Zika Virus Disrupts Phospho-TBK1 Localization and Mitosis in Human Neuroepithelial Stem Cells and Radial Glia

The mechanisms underlying Zika virus (ZIKV)-related microcephaly and other neurodevelopment defects remain poorly understood. Here, we describe the derivation and characterization, including single-cell RNA-seq, of neocortical and spinal cord neuroepithelial stem (NES) cells to model early human neurodevelopment and ZIKV-related neuropathogenesis. By analyzing human NES cells, organotypic fetal brain slices, and a ZIKV-infected micrencephalic brain, we show that ZIKV infects both neocortical and spinal NES cells as well as their fetal homolog, radial glial cells (RGCs), causing disrupted mitoses, supernumerary centrosomes, structural disorganization, and cell death. ZIKV infection of NES cells and RGCs causes centrosomal depletion and mitochondrial sequestration of phospho-TBK1 during mitosis. We also found that nucleoside analogs inhibit ZIKV replication in NES cells, protecting them from ZIKV-induced pTBK1 relocalization and cell death. We established a model system of human neural stem cells to reveal cellular and molecular mechanisms underlying neurodevelopmental defects associated with ZIKV infection and its potential treatment.

Apical migration of nuclei during G2 is a prerequisite for all nuclear motion in zebrafish neuroepithelia

Nuclei in the proliferative pseudostratified epithelia of vastly different organisms exhibit a characteristic dynamics - the so-called interkinetic nuclear migration (IKNM). Although these movements are thought to be intimately tied to the cell cycle, little is known about the relationship between IKNM and distinct phases of the cell cycle and the role that this association plays in ensuring balanced proliferation and subsequent differentiation. Here, we perform a quantitative analysis of modes of nuclear migration during the cell cycle using a marker that enables the first unequivocal differentiation of all four phases in proliferating neuroepithelial cells in vivo. In zebrafish neuroepithelia, nuclei spend the majority of the cell cycle in S phase, less time in G1, with G2 and M being noticeably shorter still in comparison. Correlating cell cycle phases with nuclear movements shows that IKNM comprises rapid apical nuclear migration during G2 phase and stochastic nuclear motion during G1 and S phases. The rapid apical migration coincides with the onset of G2, during which we find basal actomyosin accumulation. Inhibiting the transition from G2 to M phase induces a complete stalling of nuclei, indicating that IKNM and cell cycle continuation cannot be uncoupled and that progression from G2 to M is a prerequisite for rapid apical migration. Taken together, these results suggest that IKNM involves an actomyosin-driven contraction of cytoplasm basal to the nucleus during G2, and that the stochastic nuclear movements observed in other phases arise passively due to apical migration in neighboring cells.

The simultaneous presence of neuroepithelial cells and neuroepithelial bodies in the respiratory gas bladder of the longnose gar, Lepisosteus osseus, and the spotted gar, L. oculatus

Anatomical and functional studies on the autonomic innervation as well as the location of airway receptors in the air-bladder of lepisosteids are very fragmentary. These water-breathing fishes share in common with the bichirs the presence of a glottis (not a ductus pneumaticus) opening into the esophagus. In contrast to a high concentration of neuroepithelial cells (NECs) contained in the furrowed epithelium in the lung of Polypterus, these cells are scattered as solitary cells in the glottal epithelium, and grouped to form neuroepithelial bodies (NEBs) in the mucociliated epithelium investing the main trabeculae in the air-bladder of Lepisosteus osseus and L. oculatus. The present immunohistochemical studies also demonstrated the presence of nerve fibers in the trabecular striated musculature and a possible relation to NEBs in these species, and identified immunoreactive elements of this innervation. Tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), 5-HT and neuropeptide immunoreactivities were detected in the intramural nerve fibers. 5-HT and VIP immunopositive nerve fibers are apparently associated with NEBs. TH, VIP and SP immunoreactivities are also present in nerve fibers coursing in the radially arranged striated muscle surrounding the glottis and its submucosa. 5-HT positive neurons are also found in submucosal and the muscle layers of the glottis. The physiological function of the adrenergic and inhibitory innervation of the striated muscle as well as the neurochemical coding and morphology of the innervation of the NEBs are not known. Future studies are needed to provide evidence for these receptors with the capacity of chemoreceptors and/or mechanoreceptors.

