Project description:With the advent of exome sequencing, a growing number of children are being identified with de novo loss of function mutations in the large GTPase essential for mitochondrial fission - Dynamin Related Protein 1 (DRP1); these mutations result in severe neurodevelopmental phenotypes such as developmental delay, optic atrophy, and epileptic encephalopathies. Though it is established that mitochondrial fission is an essential precursor to the rapidly changing metabolic needs of the developing cortex, it is not understood how identified mutations in different domains of DRP1 uniquely disrupt cortical development and synaptic maturation. We leveraged the power of both high-resolution imaging and induced pluripotent stem cells (iPSCs) harboring DRP1 mutations in either the GTPase or stalk domains to model early stages of cortical development. Transcriptional profiling of mutant DRP1 cortical neurons during maturation, as well as imaging of organelle dynamics and neuronal synapses, strongly suggests that altered mitochondrial morphology of DRP1 mutant neurons affect synaptic development leading to pathogenic dysregulation of synaptic activity.
Project description:We search for developmental changes specific to humans by examining gene expression profiles in the human, chimpanzee and rhesus macaque prefrontal and cerebellar cortex. In both brain regions, developmental patterns were more evolved in humans than in chimpanzees. The major human specific genes in prefrontal cortex was enriched in neuronal functions and regulated by several transcription factors, which were previously implicated in regulation of neuronal functions. To confirm neuronal function of the human prefrontal cortex specific genes, we identifed response genes upon neuronal activation in mouse cortical neurons. Our results show that human specific genes are enriched in the response genes upon neuronal activation, implying the function of human prefrontal cortex specific genes in synaptic development. The cortical neurons from E15 mouse were isolated and cultured. We then exposed neurons to bicuculline (Bic), or potassium chloride (KCl), or without treatment. The cultured neurons under each group were hybridized to Agilent whole mouse genome oligo microarray (4x44k).
Project description:Biallelic mutations in the gene that encodes the enzyme N-glycanase 1 (NGLY1) cause a rare disease with multi-symptomatic features including developmental delay, intellectual disability, neuropathy and seizures. NGLY1’s activity in human neural cells is currently not well understood. To understand how NGLY1 gene loss leads to the specific phenotypes of NGLY1 deficiency, we employed direct conversion of NGLY1 patient-derived induced pluripotent stem cells (iPSCs) to functional cortical neurons. Transcriptomic, proteomic, and functional studies of iPSC-derived neurons lacking NGLY1 function revealed several major cellular processes that were altered, including protein aggregate-clearing functionality, mitochondrial homeostasis, and synaptic dysfunctions. These phenotypes were rescued by introduction of a functional NGLY1 gene and were observed in iPSC-derived mature neurons, but not astrocytes. Finally, laser capture microscopy followed by mass spectrometry provided detailed characterization of the composition of protein aggregates specific to NGLY1-deficient neurons. Future studies will harness this knowledge for therapeutic development.
Project description:Two key paradigms for examining activity-dependent development of primary visual cortex (V1) involve either reduction of activity in both eyes via dark-rearing (DR) or imbalance of activity between the two eyes via monocular deprivation (MD).,Combining DNA microarray analysis with computational approaches, RT-PCR, immunohistochemistry and physiological imaging, we find that DR leads to (i) upregulation of genes subserving synaptic transmission and electrical activity, consistent with a coordinated response of cortical neurons to reduction of visual drive, and (ii) downregulation of parvalbumin, implicating parvalbumin-expressing neurons as underlying the delay in cortical maturation after DR. MD partially activates homeostatic mechanisms but differentially upregulates gene systems related to growth factors and neuronal degeneration, consistent with reorganization of connections after MD. A binding protein of Insulin-like Growth Factor 1 is highly upregulated after MD, and exogenous application of IGF1 prevents the physiological effects of MD on ocular dominance plasticity examined in vivo.
Project description:We search for developmental changes specific to humans by examining gene expression profiles in the human, chimpanzee and rhesus macaque prefrontal and cerebellar cortex. In both brain regions, developmental patterns were more evolved in humans than in chimpanzees. To distinguish whether the human specific developmental pattern represent novel human-specific developmental patterns or a shift in the timing of the existing patterns, we measured mRNA expression patterns in macaque brains from prenatal to neonatal. Our results show that the major human-specific developmental patterns identified in the PFC reflects an extreme shift in timing of synaptic development.
Project description:We search for developmental changes specific to humans by examining gene expression profiles in the human, chimpanzee and rhesus macaque prefrontal and cerebellar cortex. In both brain regions, developmental patterns were more evolved in humans than in chimpanzees. To distinguish whether the human specific developmental pattern represent novel human-specific developmental patterns or a shift in the timing of the existing patterns, we measured mRNA expression patterns in macaque brains from prenatal to neonatal. Our results show that the major human-specific developmental patterns identified in the PFC reflects an extreme shift in timing of synaptic development. Rhesus macaque post-mortem brain samples from the superior frontal gyrus region of the prefrontal cortex were collected. Six fetal and six newborn samples were used. RNA extracted from the dissected tissue was hybridized to Affymetrix® Human Gene 1.0 ST arrays.
