RHOJ controls EMT-associated resistance to chemotherapy.

The resistance of cancer cells to therapy is responsible for the death of most patients with cancer1. Epithelial-to-mesenchymal transition (EMT) has been associated with resistance to therapy in different cancer cells2,3. However, the mechanisms by which EMT mediates resistance to therapy remain poorly understood. Here, using a mouse model of skin squamous cell carcinoma undergoing spontaneous EMT during tumorigenesis, we found that EMT tumour cells are highly resistant to a wide range of anti-cancer therapies both in vivo and in vitro. Using gain and loss of function studies in vitro and in vivo, we found that RHOJ-a small GTPase that is preferentially expressed in EMT cancer cells-controls resistance to therapy. Using genome-wide transcriptomic and proteomic profiling, we found that RHOJ regulates EMT-associated resistance to chemotherapy by enhancing the response to replicative stress and activating the DNA-damage response, enabling tumour cells to rapidly repair DNA lesions induced by chemotherapy. RHOJ interacts with proteins that regulate nuclear actin, and inhibition of actin polymerization sensitizes EMT tumour cells to chemotherapy-induced cell death in a RHOJ-dependent manner. Together, our study uncovers the role and the mechanisms through which RHOJ acts as a key regulator of EMT-associated resistance to chemotherapy.

RhoJ integrates attractive and repulsive cues in directional migration of endothelial cells.

During angiogenesis, VEGF acts as an attractive cue for endothelial cells (ECs), while Sema3E mediates repulsive cues. Here, we show that the small GTPase RhoJ integrates these opposing signals in directional EC migration. In the GTP-bound state, RhoJ interacts with the cytoplasmic domain of PlexinD1. Upon Sema3E stimulation, RhoJ released from PlexinD1 induces cell contraction. PlexinD1-bound RhoJ further facilitates Sema3E-induced PlexinD1-VEGFR2 association, VEGFR2 transphosphorylation at Y1214, and p38 MAPK activation, leading to reverse EC migration. Upon VEGF stimulation, RhoJ is required for the formation of the holoreceptor complex comprising VEGFR2, PlexinD1, and neuropilin-1, thereby preventing degradation of internalized VEGFR2, prolonging downstream signal transductions via PLCγ, Erk, and Akt, and promoting forward EC migration. After conversion to the GDP-bound state, RhoJ shifts from PlexinD1 to VEGFR2, which then terminates the VEGFR2 signals. RhoJ deficiency in ECs efficiently suppressed aberrant angiogenesis in ischemic retina. These findings suggest that distinct Rho GTPases may act as context-dependent integrators of chemotactic cues in directional cell migration and may serve as candidate therapeutic targets to manipulate cell motility in disease or tissue regeneration.

Embryonic Pericytes Promote Microglial Homeostasis and Their Effects on Neural Progenitors in the Developing Cerebral Cortex.

Multifaceted microglial functions in the developing brain, such as promoting the differentiation of neural progenitors and contributing to the positioning and survival of neurons, have been progressively revealed. Although previous studies have noted the relationship between vascular endothelial cells and microglia in the developing brain, little attention has been given to the importance of pericytes, the mural cells surrounding endothelial cells. In this study, we attempted to dissect the role of pericytes in microglial distribution and function in developing mouse brains. Our immunohistochemical analysis showed that approximately half of the microglia attached to capillaries in the cerebral walls. Notably, a magnified observation of the position of microglia, vascular endothelial cells and pericytes demonstrated that microglia were preferentially associated with pericytes that covered 79.8% of the total capillary surface area. Through in vivo pericyte depletion induced by the intraventricular administration of a neutralizing antibody against platelet-derived growth factor receptor (PDGFR)ß (clone APB5), we found that microglial density was markedly decreased compared with that in control antibody-treated brains because of their low proliferative capacity. Moreover, in vitro coculture of isolated CD11b+ microglia and NG2+PDGFRα- cells, which are mostly composed of pericytes, from parenchymal cells indicated that pericytes promote microglial proliferation via the production of soluble factors. Furthermore, pericyte depletion by APB5 treatment resulted in a failure of microglia to promote the differentiation of neural stem cells into intermediate progenitors. Taken together, our findings suggest that pericytes facilitate microglial homeostasis in the developing brains, thereby indirectly supporting microglial effects on neural progenitors.SIGNIFICANCE STATEMENT This study highlights the novel effect of pericytes on microglia in the developing mouse brain. Through multiple analyses using an in vivo pericyte depletion mouse model and an in vitro coculture study of isolated pericytes and microglia from parenchymal cells, we demonstrated that pericytes contribute to microglial proliferation and support microglia in efficiently promoting the differentiation of neural stem cells into intermediate progenitors. Our present data provide evidence that pericytes function not only in the maintenance of cerebral microcirculation and blood brain barrier (BBB) integrity but also in microglial homeostasis in the developing cerebral walls. These findings will expand our knowledge and help elucidate the mechanism of brain development both in healthy and disease conditions.

