Pip5k1γ regulates axon formation by limiting Rap1 activity.

During their differentiation, neurons establish a highly polarized morphology by forming axons and dendrites. Cortical and hippocampal neurons initially extend several short neurites that all have the potential to become an axon. One of these neurites is then selected as the axon by a combination of positive and negative feedback signals that promote axon formation and prevent the remaining neurites from developing into axons. Here, we show that Pip5k1γ is required for the formation of a single axon as a negative feedback signal that regulates C3G and Rap1 through the generation of phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Impairing the function of Pip5k1γ results in a hyper-activation of the Fyn/C3G/Rap1 pathway, which induces the formation of supernumerary axons. Application of a hyper-osmotic shock to modulate membrane tension has a similar effect, increasing Rap1 activity and inducing the formation of supernumerary axons. In both cases, the induction of supernumerary axons can be reverted by expressing constitutively active Pip5k. Our results show that PI(4,5)P2-dependent membrane properties limit the activity of C3G and Rap1 to ensure the extension of a single axon.

Endothelial PlexinD1 signaling instructs spinal cord vascularization and motor neuron development.

How the vascular and neural compartment cooperate to achieve such a complex and highly specialized structure as the central nervous system is still unclear. Here, we reveal a crosstalk between motor neurons (MNs) and endothelial cells (ECs), necessary for the coordinated development of MNs. By analyzing cell-to-cell interaction profiles of the mouse developing spinal cord, we uncovered semaphorin 3C (Sema3C) and PlexinD1 as a communication axis between MNs and ECs. Using cell-specific knockout mice and in vitro assays, we demonstrate that removal of Sema3C in MNs, or its receptor PlexinD1 in ECs, results in premature and aberrant vascularization of MN columns. Those vascular defects impair MN axon exit from the spinal cord. Impaired PlexinD1 signaling in ECs also causes MN maturation defects at later stages. This study highlights the importance of a timely and spatially controlled communication between MNs and ECs for proper spinal cord development.

Acute Hepatitis C After Penile Stem Cell Injection.

Hepatitis C is a viral infection that is transmitted via blood or other bodily fluids and usually manifests as a chronic infection. We present a unique case of acute hepatitis C from a penile stem cell injection. Although previous cases have reported the reactivation of chronic hepatitis C after hematopoietic stem cell transplantation, it is uncommon for hepatitis C to present acutely, especially in an immunocompetent patient. To our knowledge, this is the first case of acute hepatitis C after a penile stem cell injection.

Mask-Induced Partial Transection of the External Ear Requiring Complex Surgical Reconstruction.

During the COVID-19 pandemic, wearing masks to prevent the spread of infection has been imperative. Though many wear N-95 masks with circumferential head straps, the use of surgical ear loop-style masks has increased. Dermatologic complications, such as contact dermatitis, psoriasis, and local irritation, have been described in several reports. One such complication has been pressure injury to the external ear, secondary to friction from the ear loops. While external ear pressure ulcers caused by mask-wearing have already been observed, injuries extensive enough to require surgical reconstruction have yet to be described. Herein, we present a unique case of an elderly male with a severe external ear deformity caused by prolonged, uninterrupted mask-wearing that was treated with a complex ear reconstruction. The pressure caused a full-thickness erosion of the helical and conchal cartilage with partial auricle amputation from constant mask wear. We describe an unusual and interesting problem caused indirectly by the coronavirus pandemic and discuss potential methods to protect oneself against skin injury from mask usage while simultaneously preventing viral transmission.

Arterioureteral Fistula in the Setting of Radical Cystoprostatectomy and Ileal Conduit Creation.

Arterioureteral fistulas (AUF) following ileal conduit reconstruction are rare and not well-studied. We present a life-threatening bleed from an AUF due to an ileal conduit urinary diversion. In addition, we identify the challenges in the diagnostic process as well as management strategies. We present a 63-year-old male with ileal conduit reconstruction for bladder cancer with an AUF developing years after the reconstruction, which was ultimately managed with angioplasty.

COVID-19 Vaccine Cardiac Complications: A Case Series on Implications of Marijuana in Adolescents With Myopericarditis.

