RESUMEN
Maternal malnutrition is one of the major early-life adversities affecting the development of newborn's brain and is associated with an increased risk to acquire cognitive and emotional deficiencies later in life. Studies in rodents have demonstrated that exposure to an enriched environment (EE) can reverse the negative consequences of early adversities. However, rescue of emotional disorders caused by perinatal malnutrition and the mechanisms involved has not been determined. We hypothesized that exposure to an EE may attenuate the anxiety-like disorders observed in mice subjected to perinatal protein malnutrition and that this could be mediated by epigenetic mechanisms. Male CF-1 mice were subject to perinatal protein malnutrition until weaning and then exposed to an EE for 5â¯weeks after which small RNA-seq was performed. In parallel, dark-light box and elevated plus maze tests were conducted to evaluate anxiety traits. We found that exposure to an EE reverses the anxiety-like behavior in malnourished mice. This reversal is paralleled by the expression of three miRNAs that become dysregulated by perinatal malnutrition (miR-187-3p, miR-369-3p and miR-132-3p). The predicted mRNA targets of these miRNAs are mostly related to axon guidance pathway. Accordingly, we also found that perinatal malnutrition leads to reduction in the cingulum size and altered oligodendrocyte morphology. These results suggest that EE-rescue of anxiety disorders derived from perinatal malnutrition is mediated by the modulation of miRNAs associated with the regulation of genes involved in axonal guidance.
Asunto(s)
Ansiedad/metabolismo , Encéfalo/metabolismo , Ambiente , Regulación de la Expresión Génica , Desnutrición/metabolismo , MicroARNs/metabolismo , Oligodendroglía/metabolismo , Animales , Ansiedad/etiología , Ansiedad/patología , Conducta Animal/fisiología , Encéfalo/patología , Forma de la Célula/fisiología , Modelos Animales de Enfermedad , Conducta Exploratoria/fisiología , Vivienda para Animales , Desnutrición/complicaciones , Desnutrición/patología , Ratones , MicroARNs/genética , Oligodendroglía/patologíaRESUMEN
Although important information is available on the molecular mechanisms of long-term memory formation, little is known about the processes underlying memory persistence in the brain. Here, we report that persistent gene expression of CaMKIIδ isoform participates in object recognition long-lasting memory storage in mice hippocampus. We found that CaMKIIδ mRNA expression was sustained up to one week after training and paralleled memory retention. Antisense DNA infusion in the hippocampus during consolidation or even after consolidation impairs 7-day- but not 1-day-long memory, supporting a role of CaMKIIδ in memory persistence. CaMKIIδ gene expression was accompanied by long-lasting nucleosome occupancy changes at its promoter. This epigenetic mechanism is described for the first time in a memory process and offers a novel mechanism for persistent gene expression in neurons. CaMKIIδ protein is mainly present in nucleus and presynaptic terminals, suggesting a role in these subcellular compartments for memory persistence. All these results point to a key function of the sustained gene expression of this overlooked CaMKII isoform in long-lasting memories.
Asunto(s)
Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Hipocampo/metabolismo , Memoria/fisiología , Neuronas/metabolismo , Animales , Miedo/fisiología , Expresión Génica/fisiología , Masculino , Ratones Endogámicos C57BLRESUMEN
Alternative splicing (AS) greatly expands the coding capacities of genomes by allowing the generation of multiple mature mRNAs from a limited number of genes. Although the massive switch in AS profiles that often accompanies variations in gene expression patterns occurring during cell differentiation has been characterized for a variety of models, their causes and mechanisms remain largely unknown. Here, we integrate foundational and recent studies indicating the AS switches that govern the processes of cell fate determination. We include some distinct AS events in pluripotent cells and somatic reprogramming and discuss new progresses on alternative isoform expression in adipogenesis, myogenic differentiation and stimulation of immune cells. Finally, we cover novel insights on AS mechanisms during neuronal differentiation, paying special attention to the role of chromatin structure.
