Nuclear import receptors (NIRs) not only transport RNA-binding proteins (RBPs) but also modify phase transitions of RBPs by recognizing nuclear localization signals (NLSs). Toxic arginine-rich poly-dipeptides from C9orf72 interact with NIRs and cause nucleocytoplasmic transport deficit. However, the molecular basis for the toxicity of arginine-rich poly-dipeptides toward NIRs function as phase modifiers of RBPs remains unidentified. Here we show that arginine-rich poly-dipeptides impede the ability of NIRs to modify phase transitions of RBPs. Isothermal titration calorimetry and size-exclusion chromatography revealed that proline:arginine (PR) poly-dipeptides tightly bind karyopherin-β2 (Kapβ2) at 1:1 ratio. The nuclear magnetic resonances of Kapβ2 perturbed by PR poly-dipeptides partially overlapped with those perturbed by the designed NLS peptide, suggesting that PR poly-dipeptides target the NLS binding site of Kapβ2. The findings offer mechanistic insights into how phase transitions of RBPs are disabled in C9orf72-related neurodegeneration.

The brainstem is a posterior region of the brain, composed of three parts, midbrain, pons, and medulla oblongata. It is critical in controlling heartbeat, blood pressure, and respiration, all of which are life-sustaining functions, and therefore, damages to or disorders of the brainstem can be lethal. Brain organoids derived from human pluripotent stem cells (hPSCs) recapitulate the course of human brain development and are expected to be useful for medical research on central nervous system disorders. However, existing organoid models are limited in the extent hPSCs recapitulate human brain development and hence are not able to fully elucidate the diseases affecting various components of the brain such as brainstem. Here, we developed a method to generate human brainstem organoids (hBSOs), containing midbrain/hindbrain progenitors, noradrenergic and cholinergic neurons, dopaminergic neurons, and neural crest lineage cells. Single-cell RNA sequence (scRNA-seq) analysis, together with evidence from proteomics and electrophysiology, revealed that the cellular population in these organoids was similar to that of the human brainstem, which raises the possibility of making use of hBSOs in investigating central nervous system disorders affecting brainstem and in efficient drug screenings.

Ischemic stroke is one of the most common neurological diseases. However, the impact of ischemic stroke on human cerebral tissue remains largely unknown due to a lack of ischemic human brain samples. In this study, we applied cerebral organoids derived from human induced pluripotent stem cells to evaluate the effect of oxygen-glucose deprivation/reoxygenation (OGD/R). Pathway analysis showed the relationships between vitamin digestion and absorption, fat digestion and absorption, peroxisome proliferator-activated receptor (PPAR) signaling pathway, and complement and coagulation cascades. Combinational verification with transcriptome and gene expression analysis of different cell types revealed fatty acids-related PPAR signaling pathway and pyruvate kinase isoform M2 (PKM2) as key markers of neuronal cells in response to OGD/R. These findings suggest that, although there remain some limitations to be improved, our ischemic stroke model using human cerebral organoids would be a potentially useful tool when combined with other conventional two-dimensional (2D) mono-culture systems.

The brainstem controls heartbeat, blood pressure and respiration, which are life-sustaining functions, therefore, disorders of the brainstem can be lethal. Brain organoids derived from human pluripotent stem cells recapitulate the course of human brain development and are expected to be useful for medical research on central nervous system disorders. However, existing organoid models have limitations, hampering the elucidation of diseases affecting specific components of the brain. . Here, we developed a method to generate human brainstem organoids (hBSOs), containing neural crest stem cells as well as midbrain/hindbrain progenitors, noradrenergic and cholinergic neurons, and dopaminergic neurons, demonstrated by specific electrophysiological signatures. Single-cell RNA sequence analysis, together with proteomics and electrophysiology, revealed that the cellular population in these organoids was similar to that of the human brainstem and neural crest, which raises the possibility of making use of hBSOs in grafting for transplantation, efficient drug screenings and modeling the neural crest diseases. IntroductionThe brainstem is a posterior region of the brain between the deep structures of the cerebral hemispheres. It connects the cerebrum with the spinal cord and is divided into three parts: midbrain, pons and medulla oblongata. They contain multiple nuclei and small fiber tracts widely projecting to the cerebrum cortex, basal ganglia and other parts of the cerebrum. Brainstem functions such as alertness, heartbeat, blood pressure and respiration are considered to be more vital for life than that of the cortex. Therefore, damages to or disorders of brainstem such as infarction, hemorrhage, tumors, or any neurodegenerative diseases may lead to death.Of those, Parkinson's disease (PD) is the most well-known degenerative disease, showing progressive voluntary movement impairments, including rigidity, akinesia, tremor, and postural instability. These symptoms are caused by the loss of dopaminergic neurons at midbrain substantia nigra. In addition, non-motor symptoms, such as autonomic dysfunction, sleep disorder, and depression in PD patients, are thought to be derived from impairments of the serotonergic or noradrenergic system in the brainstem. However, the mechanisms driving these symptoms have yet to be determined. Hence, we need the development of models that can recapitulate the human midbrain and surrounding brainstem to elucidate the process of neural degeneration in this area.Recent progress on protocols for inducing organs in-a-dish (organoids) provides potentials for the modeling of various diseases (Clevers, 2016). Organoids mimic the structure of organs Eura, Matsui, Luginbühl et al.

Ischemic stroke is one of the most common neurological disease. However, the impact of ischemic stroke on human cerebral tissue remains largely unknown; due to a lack of ischemic human brain samples. In this study, we used cerebral organoids derived from human induced pluripotent stem cells to evaluate the effect of oxygen-glucose deprivation/reoxygenation (OGD/R). We identified 15 differentially expressed genes (DEGs); and found that all the DEGs were downregulated. Pathway analysis showed the relationship of vitamin digestion and absorption, fat digestion and absorption, peroxisome proliferator-activated receptor signaling pathway, and complement and coagulation cascades. These findings indicate the mechanisms underlying ischemic injury in human cerebral tissue.