Remodelación alterada de la cromatina y cambios en la expresión de genes en astrocitos de esclerosis lateral amiotrófica
Cargando...
Archivos
Fecha
2019
Profesor/a Guía
Facultad/escuela
Idioma
es
Título de la revista
ISSN de la revista
Título del volumen
Editor
Universidad Andrés Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
La esclerosis lateral amiotrófica (ELA) es una enfermedad neurodegenerativa letal que se manifiesta por la pérdida selectiva y progresiva de las motoneuronas. Ha sido reportado que astrocitos de ratón que sobre expresan laSOD1 humana con la mutación G93A (mutSOD1), desencadenan la muerte específica de las motoneuronas. Además, estos astrocitos presentan un aumento global en la transcripción comparado con su control. No se conocen los mecanismos que alteran la regulación transcripcional de los astrocitos mutSOD1. Se ha demostrado que la transcripción en eucariontes es regulada por la cromatina, una estructura especializada que permite empaquetar el “DNA”, protegerlo del daño y regular la actividad de los genes. Específicamente, la marca de histona H3K9me3 permite mediar niveles de empaquetamiento superior de la cromatina. Está reportado que una disminución de marcas represoras,comoH3K9me3,genera pérdida de la estructura de heterocromatina y aumentos a nivel transcripcional, por lo que su mantenimiento es crucial en la regulación del genoma. Por lo tanto, en esta tesis proponemos la siguiente hipótesis: en astrocitos mutSOD1 existe una desorganización de la cromatina, reflejada en una pérdida o redistribución de nucleosomas en regiones que disminuyen la marca H3K9me3, generándose un aumento transcripcional en estos segmentos genómicos. Utilizando una serie de técnicas de secuenciación, “ATAC-seq”, “RNA-seq”y “ChIP-seq”,encontramos que: 1) en astrocitos mutSOD1 se observan masivas alteraciones en la expresión de genes comparado con el wtSOD1, que interesantemente, se asocian a genes específicos de tejidos no relacionados con el SNC, los cuales están aumentados en astrocitosmutSOD1, sugiriendo una trans diferenciación celular; 2) Al analizar la cromatina, encontramos cambios en la distribución delos nucleosomas en regiones no codificantes como LINEs, SINEs y LTRs; y 3) encontramos que la pérdida de la marcaH3K9me3 también ocurre en elementos transponibles, principalmente en las regiones no codificantes SINEs y LTRs. Esto sugiere que la pérdida deH3K9me3 puede generar inestabilidad genómica en astrocitos mutSOD1.
Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease manifested by the selective and progressive loss of motoneurons. It has been reported that mouse astrocytes over-expressing human SOD1 with the G93A mutation (mutSOD1), trigger the specific death of motoneurons. In addition, these astrocytes present an overall increase in transcription compared to WT astrocyte. The mechanisms that alter the transcriptional regulation of astrocytes mutSOD1 are not known. It has been shown that transcription in eukaryotes is regulated by chromatin, a specialized structure that makes it possible to package the DNA, protect it from damage and regulate the activity of the genes. Specifically, the histone mark H3K9me3whichallows to mediate superior packaging levels of chromatin. It is reported that a decrease in repressor marks, such as H3K9me3, generates loss of the heterochromatin structure and increases at the transcriptional level, so itis maintenance is crucial in the regulation of the genome. Therefore, in this thesis we propose the following hypotheses: in astrocytes mutSOD1 there is a disorganization of the chromatin, reflected in a loss or redistribution of nucleosomes in regions that reduce the H3K9me3 mark, generating a transcriptional increase in these genomic segments. Using a series of sequencing techniques, ATAC-seq, RNA-seq and ChIP-seq, we found that: 1) in mutSOD1 astrocytes, massive alterations in gene expression are observed compared to wtSOD1, which, interestingly, are associated with tissue-specific genes unrelated with the CNS, which are increased in mutSOD1 astrocytes, suggesting cellular transdifferentiation; 2) When analyzing chromatin, we find changes in the distribution of nucleosomes in non-coding regions such as LINEs, SINEs and LTRs; and 3) we found that the loss of the H3K9me3 mark also occurs in transposable elements, mainly in the non-coding regions SINEs and LTRs. This suggests that the loss of H3K9me3 can generate genomic instability in mutSOD1 astrocytes.
Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease manifested by the selective and progressive loss of motoneurons. It has been reported that mouse astrocytes over-expressing human SOD1 with the G93A mutation (mutSOD1), trigger the specific death of motoneurons. In addition, these astrocytes present an overall increase in transcription compared to WT astrocyte. The mechanisms that alter the transcriptional regulation of astrocytes mutSOD1 are not known. It has been shown that transcription in eukaryotes is regulated by chromatin, a specialized structure that makes it possible to package the DNA, protect it from damage and regulate the activity of the genes. Specifically, the histone mark H3K9me3whichallows to mediate superior packaging levels of chromatin. It is reported that a decrease in repressor marks, such as H3K9me3, generates loss of the heterochromatin structure and increases at the transcriptional level, so itis maintenance is crucial in the regulation of the genome. Therefore, in this thesis we propose the following hypotheses: in astrocytes mutSOD1 there is a disorganization of the chromatin, reflected in a loss or redistribution of nucleosomes in regions that reduce the H3K9me3 mark, generating a transcriptional increase in these genomic segments. Using a series of sequencing techniques, ATAC-seq, RNA-seq and ChIP-seq, we found that: 1) in mutSOD1 astrocytes, massive alterations in gene expression are observed compared to wtSOD1, which, interestingly, are associated with tissue-specific genes unrelated with the CNS, which are increased in mutSOD1 astrocytes, suggesting cellular transdifferentiation; 2) When analyzing chromatin, we find changes in the distribution of nucleosomes in non-coding regions such as LINEs, SINEs and LTRs; and 3) we found that the loss of the H3K9me3 mark also occurs in transposable elements, mainly in the non-coding regions SINEs and LTRs. This suggests that the loss of H3K9me3 can generate genomic instability in mutSOD1 astrocytes.
Notas
Tesis (Doctor en Biociencias Moleculares)
Palabras clave
Enzimas, Esclerosis Lateral Amiotrófica