Asunto(s)
Empalme Alternativo , Diferenciación Celular/genética , Animales , HumanosRESUMEN
Alternative splicing, as well as chromatin structure, greatly contributes to specific transcriptional programs that promote neuronal differentiation. The activity of G9a, the enzyme responsible for mono- and di-methylation of lysine 9 on histone H3 (H3K9me1 and H3K9me2) in mammalian euchromatin, has been widely implicated in the differentiation of a variety of cell types and tissues. In a recent work from our group (Fiszbein et al., 2016) we have shown that alternative splicing of G9a regulates its nuclear localization and, therefore, the efficiency of H3K9 methylation, which promotes neuronal differentiation. We discuss here our results in the light of a report from other group (Laurent et al. 2015) demonstrating a key role for the alternative splicing of the histone demethylase LSD1 in controlling specific gene expression in neurons. All together, these results illustrate the importance of alternative splicing in the generation of a proper equilibrium between methylation and demethylation of histones for the regulation of neuron-specific transcriptional programs.
RESUMEN
Chromatin modifications are critical for the establishment and maintenance of differentiation programs. G9a, the enzyme responsible for histone H3 lysine 9 dimethylation in mammalian euchromatin, exists as two isoforms with differential inclusion of exon 10 (E10) through alternative splicing. We find that the G9a methyltransferase is required for differentiation of the mouse neuronal cell line N2a and that E10 inclusion increases during neuronal differentiation of cultured cells, as well as in the developing mouse brain. Although E10 inclusion greatly stimulates overall H3K9me2 levels, it does not affect G9a catalytic activity. Instead, E10 increases G9a nuclear localization. We show that the G9a E10(+) isoform is necessary for neuron differentiation and regulates the alternative splicing pattern of its own pre-mRNA, enhancing E10 inclusion. Overall, our findings indicate that by regulating its own alternative splicing, G9a promotes neuron differentiation and creates a positive feedback loop that reinforces cellular commitment to differentiation.
Asunto(s)
Empalme Alternativo , N-Metiltransferasa de Histona-Lisina/genética , Animales , Azepinas/farmacología , Encéfalo/metabolismo , Diferenciación Celular/efectos de los fármacos , Línea Celular , Núcleo Celular/metabolismo , Exones , Transferencia Resonante de Energía de Fluorescencia , Genes Reporteros , Células HeLa , N-Metiltransferasa de Histona-Lisina/antagonistas & inhibidores , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/metabolismo , Humanos , Metilación/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Microscopía Fluorescente , Neuronas/citología , Neuronas/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Quinazolinas/farmacología , Interferencia de ARN , Precursores del ARN/metabolismo , ARN Interferente Pequeño/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Tretinoina/farmacologíaRESUMEN
Alternative splicing contributes to cell type-specific transcriptomes. Here, we show that changes in intragenic chromatin marks affect NCAM (neural cell adhesion molecule) exon 18 (E18) alternative splicing during neuronal differentiation. An increase in the repressive marks H3K9me2 and H3K27me3 along the gene body correlated with inhibition of polymerase II elongation in the E18 region, but without significantly affecting total mRNA levels. Treatment with the general DNA methylation inhibitor 5-azacytidine and BIX 01294, a specific inhibitor of H3K9 dimethylation, inhibited the differentiation-induced E18 inclusion, pointing to a role for repressive marks in sustaining NCAM splicing patterns typical of mature neurons. We demonstrate that intragenic deployment of repressive chromatin marks, induced by intronic small interfering RNAs targeting NCAM intron 18, promotes E18 inclusion in undifferentiated N2a cells, confirming the chromatin changes observed upon differentiation to be sufficient to induce alternative splicing. Combined with previous evidence that neuronal depolarization causes H3K9 acetylation and subsequent E18 skipping, our results show how two alternative epigenetic marks regulate NCAM alternative splicing and E18 levels in different cellular contexts.