Roles of lipocalin-type and hematopoietic prostaglandin D synthases in mouse retinal angiogenesis.

Normal angiogenesis is essential for retinal development and maintenance of visual function in the eye, and its abnormality can cause retinopathy and other eye diseases. Prostaglandin D2 is an anti-angiogenic lipid mediator produced by lipocalin-type PGD synthase (L-PGDS) or hematopoietic PGD synthase (H-PGDS). However, the exact role of these PGD synthases remains unclear. Therefore, we compared the roles of these synthases in murine retinal angiogenesis under physiological and pathological conditions. On postnatal day (P) 8, the WT murine retina was covered with an elongated vessel. L-PGDS deficiency, but not H-PGDS, reduced the physiological vessel elongation with sprouts increase. L-PGDS expression was observed in endothelial cells and neural cells. In vitro, L-PGDS inhibition increased the hypoxia-induced vascular endothelial growth factor expression in isolated endothelial cells, inhibited by a prostaglandin D2 metabolite, 15-deoxy-Δ12,14 -PGJ2 (15d-PGJ2) treatment. Pericyte depletion, using antiplatelet-derived growth factor receptor-ß antibody, caused retinal hemorrhage with vessel elongation impairment and macrophage infiltration in the WT P8 retina. H-PGDS deficiency promoted hemorrhage but inhibited the impairment of vessel elongation, while L-PGDS did not. In the pericyte-depleted WT retina, H-PGDS was expressed in the infiltrated macrophages. Deficiency of the D prostanoid receptor also inhibited the vessel elongation impairment. These results suggest the endogenous role of L-PGDS signaling in physiological angiogenesis and that of H-PGDS/D prostanoid 1 signaling in pathological angiogenesis.

Effect of triamcinolone acetonide on retinal inflammation and angiogenesis induced by pericyte depletion in mouse.

Triamcinolone acetonide (TA) has been shown to improve morphological and functional outcome in diabetic macular edema (DME) patients. However, the functional mechanism of TA has not been elucidated yet. In this study we investigated the detailed functional mechanism of TA using culture cells and retinopathy mouse models in which retinal inflammation and abnormal angiogenesis were induced by pericyte depletion. TA significantly prevented retinal hemorrhage, edema and partially improved abnormal angiogenesis. TA decreased retinal vascular endothelial growth factor (VEGF) concentration, presumably by preventing recruitment of macrophages into retina and TA also inhibited expression of inflammatory cytokines in retina. TA inhibited proliferation/migration of vascular endothelial cells and vessel sprouting. No direct inhibition of VEGF receptor 2 (VEGFR2) autophosphorylation was observed by TA. These results suggested that TA improved inflammatory retinal events which were induced in pericyte-deleted mice by mainly decreasing macrophage-derived VEGF and expression of inflammatory cytokines followed by attenuation of vascular permeability and proliferation/migration of endothelial cells. Furthermore, in these processes, translocation of glucocorticoid receptor (GR) was partially involved.

PlexinD1 signaling controls morphological changes and migration termination in newborn neurons.