Microencephaly and microphthalmia in rat fetuses by busulfan

Microencephaly and microphthalmia in the embryos/fetuses from rats exposed to busulfan were histopathologically examined. Busulfan was intraperitoneally administered at 10 mg/kg on gestation days (Days) 12, 13 and 14, and then embryos/fetuses were harvested on Days 14.5, 15, 16 and 21. In the treated group on Day 21, all fetuses were small with reduced body weight, with microencephaly and microphthalmia. On Days 14.5, 15 and 16, apoptotic cells were increased in the neuroepithelium and the neural retina with a width reduction and a decrease in cell density, and the lens epithelial cells histopathologically. Mitotic inhibition was observed in the neuroepithelium, neural retina and equatorial zone of the lens. On Day 21, the cerebral cortex and the retina became markedly thinner. The lens fibers showed swollen, fragmentary and vacuolar formation in the cranial portion accompanied with small lens sizes. The anti-proliferative effects of busulfan brings about a lack of cell populations required for the normal organogenesis of the brain and eye, and leads to microencephaly and microphthalmia, featuring hypoplasia of cerebrum and hypoplasia of retina and lens with cataract, respectively.

Formation of Neuroepithelial Structures in Culture of Neural Stem Cells from Human Brain

Dissociated fetal brain cells in a floating culture form clusters and then neurospheres, some of which contain structures shaped as cell "rosettes". The cells in these "rosettes" are arranged radially around the central cavity, in which their apical processes form desmosome-like contacts. Mitotic division of cells in the "rosettes" is associated with migration of the nuclei, similarly to division of neuroepithelial cells in the neural tube during normal embryogenesis. These cells express nestin, a marker of neural stem cells. The cells in "rosettes" found after transplantation have similar characteristics.

Axon-like processes in type III cells of taste organs

Type III cells of the taste organs are widely considered to be chemoreceptors. The present study was performed on the frog taste disk and describes an axon-like process in type III cells, which often contains a bundle of densely-packed parallel microfilaments. These processes pass through the basal membrane of the gustatory epithelium, running into the lamina propria (transbasal membrane processes, tBMPs). In their intraepithelial tract, tBMPs contain dense-cored vesicles revealing their origin from type III cells. Type III cells showing both classic nonrigid processes (with vesicles and nerve contacts) and tBMPs are present. The connective tract of a tBMP usually contains dense-cored vesicles only in its proximal portion. In some cases, the connective tract of tBMPs is almost perpendicular to the basal lamina. In other cases, it runs parallel to and below the basal lamina. Some tBMPs contact nerve fibers running in the subepithelial connective tissue; the contact area is rather wide but evident synapse-like junctions were never detected. Contacts between tBMPs and nerve fibers innervating basal cells are also found. In conclusion, the data demonstrate the existence of epithelial cells resembling primitive neurons that display an apical dendrite and axon-like basal processes. Until now, it was not considered possible that epithelial receptor cells extend processes out of the epithelium.

Effects of Buyang Huanwu Decoction on neurite outgrowth and differentiation of neuroepithelial stem cells

To determine the effects of Buyang Huanwu Decoction (BYHWD), a traditional Chinese medicine, on neurite outgrowth and differentiation of neuroepithelial stem cells (NEPs), NEPs were isolated from embryonic neural tube and cultured in medium with rat serum containing BYHWD, which was prepared from rats administrated orally with BYHWD. The average neurite length of NEPs grew significantly longer in rat serum containing BYHWD than in control serum without BYHWD. More neurofilament (NF) positive cells and glial fibrillary acidic protein (GFAP) positive cells were detected in NEPs cultured in the presence of BYHWD. Besides, when cultured NEPs were loaded with Fluo-3-AM, the fluorescence intensity obtained from NEPs cultured in serum with BYHWD was significantly lower than that from NEPs cultured in control serum without BYHWD. Our results indicate that BYHWD could exert a promotion effect on neurite outgrowth and differentiation of NEPs.