Asunto(s)
Empalme Alternativo/fisiología , Diferenciación Celular/fisiología , Cromatina/genética , Epigénesis Genética/fisiología , Moléculas de Adhesión de Célula Nerviosa/genética , Neuronas/fisiología , Empalme Alternativo/genética , Animales , Azacitidina/farmacología , Azepinas/farmacología , Diferenciación Celular/genética , Línea Celular Tumoral , Inmunoprecipitación de Cromatina , Metilación de ADN/efectos de los fármacos , Cartilla de ADN/genética , Epigénesis Genética/genética , Exones/genética , Ratones , Quinazolinas/farmacología , ARN Interferente Pequeño/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Análisis de Secuencia de ADNRESUMEN
Splicing and alternative splicing are involved in the expression of most human genes, playing key roles in differentiation, cell cycle progression, and development. Misregulation of splicing is frequently associated to disease, which imposes a better understanding of the mechanisms underlying splicing regulation. Accumulated evidence suggests that multiple trans-acting factors and cis-regulatory elements act together to determine tissue-specific splicing patterns. Besides, as splicing is often cotranscriptional, a complex picture emerges in which splicing regulation not only depends on the balance of splicing factor binding to their pre-mRNA target sites but also on transcription-associated features such as protein recruitment to the transcribing machinery and elongation kinetics. Adding more complexity to the splicing regulation network, recent evidence shows that chromatin structure is another layer of regulation that may act through various mechanisms. These span from regulation of RNA polymerase II elongation, which ultimately determines splicing decisions, to splicing factor recruitment by specific histone marks. Chromatin may not only be involved in alternative splicing regulation but in constitutive exon recognition as well. Moreover, splicing was found to be necessary for the proper 'writing' of particular chromatin signatures, giving further mechanistic support to functional interconnections between splicing, transcription and chromatin structure. These links between chromatin configuration and splicing raise the intriguing possibility of the existence of a memory for splicing patterns to be inherited through epigenetic modifications.
Asunto(s)
Cromatina , Empalme del ARN , Empalme Alternativo , Secuencia de Bases , Humanos , Precursores del ARN/genética , Precursores del ARN/metabolismo , Análisis de Secuencia de ARN , Transcripción GenéticaRESUMEN
Alternative splicing has emerged as a key contributor to proteome diversity, highlighting the importance of understanding its regulation. In recent years it became apparent that splicing is predominantly cotranscriptional, allowing for crosstalk between these two nuclear processes. We discuss some of the links between transcription and splicing, with special emphasis on the role played by transcription elongation in the regulation of alternative splicing events and in particular the kinetic model of alternative splicing regulation. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
Asunto(s)
Empalme Alternativo/fisiología , Elongación de la Transcripción Genética/fisiología , Empalme Alternativo/genética , Animales , Cromatina/química , Cromatina/metabolismo , Cromatina/fisiología , Humanos , Cinética , Modelos Biológicos , Unión Proteica/fisiología , ARN Polimerasa II/metabolismo , ARN Polimerasa II/fisiologíaRESUMEN
Timing of breeding to an optimal season is a requirement for a successful reproductive outcome in seasonally breeding species. Photoperiodic signals are capable of modifying the reproductive behaviour and reproductive systems in several vertebrate species. The cichlid fish Cichlasoma dimerus shows highly organized breeding activities and different social status. The aim of this study is to test whether C. dimerus reproductive behaviour (male aggressive behaviour and female choice) and reproductive physiology (GnRH3 morphometric parameters, pituitary hormones content and organ-somatic indexes) are modulated by photoperiod. Before spawning, dominant pairs were isolated and kept in opposite tanks of 20 l for one week, so they could see each other but not physically interact. Afterwards, a group was exposed for four weeks to a short photoperiod (8h light:16 h dark) (short photoperiod exposed animals: SP) while another group was exposed to a long photoperiod (14 h light:10h dark) (long photoperiod exposed animals: LP). Temperature was maintained constant. Behavioural experiments showed that male aggression related to territory selection and its defence is reduced in SP males. Further, SP females were never chosen. At the brain level we demonstrated that GnRH3 neuronal optical density of staining was reduced. Finally, at the pituitary level we showed that SP males showed low levels of beta-LH, PRL and GH in the pituitary, and that SP females showed no significant differences in the pituitary content of any hormone. Taken all together these results suggest that in C. dimerus the photoperiod is a relevant environmental cue related to reproductive behaviour and physiology.