Nicotinamide adenine dinucleotide (NAD)؉ -dependent sirtuins have been identified to be key regulators in the lifespan extending effects of calorie restriction (CR) in a number of species. In this study we report for the first time that promotion of the NAD ؉ -dependent sirtuin, SIRT1-mediated deacetylase activity, may be a mechanism by which CR influences Alzheimer disease (AD)-type amyloid neuropathology. Most importantly, we report that the predicted attenuation of ␤-amyloid content in the brain during CR can be reproduced in mouse neurons in vitro by manipulating cellular SIRT1 expression/activity through mechanisms involving the regulation of the serine/threonine Rho kinase ROCK1, known in part for its role in the inhibition of the non-amyloidogenic ␣-secretase processing of the amyloid precursor protein. Conversely, we found that the expression of constitutively active ROCK1 in vitro cultures significantly prevented SIRT1-mediated response, suggesting that ␣-secretase activity is required for SIRT1-mediated prevention of AD-type amyloid neuropathology. Consistently we found that the expression of exogenous human (h) SIRT1 in the brain of hSIRT1 transgenics also resulted in decreased ROCK1 expression and elevated ␣-secretase activity in vivo. These results demonstrate for the first time a role for SIRT1 activation in the brain as a novel mechanism through which CR may influence AD amyloid neuropathology. The study provides a potentially novel pharmacological strategy for AD prevention and/or treatment.Sirtuins are a family of NAD ϩ -dependent histone/protein deacetylases that are highly conserved in their catalytic domains and are distributed across all kingdoms of life (1-4). These enzymes utilize NAD ϩ as a substrate to catalyze deacetylation of specific acetylated-protein substrates (1, 5). Sirtuins can deacetylate a variety of substrates and are, therefore, involved in a broad range of physiological functions, including control of gene expression, metabolism, and aging (6). Accumulating evidence implicates sirtuins in calorie restriction (CR)-mediated health effects including increased organism longevity in yeast, worms, flies, and mammals (1-4, 6). Mammalian genomes encode seven distinct sirtuins (SIRT1-SIRT7). SIRT1 is induced by CR 4 in several tissues and has been implicated in various effects such as stress resistance, reduced apoptosis, and metabolic changes associated with CR (1). SIRT1 is also expressed in the developing and the adult mammalian brain (7). Based on these considerations and on the evidence that CR prevents AD-type amyloid neuropathology in animal models (8, 9), we sought to test the hypothesis that CR may reduce AD-type amyloid neuropathology through mechanisms involving promotion of SIRT1. The relevance of CR treatment in experimental models of AD to human pathology is supported by recent epidemiological evidence suggesting that humans who maintain a low calorie diet have a reduced risk of developing AD (10 -12).Abnormal A␤ deposition within the brain is a hallmark of AD neuropat...

Left ventricular noncompaction (LVNC) causes prominent ventricular trabeculations and reduces cardiac systolic function. The clinical presentation of LVNC ranges from asymptomatic to heart failure. We show that germline mutations in human MIB1 (mindbomb homolog 1), which encodes an E3 ubiquitin ligase that promotes endocytosis of the NOTCH ligands DELTA and JAGGED, cause LVNC in autosomal-dominant pedigrees, with affected individuals showing reduced NOTCH1 activity and reduced expression of target genes. Functional studies in cells and zebrafish embryos and in silico modeling indicate that MIB1 functions as a dimer, which is disrupted by the human mutations. Targeted inactivation of Mib1 in mouse myocardium causes LVNC, a phenotype mimicked by inactivation of myocardial Jagged1 or endocardial Notch1. Myocardial Mib1 mutants show reduced ventricular Notch1 activity, expansion of compact myocardium to proliferative, immature trabeculae and abnormal expression of cardiac development and disease genes. These results implicate NOTCH signaling in LVNC and indicate that MIB1 mutations arrest chamber myocardium development, preventing trabecular maturation and compaction.

Lethal 3 malignant brain tumor 1 (L3MBTL1), a homolog of the Drosophila polycomb tumor suppressor l(3)mbt, contains three tandem MBT repeats (3xMBT) that are critical for transcriptional repression. We recently reported that the 3xMBT repeats interact with mono-and dimethylated lysines in the amino termini of histones H4 and H1b to promote methylation-dependent chromatin compaction. Using a series of histone peptides, we now show that the recognition of mono-and dimethylated lysines in histones H3, H4 and H1.4 (but not their trimethylated or unmodified counterparts) by 3xMBT occurs in the context of a basic environment, requiring a conserved aspartic acid (D355) in the second MBT repeat. Despite the broad range of in vitro binding, the chromatin association of L3MBTL1 mirrors the progressive accumulation of H4K20 monomethylation during the cell cycle. Furthermore, transcriptional repression by L3MBTL1 is enhanced by the H4K20 monomethyltransferase PR-SET7 (to which it binds) but not SUV420H1 (an H4K20 trimethylase) or G9a (an H3K9 dimethylase) and knockdown of PR-SET7 decreases H4K20me1 levels and the chromatin association of L3MBTL1. Our studies identify the importance of H4K20 monomethylation and of PR-SET7 for L3MBTL1 function.

He has been at CNIC since 2009. His research interest focuses on cardiac valves development and disease. -Juliane Münch is a postdoctoral researcher at Potsdam University and the BSRT at Charité, Berlin, Germany. She made her PhD at CNIC in Madrid, Spain, studying the role of Notch signalling in zebrafish fin and heart regeneration. Her current research focuses on the specification of endocardial progenitors during early zebrafish development. -José Luis de la Pompa is senior investigator at CNIC. He made his PhD in Drosophila developmental genetics at CSIC (Spain), postdoctoral in chicken development (EMBL, Germany) and mouse developmental genetics (Ontario Cancer Institute, Canada). CSIC investigator since 2003 and CNIC full professor and senior investigator since 2009. His research centers in the role of cell signalling in cardiac development and disease, and the genetics of CHD.