Newborn neurons maintain a very simple, bipolar shape, while they migrate from their birthplace toward their destinations in the brain, where they differentiate into mature neurons with complex dendritic morphologies. Here, we report a mechanism by which the termination of neuronal migration is maintained in the postnatal olfactory bulb (OB). During neuronal deceleration in the OB, newborn neurons transiently extend a protrusion from the proximal part of their leading process in the resting phase, which we refer to as a filopodium-like lateral protrusion (FLP). The FLP formation is induced by PlexinD1 downregulation and local Rac1 activation, which coincide with microtubule reorganization and the pausing of somal translocation. The somal translocation of resting neurons is suppressed by microtubule polymerization within the FLP The timing of neuronal migration termination, controlled by Sema3E-PlexinD1-Rac1 signaling, influences the final positioning, dendritic patterns, and functions of the neurons in the OB These results suggest that PlexinD1 signaling controls FLP formation and the termination of neuronal migration through a precise control of microtubule dynamics.

Dll4 Suppresses Transcytosis for Arterial Blood-Retinal Barrier Homeostasis.

RATIONALE: Central nervous system has low vascular permeability by organizing tight junction (TJ) and limiting endothelial transcytosis. While TJ has long been considered to be responsible for vascular barrier in central nervous system, suppressed transcytosis in endothelial cells is now emerging as a complementary mechanism. Whether transcytosis regulation is independent of TJ and its dysregulation dominantly causes diseases associated with edema remain elusive. Dll4 signaling is important for various vascular contexts, but its role in the maintenance of vascular barrier in central nervous system remains unknown. OBJECTIVE: To find a TJ-independent regulatory mechanism selective for transcytosis and identify its dysregulation as a cause of pathological leakage. METHODS AND RESULTS: We studied transcytosis in the adult mouse retina with low vascular permeability and employed a hypertension-induced retinal edema model for its pathological implication. Both antibody-based and genetic inactivation of Dll4 or Notch1 induce hyperpermeability by increasing transcytosis without junctional destabilization in arterial endothelial cells, leading to nonhemorrhagic leakage predominantly in the superficial retinal layer. Endothelial Sox17 deletion represses Dll4 in retinal arteries, phenocopying Dll4 blocking-driven vascular leakage. Ang II (angiotensin II)-induced hypertension represses arterial Sox17 and Dll4, followed by transcytosis-driven retinal edema, which is rescued by a gain of Notch activity. Transcriptomic profiling of retinal endothelial cells suggests that Dll4 blocking activates SREBP1 (sterol regulatory element-binding protein 1)-mediated lipogenic transcription and enriches gene sets favorable for caveolae formation. Profiling also predicts the activation of VEGF (vascular endothelial growth factor) signaling by Dll4 blockade. Inhibition of SREBP1 or VEGF-VEGFR2 (VEGF receptor 2) signaling attenuates both Dll4 blockade-driven and hypertension-induced retinal leakage. CONCLUSIONS: In the retina, Sox17-Dll4-SREBP1 signaling axis controls transcytosis independently of TJ in superficial arteries among heterogeneous regulations for the whole vessels. Uncontrolled transcytosis via dysregulated Dll4 underlies pathological leakage in hypertensive retina and could be a therapeutic target for treating hypertension-associated retinal edema.

Loss of Down Syndrome Critical Region-1 Mediated-Hypercholesterolemia Accelerates Corneal Opacity Via Pathological Neovessel Formation.

OBJECTIVE: The calcineurin-NFAT (nuclear factor for activated T cells)-DSCR (Down syndrome critical region)-1 pathway plays a crucial role as the downstream effector of VEGF (vascular endothelial growth factor)-mediated tumor angiogenesis in endothelial cells. A role for DSCR-1 in different organ microenvironment such as the cornea and its role in ocular diseases is not well understood. Corneal changes can be indicators of various disease states and are easily detected through ocular examinations. Approach and Results: The presentation of a corneal arcus or a corneal opacity due to lipid deposition in the cornea often indicates hyperlipidemia and in most cases, hypercholesterolemia. Although the loss of Apo (apolipoprotein) E has been well characterized and is known to lead to elevated serum cholesterol levels, there are few corneal changes observed in ApoE-/- mice. In this study, we show that the combined loss of ApoE and DSCR-1 leads to a dramatic increase in serum cholesterol levels and severe corneal opacity with complete penetrance. The cornea is normally maintained in an avascular state; however, loss of Dscr-1 is sufficient to induce hyper-inflammatory and -oxidative condition, increased corneal neovascularization, and lymphangiogenesis. Furthermore, immunohistological analysis and genome-wide screening revealed that loss of Dscr-1 in mice triggers increased immune cell infiltration and upregulation of SDF (stromal derived factor)-1 and its receptor, CXCR4 (C-X-C motif chemokine ligand receptor-4), potentiating this signaling axis in the cornea, thereby contributing to pathological corneal angiogenesis and opacity. CONCLUSIONS: This study is the first demonstration of the critical role for the endogenous inhibitor of calcineurin, DSCR-1, and pathological corneal angiogenesis in hypercholesterolemia induced corneal opacity.

