Project description:Visual system development is light-experience dependent, which strongly implicates epigenetic mechanisms in light-regulated maturation. Among many epigenetic processes, genomic imprinting is an epigenetic mechanism through which monoallelic gene expression occurs in a parent-of-origin-specific manner. It is unknown if genomic imprinting contributes to visual system development. We profiled the transcriptome and imprintome during critical periods of mouse visual system development under normal- and dark-rearing conditions using B6/CAST F1 hybrid mice. We identified experience-regulated, isoform-specific, and brain region-specific imprinted genes. We also found imprinted microRNAs were predominantly clustered into the Dlk1-Dio3 imprinted locus with light experience affecting some imprinted miRNA expression. Our findings provide the first comprehensive analysis of light-experience regulation of the transcriptome and imprintome during critical periods of visual system development. Our results may contribute to therapeutic strategies for visual impairments and circadian rhythm disorders resulting from a dysfunctional imprintome.
Project description:Throughout childhood and adolescence, periods of heightened neuroplasticity are critical for the development of healthy brain function and behavior. Given the high prevalence of neurodevelopmental disorders such as autism, identifying disruptors of developmental plasticity represents an essential step for developing strategies for prevention and intervention. Applying a novel computational approach that systematically assessed connections between 436 transcriptional signatures of disease and multiple signatures of neuroplasticity, we identified inflammation as a common pathological process central to a diverse set of diseases predicted to dysregulate plasticity signatures. We tested the hypothesis that inflammation disrupts developmental cortical plasticity in vivo using the mouse ocular dominance model of experience-dependent plasticity in primary visual cortex. We found administration of systemic lipopolysaccharide suppressed plasticity during juvenile critical period with accompanying transcriptional changes in a particular set of molecular regulators within primary visual cortex. These findings suggest inflammation may have unrecognized adverse consequences on the postnatal developmental trajectory and indicates that treating inflammation may reduce the burden of neurodevelopmental disorders.
Project description:Brain postnatal development is characterized by critical periods of experience dependent remodeling. Maturation of local circuits inhibitory neurons terminate this period of enhanced plasticity. Astroglial cells are known to influence excitatory and inhibitory synaptic transmission as well as network activity through active signaling mechanisms. Although these can be developmentally regulated, the role of astrocytes in the timing of post-natal critical period is unknown. Here we show in the visual cortex that astrocytes con-trol the maturation of inhibitory neurons and thereby closure of the critical period. We uncover a novel underlying pathway involving regulation of the extracellular matrix that allows interneurons maturation via astroglial connexin signaling. We find that timing of the critical period closure is controlled by a marked upregulation of the astroglial protein connexin 30 that inhibits expression of the matrix degrading enzyme MMP9 through the RhoA-GTPase pathway. Our results thus demonstrate that astrocytes not only influ-ence neuronal activity but are also key elements in the experience–dependent wiring of brain circuits. Therefore, astrocytes represent a new cellular partner to consider in our understanding of the post-natal shaping of neuronal activities, hence providing a new target to alleviate malfunctions associated to im-paired closure of the critical period and settling of synaptic circuits.
Project description:Autism spectrum disorders such as Rett syndrome (RTT) have been hypothesized to arise from defects in experience-dependent synapse maturation. RTT is caused by mutations in MECP2, a nuclear protein that becomes phosphorylated at S421 in response to neuronal activation. We show here that disruption of MeCP2 S421 phosphorylation in vivo results in defects in synapse development and behavior, implicating activity-dependent regulation of MeCP2 in brain development and RTT. We investigated the mechanism by which S421 phosphorylation regulates MeCP2 function and show by chromatin immunoprecipitation-sequencing that this modification occurs on MeCP2 bound across the genome. The phosphorylation of MeCP2 S421 appears not to regulate the expression of specific genes; rather, MeCP2 functions as a histone-like factor whose phosphorylation may facilitate a genome-wide response of chromatin to neuronal activity during nervous system development. We propose that RTT results in part from a loss of this experience-dependent chromatin remodeling. Gene expression analysis of RNA isolated from P17 mouse visual cortex was performed comparing global gene expression between Wild-Type and MeCP2 S421A knock-in mice. We isolated RNA from the visual cortex of 4 wild-type and 4 MeCP2 S421A littermate P17 Mice, and analyzed mRNA expression using the Affymetrix Mouse Gene 1.0 ST microarray platform.
