Academic literature on the topic 'IPSC-derived neurons'

Parkinson's disease (PD) is characterised by the loss of dopaminergic neurons in the Substantia Nigra pars compacta in the midbrain and the presence of intracellular aggregates, known as Lewy bodies (LBs), in the surviving neurons. The aetiology of PD is unknown but a causative role for α-Synuclein (SNCA) has been proposed. Although the function of αSyn is not well understood, a number of pathological mechanisms associated with αSyn toxicity have been proposed. In this study, nine induced pluripotent stem cells (iPSCs) lines from healthy individuals and PD patients carrying the A53T SNCA mutation or a triplication of SNCA were differentiated to dopaminergic neurons (iDAn). All iPSC lines differentiated with similar efficiency to iDAn, indicating that they could be used for phenotypic analysis. Quantification of αSyn expression showed increased αSyn intracellular staining and the novel detection of increased αSyn oligomerization in PD iDAn. Analysis of mitochondrial respiration found a decrease in basal respiration, maximal respiration, ATP production and spare capacity in PD iDAn, but not in undifferentiated iPSCs, indicating the cell-type specificity of these defects. Decreased phosphorylation of dynamin-1-like protein at Ser616 (DRP1^Ser616) and increased levels of Peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) in A53T SNCA iDAn suggest a new pathological mechanism linking αSyn to the imbalance in mitochondria homeostasis. Markers of endoplasmic reticulum (ER) stress were found to be up-regulated, along with increased β- Glucocerebrosidase (GBA) activity, perturbation of autophagy and decreased expression of fatty acids binding protein 7 (FAPB7) in PD iDAn. Lastly, lentiviral vectors for RNAi-mediated knockdown of αSyn were developed and these reduced αSyn protein levels in iDAn, resulting in increased expression of FABP7. These results describe a novel functional link between αSyn and FABP7. This work demonstrates that iDAn are a promising and relevant in vitro cell model for studying cellular dysfunctions in PD pathology, and the phenotypic analysis of A53T SNCA and SNCA triplication iDAn enabled the detection of novel pathological mechanisms associated with PD.

Parkinson's disease (PD) is a common neurodegenerative disorder, characterised by preferential loss of ventral midbrain dopaminergic (vmDA) neurons in the substantia nigra pars compacta (SNc). The majority of PD cases have unknown aetiology; however, between 5-10% arise due to known genetic mutations, the most common of which are found in the LRRK2 gene. LRRK2 is expressed in neurons and glia in the human brain; therefore, cell-autonomous and/or non-cell autonomous effects may participate in LRRK2-mutation-mediated degeneration of vmDA neurons. This study set out to understand the effects of LRRK2 mutations on human vmDA neurons and midbrain astrocytes, and to shed new light on the mechanisms of PD pathogenesis. To achieve this goal, differentiation protocols were generated to produce vmDA neurons and midbrain patterned (MP) astrocytes from induced pluripotent stem cells (iPSCs). iPSCs from patients carrying the LRRK2-G2019S mutation were differentiated into both cell types, and hypothesis-driven analysis of cellular functions including autophagy, mitochondrial respiration, glycolysis, and cellular migration was conducted; however, no disease phenotypes were observed. Following this, proteomics and transcriptomics techniques were then used to analyse the effects of the LRRK2-G2019S mutation in an unbiased manner. In the iPSC-derived MPastrocyte cultures, this technique highlighted stochastic X-chromosome reactivation events that led to difficulties in interpreting the resulting data; however, in the iPSC-derived vmDA-neuron cultures, LRRK2-G2019S-mediated inhibition of endocytosis and axon guidance was identified. These findings were found to be consistent in iPSC-derived vmDA-neuron cultures carrying the LRRK2-R1441C mutation, suggesting that these two mutations exert their pathogenic effects through similar mechanisms. Finally, phosphoproteomics analysis of iPSC-derived vmDA-neuron cultures was conducted to identify bone fide LRRK2-kinase substrates. Eleven potential LRRK2- kinase substrates were identified, nine of which have been previously shown to participate in endocytic vesicle trafficking, neurite outgrowth, and synaptic function. The findings of this study suggest that LRRK2 has neuron-specific functions, and that its mutations contribute to neurodegeneration in a cell-autonomous manner.