We report on two critically ill pediatric patients, aged 16 and 18 years, presenting with acute myopericarditis at a tertiary-care center in New Jersey, United States. Both patients had their severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations, tested negative for SARS-CoV-2, and shared only significant history of asthma. Clinical presentations were similar to acute onset chest pain that worsened with deep inspiration. One patient reported a history of vaping and escalating marijuana use several hours preceding presentation. Both patients had elevated troponin on admission and had ST-segment elevation on electrocardiogram (EKG), thus prompting admission to the pediatric intensive care unit (PICU) for cardiac monitoring. Myopericarditis has multiple etiologies and is a newly described rare complication of the SARS-CoV-2 vaccine. It can also occur as a complication of vaping and frequent marijuana drug use. Our paper highlights the importance of a detailed social and drug history in adolescents presenting with chest pain. The clinical characterization is necessary to promote better case definitions and the design of targeted interventions for this vulnerable group.

A Rare Cause of Breathlessness in a Patient on Hemodialysis.

Patients suffering from end stage renal disease (ESRD) often present to the emergency with breathlessness, mostly due to fluid overload. We report a rare case of recurrent unilateral massive pleural effusion in an ESRD patient on maintenance hemodialysis (MHD). The patient was on MHD thrice weekly for the last 2 years with right internal jugular vein (IJV) tunneled cuffed catheter (TCC). Chylothorax was identified as the cause of recurrent pleural effusion which was due to superior vena cava stenosis (SVCO). It was managed successfully by balloon venoplasty of SVC and anticoagulation. SVCO is a rare but a serious complication in patients on long term indwelling dialysis catheters. Physicians involved in the care of dialysis patients must be aware about complications of long term dialysis catheters like central vein stenosis. A strong suspicion of chylothorax should be reserved for a patient with recurrent unilateral pleural effusion and long term dialysis catheters.

The angiopoietin-Tie2 pathway regulates Purkinje cell dendritic morphogenesis in a cell-autonomous manner.

Neuro-vascular communication is essential to synchronize central nervous system development. Here, we identify angiopoietin/Tie2 as a neuro-vascular signaling axis involved in regulating dendritic morphogenesis of Purkinje cells (PCs). We show that in the developing cerebellum Tie2 expression is not restricted to blood vessels, but it is also present in PCs. Its ligands angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) are expressed in neural cells and endothelial cells (ECs), respectively. PC-specific deletion of Tie2 results in reduced dendritic arborization, which is recapitulated in neural-specific Ang1-knockout and Ang2 full-knockout mice. Mechanistically, RNA sequencing reveals that Tie2-deficient PCs present alterations in gene expression of multiple genes involved in cytoskeleton organization, dendritic formation, growth, and branching. Functionally, mice with deletion of Tie2 in PCs present alterations in PC network functionality. Altogether, our data propose Ang/Tie2 signaling as a mediator of intercellular communication between neural cells, ECs, and PCs, required for proper PC dendritic morphogenesis and function.

Oligodendrocyte precursor cell specification is regulated by bidirectional neural progenitor-endothelial cell crosstalk.

Neural-derived signals are crucial regulators of CNS vascularization. However, whether the vasculature responds to these signals by means of elongating and branching or in addition by building a feedback response to modulate neurodevelopmental processes remains unknown. In this study, we identified bidirectional crosstalk between the neural and the vascular compartment of the developing CNS required for oligodendrocyte precursor cell specification. Mechanistically, we show that neural progenitor cells (NPCs) express angiopoietin-1 (Ang1) and that this expression is regulated by Sonic hedgehog. We demonstrate that NPC-derived Ang1 signals to its receptor, Tie2, on endothelial cells to induce the production of transforming growth factor beta 1 (TGFß1). Endothelial-derived TGFß1, in turn, acts as an angiocrine molecule and signals back to NPCs to induce their commitment toward oligodendrocyte precursor cells. This work demonstrates a true bidirectional collaboration between NPCs and the vasculature as a critical regulator of oligodendrogenesis.

Reciprocal Interaction between Vascular Filopodia and Neural Stem Cells Shapes Neurogenesis in the Ventral Telencephalon.