Rho GTPases in Retinal Vascular Diseases.

The Rho family of small GTPases (Rho GTPases) act as molecular switches that transduce extrinsic stimuli into cytoskeletal rearrangements. In vascular endothelial cells (ECs), Cdc42, Rac1, and RhoA control cell migration and cell-cell junctions downstream of angiogenic and inflammatory cytokines, thereby regulating vascular formation and permeability. While these Rho GTPases are broadly expressed in various types of cells, RhoJ is enriched in angiogenic ECs. Semaphorin 3E (Sema3E) releases RhoJ from the intracellular domain of PlexinD1, by which RhoJ induces actin depolymerization through competition with Cdc42 for their common effector proteins. RhoJ further mediates the Sema3E-induced association of PlexinD1 with vascular endothelial growth factor receptor (VEGFR) 2 and the activation of p38. Upon stimulation with VEGF-A, RhoJ facilitates the formation of a holoreceptor complex comprising VEGFR2, PlexinD1, and neuropilin-1, leading to the prevention of VEGFR2 degradation and the maintenance of intracellular signal transduction. These pleiotropic roles of RhoJ are required for directional EC migration in retinal angiogenesis. This review highlights the latest insights regarding Rho GTPases in the field of vascular biology, as it will be informative to consider their potential as targets for the treatment of aberrant angiogenesis and hyperpermeability in retinal vascular diseases.

Endosomal sorting by Semaphorin 4A in retinal pigment epithelium supports photoreceptor survival.

Photoreceptor cell death is the hallmark of a group of human inherited retinal degeneration. Although the causative genetic mutations are often known, the mechanisms leading to photoreceptor degeneration remain poorly defined. Here, we show that Semaphorin 4A (Sema4A), a member of axonal guidance molecule semaphorin, plays a role in Rab11/FIP2-mediated endosomal sorting in retinal pigment epithelial cells to support photoreceptor function. In response to oxidative stress, Sema4A switches the endosomal sorting of the lysosomal precursor protein prosaposin from the lysosome to the exosomal release, which prevents light-induced photoreceptor apoptosis. In the absence of oxidative stress, Sema4A sorts retinoid-binding proteins with retinoids between the cell surface and endoplasmic reticulum, by which 11-cis-retinal, a chromophore for phototransduction, is regenerated and transported back to photoreceptors. Owing to defects in these processes, Sema4A-deficient mice exhibit marked photoreceptor degeneration. Our findings therefore indicate that Sema4A regulates two distinct endosomal-sorting pathways that are critical for photoreceptor survival and phototransduction during the transition between daylight and darkness.

Structural and Functional Analyses of Retinal Ischemia in Eyes with Retinal Vein Occlusion: Relationship with Macular Edema or Microaneurysm Formation.

PURPOSE: To study the structural and functional changes of retinal ischemia and investigate their association with macular edema (ME) or microaneurysm (MA) formation in eyes with retinal vein occlusion (RVO). METHODS: Sixty eyes of 30 patients (27 eyes with branch [b]RVO, 3 with central RVO, and 30 fellow eyes) were retrospectively reviewed. Optical coherence tomography (OCT), OCT angiography (OCTA), and microperimetry were performed simultaneously to measure retinal thickness and sensitivity. The presence of ME or MA was also assessed using OCT and fluorescein angiography. RESULTS: The mean retinal sensitivity in the nonperfused areas (NPAs) deteriorated, and this was significantly (r = -0.379, p = 0.0391*) and inversely correlated with duration from disease onset. ME and MA were unlikely to be observed around the area where the retinal sensitivity decreased. In the NPAs, the mean retinal thickness of the superficial capillary plexus (SCP) (p < 0.0001), deep capillary plexus (DCP) (p = 0.0323), and outer retina (p = 0.0008) were significantly thinner than those in the fellow eyes, respectively. Multivariate regression analysis revealed that the thicknesses of the DCP (ß: 0.3107, p = 0.0007) and outer retina (ß: 0.3482, p = 0.0001) were the independent correlative factors of the retinal sensitivity, but that SCP thickness was not. CONCLUSION: Deep retinal thinning in NPAs was correlated significantly with a decreased retinal sensitivity, which might be a negative predictor of ME and MA in eyes with RVO.