Rett syndrome is a severe neurodevelopmental disorder. The condition affects approximately one in every 10.000 females and is only rarely seen in males. Causative mutations in the transcriptional regulator MeCP2 have been identified in more than 95% of classic Rett patients; mutations in CDKL5 are responsible for the early onset seizures Rett variant and mutations in FOXG1 gene lead to the congenital Rett variant. To shed light on molecular mechanisms underlying Rett syndrome onset and progression in disease-relevant cells, we took advantage of the breakthrough genetic reprogramming technology and we investigated changes in iPSC-derived neurons from patients with different MECP2 and FOXG1 mutations and in the brain of Foxg1+/- mice. In total brains from Foxg1+/ − mutants we noticed a statistically significant overexpression of a group of neuropeptides expressed in the basal ganglia, cortex, hippocampus and hypothalamus: Oxytocin (Oxt), Arginine vasopressin (Avp) and Neuronatin (Nnat).Moreover, in iPSC-derived neuronal precursors and neurons mutated in FOXG1 and in Foxg1+/− mouse embryonic brain (E11.5) compared to wild type controls we found an increase in the expression of GluD1 and inhibitory synaptic markers, such as GAD67 and GABA AR-α1 and a decreased expression of excitatory synaptic markers, such as VGLUT1, GluA1, GluN1 and PSD-95, suggesting an excitation/inhibition imbalance in the developing brain of the congenital RTT variant. Furthermore, we investigated transcriptome changes in neurons differentiated from MECP2 mutated iPSC-derived neurons and we noticed a prominent GABAergic circuit disruption and a perturbation of cytoskeleton dynamics. In particular, in MECP2-mutated neurons we identified a significant decrease of acetylated α-tubulin which can be reverted by treatment with a selective inhibitor of HDAC6, the main α-tubulin deacetylase. Taken togheter, these findings contribute to shed light on Rett pathogenic mechanisms and provide hints for the definition of new therapeutic strategies for Rett syndrome.

The advent of human induced pluripotent stem cell (iPSC) technology has allowed for unprecedented investigation into the pathophysiology of human neurological and psychiatric diseases. Use of human iPSC-derived neural cells to study disease is complicated by the genetic heterogeneity of cell lines and diversity of differentiation protocols. Here, I address issues surrounding neuropsychiatric disease modeling with human iPSCs. Dozens of published protocols exist to differentiate iPSCs into forebrain neuronal cultures. Among the factors that distinguish these methods are: use of small molecules, monolayer vs. aggregate culture, choice of plating substrates, method of NPC isolation, and glial co-culture. Each of these factors is evaluated here, creating a resource that directly compares a variety of differentiation procedures. The most efficient and reproducible method was an embryoid aggregate differentiation protocol, including aggregate plating onto a Matrigel substrate, enzymatic neural rosette selection, and neuronal dissociation and plating onto Matrigel. This optimized protocol is used to model a schizophrenia-relevant mutation in human neural cells. Genetic and clinical association studies have identified disrupted-in-schizophrenia 1 (DISC1) as a strong candidate risk gene for major mental illness. DISC1 was initially associated with mental illness upon the discovery that its coding sequence is interrupted by a balanced chr(1;11) translocation in a Scottish family, in which the translocation cosegregates with psychiatric disorders. I investigate the functional and biochemical consequences of DISC1 interruption in human neurons using TALENs or CRISPR-Cas9 to introduce DISC1 frameshift mutations into iPSCs. I show that disease-relevant DISC1 targeting results in decreased DISC1 protein expression by nonsense-mediated decay, increases baseline Wnt signaling in neural progenitor cells, and causes a shift in neural cell fate. DISC1-dependent Wnt signaling and cell fate changes can be reversed by antagonizing the Wnt pathway during a critical window in neural progenitor development. These experiments suggest that DISC1-disruption increases Wnt signaling, which alters the balance and identity of neural progenitors, thereby subtly modifying cell fate. These studies evaluate the use of multiple differentiation procedures in neural disease modeling, shed light on the roles of DISC1 during human brain development, and further our understanding of the pathogenesis of major mental illness.<br>Medical Sciences