Angiogenesis and neurogenesis are tightly coupled during embryonic brain development. However, little is known about how these two processes interact. We show that nascent blood vessels actively contact dividing neural stem cells by endothelial filopodia in the ventricular zone (VZ) of the murine ventral telencephalon; this association is conserved in the human ventral VZ. Using mouse mutants with altered vascular filopodia density, we show that this interaction leads to prolonged cell cycle of apical neural progenitors (ANPs) and favors early neuronal differentiation. Interestingly, pharmacological experiments reveal that ANPs induce vascular filopodia formation by upregulating vascular endothelial growth factor (VEGF)-A in a cell-cycle-dependent manner. This mutual relationship between vascular filopodia and ANPs works as a self-regulatory system that senses ANP proliferation rates and rapidly adjusts neuronal production levels. Our findings indicate a function of vascular filopodia in fine-tuning neural stem cell behavior, which is the basis for proper brain development.

Cellular and Molecular Mechanisms of Spinal Cord Vascularization.

During embryonic central nervous system (CNS) development, the neural and the vascular systems communicate with each other in order to give rise to a fully functional and mature CNS. The initial avascular CNS becomes vascularized by blood vessel sprouting from different vascular plexus in a highly stereotypical and controlled manner. This process is similar across different regions of the CNS. In particular for the developing spinal cord (SC), blood vessel ingression occurs from a perineural vascular plexus during embryonic development. In this review, we provide an updated and comprehensive description of the cellular and molecular mechanisms behind this stereotypical and controlled patterning of blood vessels in the developing embryonic SC, identified using different animal models. We discuss how signals derived from neural progenitors and differentiated neurons guide the SC growing vasculature. Lastly, we provide a perspective of how the molecular mechanisms identified during development could be used to better understand pathological situations.

The X-Linked Intellectual Disability Gene Zdhhc9 Is Essential for Dendrite Outgrowth and Inhibitory Synapse Formation.

Palmitoylation is a reversible post-translational lipid modification that facilitates vesicular transport and subcellular localization of modified proteins. This process is catalyzed by ZDHHC enzymes that are implicated in several neurological and neurodevelopmental disorders. Loss-of-function mutations in ZDHHC9 have been identified in patients with X-linked intellectual disability (XLID) and associated with increased epilepsy risk. Loss of Zdhhc9 function in hippocampal cultures leads to shorter dendritic arbors and fewer inhibitory synapses, altering the ratio of excitatory-to-inhibitory inputs formed onto Zdhhc9-deficient cells. While Zdhhc9 promotes dendrite outgrowth through the palmitoylation of the GTPase Ras, it promotes inhibitory synapse formation through the palmitoylation of another GTPase, TC10. Zdhhc9 knockout mice exhibit seizure-like activity together with increased frequency and amplitude of both spontaneous and miniature excitatory and inhibitory postsynaptic currents. These findings present a plausible mechanism for how the loss of ZDHHC9 function may contribute to XLID and epilepsy.

Regulation of dendrite morphology and excitatory synapse formation by zDHHC15.

Protein palmitoylation is the most common post-translational lipid modification in the brain and is mediated by a family of 24 zDHHC enzymes. There has been growing interest in zDHHCs due to mounting evidence that these enzymes play key roles in the development and function of neuronal connections, and the fact that a number of zDHHCs have been associated with neurodevelopmental and neurodegenerative diseases. Loss-of-function variants in several zDHHCs, including zDHHC15, have been identified in patients with intellectual disabilities; however, the function of zDHHC15 in the brain has not been well studied. Here, we demonstrate that knocking down zDHHC15 in primary rat hippocampal cultures reduces dendritic outgrowth and arborization, as well as spine maturation. Moreover, knockdown of zDHHC15 reduces palmitoylation of PSD-95 and its trafficking into dendrites, resulting in an overall decrease in the density of excitatory synapses being formed onto mutant cells.

Blood Vessels as Regulators of Neural Stem Cell Properties.

In the central nervous system (CNS), a precise communication between the vascular and neural compartments is essential for proper development and function. Recent studies demonstrate that certain neuronal populations secrete various molecular cues to regulate blood vessel growth and patterning in the spinal cord and brain during development. Interestingly, the vasculature is now emerging as a critical component that regulates stem cell niches during neocortical development, as well as during adulthood. In this review article, we will first provide an overview of blood vessel development and maintenance in embryonic and adult neurogenic niches. We will also summarize the current understanding of how blood vessel-derived signals influence the behavior of neural stem cells (NSCs) during early development as well as in adulthood, with a focus on their metabolism.

Short-term Intensive Immunosuppression: A Randomized, Three-arm Study of Intravenous Pulse Methylprednisolone and Cyclophosphamide in Macular Serpiginous Choroiditis.

