Efecto de la inhibición del sistema de fosforilación oxidativa sobre la diferenciación neuronal en la enfermedad de Alzheimer

La enfermedad de Alzheimer es un síndrome neurodegenerativo progresivo del sistema nervioso central caracterizado principalmente por deterioro cognitivo y pérdida de memoria. De acuerdo a la hipótesis de cascada mitocondrial, se ha propuesto que la causa de esta patología podría ser el declive de la funcionalidad del sistema de fosforilación oxidativa mitocondrial, responsable de la generación de energía en las células e implicado en la diferenciación neuronal. Puesto que este declive puede estar acrecentado por factores ambientales, se ha estudiado el efecto que tiene el cloruro de tributilestaño, un xenobiótico ambiental que inhibe el sistema de fosforilación oxidativa, sobre la diferenciación neuronal. El estudio del efecto de concentraciones inhibitorias de la función mitocondrial de este xenobiótico se ha realizado en células SH-SY5Y, modelos celulares de enfermedad de Alzheimer ampliamente utilizados en investigación, durante procesos de diferenciación a neurona colinérgica y dopaminérgica. Concentraciones crecientes de tributilestaño disminuyen la respiración mitocondrial y parecen ser citotóxicas para la línea celular cuando se encuentra sometida a tratamiento con ácido retinoico, un agente inductor de la diferenciación. El análisis morfológico y del marcador neuronal beta-III-tubulina muestran que la exposición a 50 nM de tributilestaño impide la diferenciación neuronal en todos los casos estudiados, mientras que 25 nM impide únicamente la diferenciación colinérgica

The cohesin acetylation cycle controls chromatin loop length through a PDS5A brake mechanism

Cohesin structures the genome through the formation of chromatin loops and by holding together the sister chromatids. The acetylation of cohesin’s SMC3 subunit is a dynamic process that involves the acetyltransferase ESCO1 and deacetylase HDAC8. Here we show that this cohesin acetylation cycle controls the three-dimensional genome in human cells. ESCO1 restricts the length of chromatin loops, and of architectural stripes emanating from CTCF sites. HDAC8 conversely promotes the extension of such loops and stripes. This role in controlling loop length turns out to be distinct from the canonical role of cohesin acetylation that protects against WAPL-mediated DNA release. We reveal that acetylation controls the interaction of cohesin with PDS5A to restrict chromatin loop length. Our data support a model in which this PDS5A-bound state acts as a brake that enables the pausing and restart of loop enlargement. The cohesin acetylation cycle hereby provides punctuation in the process of genome folding

3D genomics across the tree of life reveals condensin II as a determinant of architecture type

We investigated genome folding across the eukaryotic tree of life. We find two types of three-dimensional(3D) genome architectures at the chromosome scale. Each type appears and disappears repeatedlyduring eukaryotic evolution. The type of genome architecture that an organism exhibits correlates with theabsence of condensin II subunits. Moreover, condensin II depletion converts the architecture of thehuman genome to a state resembling that seen in organisms such as fungi or mosquitoes. In this state,centromeres cluster together at nucleoli, and heterochromatin domains merge. We propose a physicalmodel in which lengthwise compaction of chromosomes by condensin II during mitosis determineschromosome-scale genome architecture, with effects that are retained during the subsequent interphase.This mechanism likely has been conserved since the last common ancestor of all eukaryotes.C.H. is supported by the Boehringer Ingelheim Fonds; C.H., Á.S.C., and B.D.R. are supported by an ERC CoG (772471, “CohesinLooping”); A.M.O.E. and B.D.R. are supported by the Dutch Research Council (NWO-Echo); and J.A.R. and R.H.M. are supported by the Dutch Cancer Society (KWF). T.v.S. and B.v.S. are supported by NIH Common Fund “4D Nucleome” Program grant U54DK107965. H.T. and E.d.W. are supported by an ERC StG (637597, “HAP-PHEN”). J.A.R., T.v.S., H.T., R.H.M., B.v.S., and E.d.W. are part of the Oncode Institute, which is partly financed by the Dutch Cancer Society. Work at the Center for Theoretical Biological Physics is sponsored by the NSF (grants PHY-2019745 and CHE-1614101) and by the Welch Foundation (grant C-1792). V.G.C. is funded by FAPESP (São Paulo State Research Foundation and Higher Education Personnel) grants 2016/13998-8 and 2017/09662-7. J.N.O. is a CPRIT Scholar in Cancer Research. E.L.A. was supported by an NSF Physics Frontiers Center Award (PHY-2019745), the Welch Foundation (Q-1866), a USDA Agriculture and Food Research Initiative grant (2017-05741), the Behavioral Plasticity Research Institute (NSF DBI-2021795), and an NIH Encyclopedia of DNA Elements Mapping Center Award (UM1HG009375). Hi-C data for the 24 species were created by the DNA Zoo Consortium (www.dnazoo.org). DNA Zoo is supported by Illumina, Inc.; IBM; and the Pawsey Supercomputing Center. P.K. is supported by the University of Western Australia. L.L.M. was supported by NIH (1R01NS114491) and NSF awards (1557923, 1548121, and 1645219) and the Human Frontiers Science Program (RGP0060/2017). The draft A. californica project was supported by NHGRI. J.L.G.-S. received funding from the ERC (grant agreement no. 740041), the Spanish Ministerio de Economía y Competitividad (grant no. BFU2016-74961-P), and the institutional grant Unidad de Excelencia María de Maeztu (MDM-2016-0687). R.D.K. is supported by NIH grant RO1DK121366. V.H. is supported by NIH grant NIH1P41HD071837. K.M. is supported by a MEXT grant (20H05936). M.C.W. is supported by the NIH grants R01AG045183, R01AT009050, R01AG062257, and DP1DK113644 and by the Welch Foundation. E.F. was supported by NHGR