Parkinson's disease (PD) is characterised by the selective loss of dopaminergic neurons of the substantia nigra pars compacta. Patients suffer from a progressive motor disorder, defined by the presence of rigidity, resting tremor and bradykinesia. Current treatment options, relieve symptoms for a limited period, but are not curative, as the underlying molecular causes of neurodegeneration are unknown. Several causative PD mutations have been identified and could provide insight into the defective molecular pathways in PD. Multiplication or missense mutation of the SNCA gene leads to autosomal dominant PD. Alpha-synuclein, encoded by the SNCA gene, is a defining component of proteinaceous deposits found in surviving neurons in PD and a central protein in PD aetiology. Induced pluripotent stem cells (iPSCs) self-renew indefinitely and generate all germ layer lineages. Human iPSCs derived from an individual with a genetic variant known to cause disease, provide a platform to investigate the molecular basis of disease. However, genetic variation between iPSC lines can lead to functional disparities, masking or accentuating disease-specific phenotypes. Genome engineering facilitates the generation of iPSCs which differ exclusively at the locus of interest, providing a genetically stable cellular model. iPSCs from an individual with a SNCA missense mutation, G51D, and an unaffected relative were characterised, demonstrating ex vivo pluripotency was established and dopaminergic neurons could be derived. The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system was exploited to introduce the G51D mutation into control iPSCs. Changes in dopamine turnover and protein metabolism were detected after differentiation of CRISPR-Cas9 generated iPSCs, now harbouring the heterozygote G51D mutation. A CRISPR-Cas9 G51D homozygote iPSC clone was generated and a reduction in the number of dopaminergic neurons produced observed. This study demonstrates human iPSCs can be used to detect phenotypic differences in specialised cells, despite the latency of PD, and before overt neurodegeneration.

IPSC-derived neurons and astrocytes: a novel patient-specific model to study the pre-degenerative molecular alteration in Parkinson's Disease<br>IPSC-derived neurons and astrocytes: a novel patient-specific model to study the pre-degenerative molecular alteration in Parkinson's Disease

Parkinson's disease (PD) primarily manifests as loss of motor control through the degeneration of nigrostriatal dopaminergic neurons. The microtubule-associated protein tau (MAPT) locus is highly genetically associated with PD, wherein the H1 haplotype confers disease risk and the H2 haplotype is protective. As this haplotype variation does not alter the amino acid sequence, disease risk may be conferred by altered gene expression, either of total MAPT or of specific isoforms, of which there are six in adult human brain. To investigate haplotype-specific control of MAPT expression in the neurons that die in PD, induced pluripotent stem cells (iPSCs) from H1/H2 heterozygous individuals were differentiated into dopaminergic neuronal cultures that expressed all six mature isoforms of MAPT after six months' maturation. A reporter construct using the human tyrosine hydroxylase locus was also generated to identify human dopaminergic neurons in mixed cultures. Haplotype-specific differences in the inclusion of exon 3 and total MAPT were observed in iPSC-derived dopaminergic neuronal cultures and a novel variant in MAPT intron 10 increased the inclusion of exon 10 by two-fold. RNA interference tools were generated to knockdown total MAPT or specific isoforms, wherein knockdown of the 4-repeat isoform of tau protein increased the velocity of axonal transport in iPSC-derived neurons. MAPT knockdown also reduced p62 levels, suggesting an impact of tau on macroautophagy, likely through altered axonal transport. These results demonstrate how variation at a disease susceptibility locus can alter gene expression, thereby impacting on neuronal function.