PURPOSE: To compare the efficacy of pulse cyclophosphamide with pulse dexamethasone in acute macular serpiginous choroiditis (SC). METHODS: A total of 30 patients with macular SC were prospectively randomized into three treatment groups: group D (pulse dexamethasone); group C (pulse cyclophosphamide); and combination (pulse group DCP) administered for 3 days. Macular SC was defined as any active lesion involving/threatening macula. RESULTS: A total of 30 patients were enrolled, with 10 patients in each group. Lesions completely healed at median duration of 2 weeks in each group, with significant improvement in visual acuity compared with pretreatment levels (p<0.05). Pulse cyclophosphamide was most effective in faster healing of lesions compared with other groups. There was no difference in gain in visual acuity between any of the groups (p = 0.32). CONCLUSIONS: Cyclophosphamide may be an effective treatment modality for acute macular SC, though it may not have a long-term effect on disease relapse.

Surprises during intravitreal drug delivery-a report of three cases.

We describe 3 cases with unusual events during and after intravitreal injection of dexamethasone intravitreal implants and bevacizumab. In case 1, delayed release of the safety stop of a dexamethasone intravitreal implant injector led to impaction and retinal break formation. Timely recognition and laser treatment prevented further retinal complications. In case 2, reinjection of a second dexamethasone intravitreal implant from the same site as the first injection was noted to dislodge the remnant of the previous implant from the vitreous base. In case 3, translucent floating particles were noted in the vitreous after intravitreal injection of bevacizumab from ampules procured from our dispensing pharmacy.

Rap1 GTPases Are Master Regulators of Neural Cell Polarity in the Developing Neocortex.

During the development of the mammalian neocortex, the generation of neurons by neural progenitors and their migration to the final position are closely coordinated. The highly polarized radial glial cells (RGCs) serve both as progenitor cells to generate neurons and as support for the migration of these neurons. After their generation, neurons transiently assume a multipolar morphology before they polarize and begin their migration along the RGCs. Here, we show that Rap1 GTPases perform essential functions for cortical organization as master regulators of cell polarity. Conditional deletion of Rap1 GTPases leads to a complete loss of cortical lamination. In RGCs, Rap1 GTPases are required to maintain their polarized organization. In newborn neurons, the loss of Rap1 GTPases prevents the formation of axons and leading processes and thereby interferes with radial migration. Taken together, the loss of RGC and neuronal polarity results in the disruption of cortical organization.

Influence of Sterilization Technologies on Electrospun Poly(ester urea)s for Soft Tissue Repair.

Degradable poly(ester urea)s (PEU)s were electrospun into nanofiber sheets and assessed for their potential to be used in soft tissue repair. The level of residual solvent was measured and the effects of ethylene oxide and electron beam sterilization techniques on molecular mass, mass distribution, and morphology were quantified. Two PEU compositions that formed stable nanofiber sheets were advanced into a pilot study in vitro and in vivo as candidate materials for hernia repair. Cell viability, spreading, proliferation, and migration were examined in vitro. Nanofiber sheets were implanted subcutaneously into mice and analyzed via microangiography and histology for tissue incorporation. Nanofiber sheets performed similarly to decellularized extracellular matrix (ECM) in vitro, but the lack of sufficient pore structure inhibited cellular infiltration after 14 days of culture. The lack of microporous features in nanofiber sheets also contributed to low levels of cellular infiltration, angiogenesis, and matrix deposition in vivo. A preliminary study to increase pore size in nanofibers was performed using coaxial electrospinning resulting in significant improvement in tissue infiltration in vivo.

Regulation of Rap GTPases in mammalian neurons.

Small GTPases are central regulators of many cellular processes. The highly conserved Rap GTPases perform essential functions in the mammalian nervous system during development and in mature neurons. During neocortical development, Rap1 is required to regulate cadherin- and integrin-mediated adhesion. In the adult nervous system Rap1 and Rap2 regulate the maturation and plasticity of dendritic spine and synapses. Although genetic studies have revealed important roles of Rap GTPases in neurons, their regulation by guanine nucleotide exchange factors (GEFs) that activate them and GTPase activating proteins (GAPs) that inactivate them by stimulating their intrinsic GTPase activity is just beginning to be explored in vivo. Here we review how GEFs and GAPs regulate Rap GTPases in the nervous system with a focus on their in vivo function.