Project description:The mammalian cortex is the structural basis for learning, cognition, and movement coordination. Dysgenesis of axon dendrites and synapses in cortical neurons can hinder learning and cognitive development, leading to epilepsy. Transcription factor Otx1 plays an important role in the development of the morphology and electrophysiological activity of cortical neurons and is associated with the occurrence of epilepsy. Abnormal synaptic pruning has been proposed to be one of the molecular mechanisms underlying epilepsy. Otx1 mutant mice leads to defective axonal pruning and changes the excitability and synaptic connections of the cortical neurons. However, little is known about the molecular pathways through which the loss of Otx1 causes epilepsy. On this basis, we found that the density and morphology of dendritic spines and microglia in Otx1 mutant mice changed significantly. TMT analysis of synaptic proteins reveals that Otx1 regulates the structure and function of cortical neurons and synaptic characteristics by regulating microglia-mediated synaptic pruning through the complement system, which also has important theoretical significance and application value for effective prevention and treatment of epilepsy.
Project description:Biallelic mutations in the gene that encodes the enzyme N-glycanase 1 (NGLY1) cause a rare disease with multi-symptomatic features including developmental delay, intellectual disability, neuropathy and seizures. NGLY1’s activity in human neural cells is currently not well understood. To understand how NGLY1 gene loss leads to the specific phenotypes of NGLY1 deficiency, we employed direct conversion of NGLY1 patient-derived induced pluripotent stem cells (iPSCs) to functional cortical neurons. Transcriptomic, proteomic, and functional studies of iPSC-derived neurons lacking NGLY1 function revealed several major cellular processes that were altered, including protein aggregate-clearing functionality, mitochondrial homeostasis, and synaptic dysfunctions. These phenotypes were rescued by introduction of a functional NGLY1 gene and were observed in iPSC-derived mature neurons, but not astrocytes. Finally, laser capture microscopy followed by mass spectrometry provided detailed characterization of the composition of protein aggregates specific to NGLY1-deficient neurons. Future studies will harness this knowledge for therapeutic development.
Project description:We investigated molecular changes during human, chimpanzee, and rhesus macaque postnatal brain development at the transcriptome, proteome, and metabolome levels in two brain regions: the prefrontal cortex (PFC) that is involved in several human-specific cognitive processes, and the cerebellar cortex (CBC) that may be functionally more conserved. We find a nearly three-fold excess of human-specific gene expression changes in PFC compared to CBC. The most prominent human-specific mRNA expression pattern in the PFC is a developmental delay of approximately 5 years in the expression of genes associated with learning and memory, such as synaptic transmission and long-term potentiation. This pattern is supported by correlated changes in concentrations of proteins and the respective neurotransmitters and its magnitude is beyond the shift expected from the life-histories of the species. Mechanistically, it might be driven by change in timing of expression of four or more transcription factors. We speculate that delayed synaptic maturation in PFC may play a role in the emergence of human-specific cognitive abilities. Keywords: Age series Human, chimpanzee and rhesus macaque post-mortem brain samples from the cerebellar cortex were collected. The age ranges of the individuals in all three species covered the respective species' postnatal maturation period from infancy to old adulthood. RNA extracted from the dissected tissue was hybridized to Affymetrix® Human Gene 1.0 ST arrays. CBC samples.
Project description:Experience and activity-dependent transcription is a candidate mechanism to mediate development and refinement of specific cortical circuits. Here we provide evidence that the activity-dependent transcription factor Myocyte-Enhancer Factor 2C (MEF2C) is required in both presynaptic layer 4 (L4) and postsynaptic L2/3 somatosensory (S1) cortical neurons for development of their synaptic connection. In contrast, synaptic inputs from local L2/3, contralateral S1, or ipsilateral frontal/motor cortex are unaffected by postsynaptic Mef2c deletion in L2/3 neurons. Postsynaptic MEF2C is required for L4 to L2/3 synapse function during, but not after, an early postnatal, experience-dependent period. Furthermore, homozygous and heterozygous Mef2c deletion in presynaptic L4 neurons weakens L4 to L2/3 excitatory synaptic inputs by decreasing presynaptic release probability. Our results suggested that experience or activity-dependent transcriptional activation of MEF2C promotes development of L4→L2/3 synapses. In support of this idea, expression of transcriptionally active MEF2C (MEF2C-VP16) rescued weak L4 to L2/3 synaptic strength in sensory deprived mice. Consistent with a presynaptic function for MEF2C, we find that MEF2C regulates the activity-dependent expression of many presynaptic assembly genes, including transsynaptic cell adhesion proteins and regulators of neurotransmitter release. This work provides mechanistic insight into the experience-dependent development of specific cortical circuits.