vesicles. <i>Got1</i> knockout (KO) β-cell lines were defective in cytosolic glutamate production from glucose and showed impaired IIIS. Unexpectedly, different from the previous finding that global <i>Slc17a7</i> KO mice exhibited impaired IIIS from pancreatic islets, β-cell specific <i>Slc17a7</i> KO mice showed no significant impairment in IIIS, as assessed by pancreas perfusion experiment. Single <i>Slc17a7</i> KO β-cell lines also retained IIIS, probably due to compensatory upregulation of <i>Slc17a6</i>. Interestingly, triple KO of <i>Slc17a7</i>, <i>Slc17a6</i>, and <i>Slc17a8</i> diminished IIIS, which was rescued by exogenously introduced wild-type <i>Slc17a7</i> or <i>Slc17a6</i> genes. The present study provides direct evidence for the essential roles of AST1 and VGLUTs in β-cell glutamate signaling for IIIS and also shows the usefulness of the CRISPR/Cas9 system for studying β-cells by simultaneous disruption of multiple genes.</p></div

Immunofluorescence staining of <i>Slc17a7</i> single KO and <i>Slc17a7</i>, <i>Slc17a6</i>, and <i>Slc17a8</i> triple KO β-cell lines.

<p>Green, Insulin; red, VGLUT1 (A) or VGLUT2 (B); blue, 4',6-diamidino-2-phenylindole (DAPI). Scale bars, 50 μm.</p

Characterization of <i>Slc17a7</i>, <i>Slc17a6</i>, and <i>Slc17a8</i> triple KO β-cell lines.

<p>(A) Insulin secretory response in <i>Slc17a7</i>, <i>Slc17a6</i>, and <i>Slc17a8</i> triple KO (TKO) cell lines. WT and TKO cell lines were stimulated with glucose and incretin (GLP-1 or GIP) (n = 4). Insulin secretion was normalized by cellular insulin content and the data are presented as fold-change relative to the amount of insulin secretion at 16.7 mM glucose. (B, C) Rescue of the VGLUT1 (B) or VGLUT2 (C) activity by introducing WT <i>Slc17a7</i> or <i>Slc17a6</i> into triple KO cell line, respectively. The cell line V39 was transfected with <i>INS1</i> (control) or <i>INS1</i> and rescue construct and stimulated with glucose and GLP-1 (n = 4). C-peptide secretion was normalized by cellular C-peptide content and the data are presented as fold-change relative to the amount of C-peptide secretion at 16.7 mM glucose. (D) The effect of dimethyl glutamate (dmGlu) on insulin secretion. The cell line V39 was stimulated with glucose and dmGlu (n = 4). Insulin secretion was normalized by cellular insulin content. The data are expressed as means ± SEM. Representative results are shown. Similar results were found in 3 independent experiments. Dunnett's method was used for evaluation of statistical significance vs. WT in (A) and vs. 16.7 mM glucose in (D). Welch’s t-test was used for evaluation of statistical significance vs. control in (B) and (C). **p < 0.01; ***p < 0.001.</p