A sodium-glucose cotransporter 2 inhibitor attenuates renal capillary injury and fibrosis by a vascular endothelial growth factor-dependent pathway after renal injury in mice.

Multiple large clinical trials have shown that sodium-glucose cotransporter (SGLT) 2 inhibitors reduce the risk of renal events. However, the mechanism responsible for this outcome remains unknown. Here we investigated the effects of the SGLT2 inhibitor luseogliflozin on the development of renal fibrosis after renal ischemia/reperfusion injury in non-diabetic mice. Luseogliflozin significantly suppressed development of renal fibrosis, prevented peritubular capillary congestion/hemorrhage, attenuated CD31-positive cell loss, suppressed hypoxia, and increased vascular endothelial growth factor (VEGF)-A expression in the kidney after ischemia/reperfusion injury. Luseogliflozin failed to induce the above-mentioned protection in animals co-treated with sunitinib, a VEGF receptor inhibitor. Additionally, luseogliflozin reduced glucose uptake and increased VEGF-A expression in the kidneys of glucose transporter 2 (GLUT2)-downregulated mice following ischemia/reperfusion and in GLUT2-knock-down cells compared with those in normal controls. Withdrawal of glucose from cultured medium, to halt glucose uptake, remarkably increased VEGF-A expression and reversed the luseogliflozin-induced increase in VEGF-A expression in the proximal tubular cells. Thus, luseogliflozin prevented endothelial rarefaction and subsequent renal fibrosis after renal ischemia/reperfusion injury through a VEGF-dependent pathway induced by the dysfunction of proximal tubular glucose uptake in tubules with injury-induced GLUT2 downregulation.

Flattening of retinal pigment epithelial detachments after pneumatic displacement of submacular hemorrhages secondary to age-related macular degeneration.

PURPOSE: Pneumatic displacement of submacular hemorrhages (SMHs) with intravitreal injection of sulfur hexafluoride (SF6) gas with or without tissue plasminogen activator (tPA) and prone posturing is an effective minimally invasive treatment. We observed some cases in which simultaneous flattening of hemorrhagic pigment epithelial detachments (PEDs) occurred after prone posturing. This study evaluated the impact of pneumatic displacement using tPA to treat PEDs and visual outcomes in eyes with SMHs secondary to neovascular age-related macular degeneration (AMD). METHODS: This retrospective analysis reviewed the medical records of 32 patients (33 eyes) who underwent pneumatic displacement for AMD-associated SMHs. The SMHs were related to polypoidal choroidal vasculopathy (PCV) in 24 eyes and typical AMD in nine eyes and treated with intravitreal injection of SF6 gas with tPA. We assessed the postoperative best-corrected visual acuities (BCVAs), prevalence and flattening rates of the PEDs, and the number of additional treatments. RESULTS: The mean follow-up period was 35.4 ± 19.8 months. The BCVAs improved significantly in eyes with PCV compared with eyes with typical AMD. Thirty-one (93.9%) of 33 eyes had an accompanying PED. The PEDs flattened in 14 (58.3%) of 24 eyes with PCV but in only one (14.3%) of seven eyes with typical AMD (p = 0.04). A mean of one additional treatment was administered during the first year in 15 eyes with flattened PEDs, which was significantly (p < 0.05) fewer than the 3.6 additional treatments in 16 eyes with persistent PEDs. CONCLUSIONS: PEDs often accompany SMHs secondary to neovascular AMD. Pneumatic displacement of the SMHs using tPA unexpectedly flattened the PEDs, especially in eyes with PCV, and was associated with fewer additional treatments.