Project description:Hypoxic exposure during development can have a profound influence on offspring physiology, including cardiac dysfunction, yet many reptile embryos naturally experience periods of hypoxia in buried nests. American alligators experimentally exposed to developmental hypoxia demonstrate morphological and functional changes to the heart that persist into later life stages; however, the molecular bases of these changes remain unknown. We tested if targeted and persistent changes in steady-state protein expression underlie this hypoxic heart phenotype, using isobaric tags for relative and absolute quantitation (iTRAQ) proteomics. Alligator eggs were reared under normoxia or 10% hypoxia, then either sampled (embryo) or returned to normoxia for 2 years (juvenile). Three salient findings emerge from the integrated analysis of the 145 differentially expressed proteins in hypoxia-reared animals: (1) significant protein-protein interaction networks were identified only in up-regulated, indicating that the effects of developmental hypoxia are stimulatory and directed; (2) the up-regulated proteins substantially enriched processes related to protein turnover, cellular organization, and metabolic pathways, supporting increased resource allocation towards building and maintaining a higher functioning heart; and (3) the juvenile cardiac proteome retained many of the signature changes observed in embryonic hearts, supporting long-term reprogramming of cardiac myocytes induced by hypoxia during critical periods of development.
Project description:Juvenile primates develop myopia when their visual experience is degraded by lid fusion. In response to the abnormal visual input, retinal neural networks cause an excessive growth of the postequatorial segment of the eye, but the mechanism underlying this axial elongation is unknown. By combining analysis of gene expression, injection of the thymidine analog 5-bromo-2'-deoxyuridine and immunocytochemistry, we show that the retinal periphery in both juvenile rhesus macaques and green monkeys harbors a population of mitotically active neuroprogenitor cells that proliferate when the visual experience is altered by lid fusion. Furthermore, the number of dividing cells is highly correlated with the axial elongation of the eye and the resulting myopic refractive error. Thus, the retina undergoes active growth during the postnatal development of the primate eye. This growth is modulated by the visual input and accelerates considerably when the eye develops axial myopia. Keywords: disease state analysis
Project description:Zebrafish is an important model system for the study of vertebrate embryonic development and adaptive immunese response. Recent years have seen great advancement in the understanding of the regulatory mechanisms during zebrafish embryogenesis and immune processes, yet large gaps still remain in the functional pathways critical for each developmental stage, especially for the late embryonic development. We sequenced the polyA-extracted mRNA from 9 stages covering 7 major developmental periods of zebrafish. Whole genome gene expression pattern were analyzed to reveal unknown pathways or factors with implicated roles during each stage of vertebrate development. Analysis of total mRNA by highthroughput sequencing in 9 stages covering 7 periods during the embryonic and larval development of zebrafish
Project description:To identify regulators of activity-dependent neural progenitor cell fate, we used RNA-Seq to profile the transcriptomes of proliferating neural progenitor cells and newly-differentiated immature neurons. We identified six DE transcription factors which are predicted to regulate the majority of the other DE transcripts. We investigated the effect of BRCA1 and ELK-1 on activity-regulated neurogenesis in the tadpole visual system and found that knockdown of either BRCA1 or ELK-1 altered the fates of neural progenitor cells, and furthermore that the effects of visual experience on neurogenesis depend on BRCA1 expression, while the effects of visual experience on neuronal differentiation depend on ELK-1 expression. These studies provide insight into the potential mechanisms by which neural activity affects neural progenitor cell fate.
Project description:Visual cortical circuits show profound plasticity during early life and are later stabilized by molecular "brakes" limiting excessive circuit rewiring beyond a critical period. How the appearance of these factors is coordinated during the transition from development to adulthood remains unknown. We analyzed the role of miR-29a, a miRNA targeting factors involved in several important pathways for plasticity such as extracellular matrix and chromatin regulation. We found that visual cortical miR-29a expression in the visual cortex dramatically increases with age, but it is not experience-dependent. Precocious high levels of miR-29a induced by targeted intracortical injections of a miR-29a mimic blocked ocular dominance plasticity and caused an early appearance of perineuronal nets. Conversely, inhibition of miR-29a in adult mice using LNA antagomirs activated ocular dominance plasticity, reduced perineuronal net intensity and number, and changed their chemical composition restoring permissive low chondroitin 4-O-sulfation levels characteristic of juvenile mice. Activated adult plasticity had the typical functional and proteomic signature of juvenile plasticity. Transcriptomic and proteomic studies indicated that miR-29a manipulation regulates the expression of plasticity factors acting at different cellular levels, from chromatin regulation to synaptic organization and extracellular matrix remodeling. Intriguingly, the projection of miR-29a regulated gene dataset onto cell-specific transcriptomes revealed that parvalbumin-positive interneurons and oligodendrocytes were the most affected cells. Overall, miR29a is a master regulator of the age-dependent plasticity brakes promoting stability of visual cortical circuits.