Indocyanine Green Angiography-Guided Focal Laser Photocoagulation for Diabetic Macular Edema.

PURPOSE: To evaluate the usefulness of indocyanine green angiography (ICGA) to detect leaking spots and the effectiveness of ICGA-guided focal laser photocoagulation in eyes with diabetic macular edema (DME). METHODS: Ten eyes (8 patients) with diffuse DME diagnosed using fluorescein angiography (FA) and refractory to a sub-Tenon injection of triamcinolone acetonide (STTA), grid laser photocoagulation, or both were enrolled. FA and ICGA were performed using the Heidelberg Retina Angiograph 2. Hyperfluorescent spots on early-phase FA and on early- and late-phase ICGA were superimposed onto the macular thickness map measured by optical coherence tomography (OCT) and counted to calculate the spot density in the area with or without macular edema (ME). ICGA-guided focal laser photocoagulation was carried out. In 7 eyes, STTA was simultaneously performed. The central macular thickness (CRT) and macular volume (MV) were measured by OCT. RESULTS: On early-phase FA, 4.8 ± 2.3 and 2.3 ± 1.5 hyperfluorescent spots/disk area were observed inside and outside the ME, respectively. In contrast, the spot density was significantly decreased to 1.8 ± 0.9 inside the ME and was only 0.3 ± 0.4 outside the ME on late-phase ICGA (p < 0.01). The mean follow-up period after ICGA-guided photocoagulation was 19.0 months. The mean best-corrected visual acuity improved significantly from 0.77 ± 0.34 logarithm of the minimum angle of resolution at baseline to 0.52 ± 0.37 at the last visit (p < 0.01). Both CRT and MV significantly decreased (p < 0.01). Recurrence of DME was observed in 4 eyes: 3 eyes were treatable only with STTA and 1 required additional ICGA-guided laser photocoagulation. CONCLUSIONS: ICGA may be useful to detect leaking spots responsible for DME, enabling less invasive focal laser photocoagulation even in some of the eyes with diffuse DME.

FOXO1 stimulates tip cell-enriched gene expression in endothelial cells.

Forkhead box O (FOXO) family proteins are expressed in various cells, and play crucial roles in cellular metabolism, apoptosis, and aging. FOXO1-null mice exhibit embryonic lethality due to impaired endothelial cell (EC) maturation and vascular remodeling. However, FOXO1-mediated genome-wide regulation in ECs remains unclear. Here, we demonstrate that VEGF dynamically regulates FOXO1 cytosol-nucleus translocation. FOXO1 re-localizes to the nucleus via PP2A phosphatase. RNA-seq combined with FOXO1 overexpression/knockdown in ECs demonstrated that FOXO1 governs the VEGF-responsive tip cell-enriched genes, and further inhibits DLL4-NOTCH signaling. Endogenous FOXO1 ChIP-seq revealed that FOXO1 binds to the EC-unique tip-enriched genes with co-enrichment of EC master regulators, and the condensed chromatin region as a pioneer factor. We identified new promoter/enhancer regions of the VEGF-responsive tip cell genes regulated by FOXO1: ESM1 and ANGPT2. This is the first study to identify cell type-specific FOXO1 functions, including VEGF-mediated tip cell definition in primary cultured ECs.

Targeting the Mitochondrial Chaperone TRAP1 Alleviates Vascular Pathologies in Ischemic Retinopathy.

Activation of hypoxia-inducible factor 1α (HIF1α) contributes to blood-retinal barrier (BRB) breakdown and pathological neovascularization responsible for vision loss in ischemic retinal diseases. During disease progression, mitochondrial biology is altered to adapt to the ischemic environment created by initial vascular dysfunction, but the mitochondrial adaptive mechanisms, which ultimately contribute to the pathogenesis of ischemic retinopathy, remain incompletely understood. In the present study, it is identified that expression of mitochondrial chaperone tumor necrosis factor receptor-associated protein 1 (TRAP1) is essential for BRB breakdown and pathologic retinal neovascularization in mouse models mimicking ischemic retinopathies. Genetic Trap1 ablation or treatment with small molecule TRAP1 inhibitors, such as mitoquinone (MitoQ) and SB-U015, alleviate retinal pathologies via proteolytic HIF1α degradation, which is mediated by opening of the mitochondrial permeability transition pore and activation of calcium-dependent protease calpain-1. These findings suggest that TRAP1 can be a promising target for the development of new treatments against ischemic retinopathy, such as retinopathy of prematurity and proliferative diabetic retinopathy.

Reduced chondroitin sulfate content prevents diabetic neuropathy through transforming growth factor-ß signaling suppression.

Diabetic neuropathy (DN) is a major complication of diabetes mellitus. Chondroitin sulfate (CS) is one of the most important extracellular matrix components and is known to interact with various diffusible factors; however, its role in DN pathology has not been examined. Therefore, we generated CSGalNAc-T1 knockout (T1KO) mice, in which CS levels were reduced. We demonstrated that diabetic T1KO mice were much more resistant to DN than diabetic wild-type (WT) mice. We also found that interactions between pericytes and vascular endothelial cells were more stable in T1KO mice. Among the RNA-seq results, we focused on the transforming growth factor ß signaling pathway and found that the phosphorylation of Smad2/3 was less upregulated in T1KO mice than in WT mice under hyperglycemic conditions. Taken together, a reduction in CS level attenuates DN progression, indicating that CS is an important factor in DN pathogenesis.

FGD5 mediates proangiogenic action of vascular endothelial growth factor in human vascular endothelial cells.

OBJECTIVE: Vascular endothelial growth factor (VEGF) exerts proangiogenic action and induces activation of a variety of proangiogenic signaling pathways, including the Rho family small G proteins. However, regulators of the Rho family small G proteins in vascular endothelial cells (ECs) are poorly understood. Here we attempted to clarify the expression, subcellular localization, downstream effectors, and proangiogenic role of FGD5, a member of the FGD family of guanine nucleotide exchange factors. METHODS AND RESULTS: FGD5 was shown to be selectively expressed in cultured human vascular ECs. Immunofluorescence microscopy showed that the signal for FGD5 was observed at peripheral membrane ruffles and perinuclear regions in human umbilical vein ECs. Overexpression of FGD5 increased Cdc42 activity, whereas knockdown of FGD5 by small interfering RNAs inhibited the VEGF-induced activation of Cdc42 and extracellular signal-regulated kinase. VEGF-promoted capillary-like network formation, permeability, directional movement, and proliferation of human umbilical vein ECs and the reorientation of the Golgi complex during directional cell movement were attenuated by knockdown of FGD5. CONCLUSIONS: This study provides the first demonstration of expression, subcellular localization, and function of FGD5 in vascular ECs. The results suggest that FGD5 regulates proangiogenic action of VEGF in vascular ECs, including network formation, permeability, directional movement, and proliferation.

PlexinD1 signaling controls domain-specific dendritic development in newborn neurons in the postnatal olfactory bulb.

Newborn neurons show immature bipolar morphology and continue to migrate toward their destinations. After the termination of migration, newborn neurons undergo spatially controlled dendrite formation and change into a complex morphology. The mechanisms of dendritic development of newborn neurons have not been fully understood. Here, we show that in the postnatal olfactory bulb (OB), the Sema3E-PlexinD1 signaling, which maintains bipolar morphology of newborn neurons, also regulates their dendritic development after the termination of migration in a dendritic domain-specific manner. Genetic ablation of Sema3E or PlexinD1 enhanced dendritic branching in the proximal domain of the apical dendrites of OB newborn granule cells, whereas PlexinD1 overexpression suppressed it in a Rho binding domain (RBD)-dependent manner. Furthermore, RhoJ, a small GTPase that directly binds to PlexinD1RBD in vascular endothelial cells, is expressed in migrating and differentiating newborn granule cells in the OB and is also involved in the suppression of proximal branching of their apical dendrites. These results suggest that the Sema3E-PlexinD1-RhoJ axis regulates domain-specific dendrite formation of newborn neurons in the postnatal OB.

Corrigendum: PlexinD1 signaling controls domain-specific dendritic development in newborn neurons in the postnatal olfactory bulb.

[This corrects the article DOI: 10.3389/fnins.2023.1143130.].