Role of the ß2-adrenergic receptor in podocyte injury and recovery.

BACKGROUND: Podocytes have a remarkable ability to recover from injury; however, little is known about the recovery mechanisms involved in this process. We recently showed that formoterol, a long-acting ß2-adrenergic receptor (ß2-AR) agonist, induced mitochondrial biogenesis (MB) in podocytes and led to renoprotection in mice. However, it is not clear whether this effect was mediated by formoterol acting through the ß2-AR or if it occurred through "off-target" effects. METHODS: We genetically deleted the ß2-AR specifically in murine podocytes and used these mice to determine whether formoterol acting through the podocyte ß2-AR alone is sufficient for recovery of renal filtration function following injury. The podocyte-specific ß2-AR knockout mice (ß2-ARfl/fl/PodCre) were generated by crossing ß2-AR floxed mice with podocin Cre (B6.Cg-Tg(NPHS2-cre)295Lbh/J) mice. These mice were then subjected to both acute and chronic glomerular injury using nephrotoxic serum (NTS) and adriamycin (ADR), respectively. The extent of injury was evaluated by measuring albuminuria and histological and immunostaining analysis of the murine kidney sections. RESULTS: A similar level of injury was observed in ß2-AR knockout and control mice; however, the ß2-ARfl/fl/PodCre mice failed to recover in response to formoterol. Functional evaluation of the ß2-ARfl/fl/PodCre mice following injury plus formoterol showed similar albuminuria and glomerular injury to control mice that were not treated with formoterol. CONCLUSIONS: These results indicate that the podocyte ß2-AR is a critical component of the recovery mechanism and may serve as a novel therapeutic target for treating podocytopathies.

Double Mesiodens in the Mixed Dentition of Non-syndromic North-Indian Patients: A Case Series.

The presence of double mesiodens or mesiodentes, i.e., two supernumerary teeth in the maxillary midline, presents unique challenges in mixed dentition. Common clinical manifestations include delayed eruption, midline diastema, and occlusal disturbances, leading to complications such as root resorption, pathological migration of tooth, crowding, cyst formation, and malocclusion. Mesiodens can be associated with several syndromes, like cleidocranial dysplasia, familial adenomatous polyposis, trichorhinophalangeal syndrome, type I, Rubinstein-Taybi syndrome, and Nance-Horan syndrome, among others. It can also be secondary to trauma, hyperactivity of the dental lamina, and a combination of genetic and environmental factors, but its etiology continues to be idiopathic. Double mesiodens are relatively rare, so this clinical observation aimed to highlight five such cases of double mesiodens in mixed dentition in non-syndromic children and adolescents. Additionally, a literature search reporting cases of double mesiodens in the mixed dentition was done, and the results were tabulated. Clinicians should be able to identify indications of supernumerary teeth, specifically deviations in the eruption pattern. Appropriate investigations and timely intervention are essential to reducing complications that may arise in the developing dentition.

Frustration responses of single and partnered mothers to prolonged infant crying.

Prolonged infant crying can be a trigger for maternal frustration and can even predict intrusive infant-related thoughts of harm. In this study, we compared frustration responses to prolonged infant crying between single and partnered mothers and attempted to identify variables that mediated any difference between the two groups. We also identified acoustic characteristics of infant cries that were related to higher levels of reported maternal frustration. Twenty-five single and 25 partnered mothers with infants under the age of 6 months completed several mental health questionnaires, and then rated their frustration level after listening to each of 50 consecutive 15s infant cry videos from 50 different infants. As expected, greater maternal perceived stress was associated with higher frustration ratings in response to infant crying, and this was mediated by increased maternal negative affect. Also as expected, both financial strain and low social support were associated with greater perceived stress. However, our sample of single mothers did not experience more stress than our sample of partnered mothers. Nor did they find infant crying to be more frustrating, perhaps due to a recruitment bias toward higher functioning single mothers. Finally, several cry acoustic characteristics were associated with increased maternal frustration, including higher fundamental frequency, air energy, shimmer and longer duration of expiratory phonations, as well as a longer cumulative duration of crying. Our results suggest that maternal frustration in response to infant crying may be decreased by lowering maternal stress levels, and this may be achieved by increasing social support and decreasing financial strain. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Oral submucous fibrosis and its impact on psychological stress: a case-control study.

Our aim was to evaluate the impact of OSF on psychological stress. Ninety OSF cases and age and sex-matched controls, enrolled from relatives or accompanying person were included in the study. Psychological stress was evaluated by the Psychological General Well Being Index short version (PGWBI-S). Sets of the psychological component were generated by principal component analysis (PCA). Association between components was accommodated for confounder and interaction was evaluated by conditional stepwise logistic regression analysis. Psychological component generated was component 1 (depressed mood, lack of positive well being, low vitality, anxiety, low vitality, and low self-control). The odds ratio (OR) of low score of component 1 for OSF was 3.66. Depressed mood, lack of positive well being, low vitality, anxiety, low vitality, and low self-control were associated with OSF. Psychological intervention should, therefore, be included in the management of OSF.

Impact of COVID-19 on presentation, staging, and treatment of head and neck mucosal squamous cell carcinoma.

OBJECTIVES: During the COVID-19 pandemic, maintenance of safe and timely oncologic care has been challenging. The goal of this study is to compare presenting symptoms, staging, and treatment of head and neck mucosal squamous cell carcinoma during the pandemic with an analogous timeframe one year prior. MATERIALS AND METHODS: Retrospective cohort study at a single tertiary academic center of new adult patients evaluated in a head and neck surgical oncology clinic from March -July 2019 (pre-pandemic control) and March - July 2020 (COVID-19 pandemic). RESULTS: During the pandemic, the proportion of patients with newly diagnosed malignancies increased by 5%, while the overall number of new patients decreased (n = 575) compared to the control year (n = 776). For patients with mucosal squamous cell carcinoma (SCC), median time from referral to initial clinic visit decreased from 11 days (2019) to 8 days (2020) (p = 0.0031). There was no significant difference in total number (p = 0.914) or duration (p = 0.872) of symptoms. During the pandemic, patients were more likely to present with regional nodal metastases (adjusted odds ratio (OR) 2.846, 95% CI 1.072-3.219, p = 0.028) and more advanced clinical nodal (N) staging (p = 0.011). No significant difference was seen for clinical tumor (T) (p = 0.502) or metastasis (M) staging (p = 0.278). No significant difference in pathologic T (p = 0.665), or N staging (p = 0.907) was found between the two periods. CONCLUSION: Head and neck mucosal SCC patients presented with more advanced clinical nodal disease during the early months of the COVID-19 pandemic despite no change in presenting symptoms.

The prevalence of oral squamous cell carcinoma with oral submucous fibrosis.

OBJECTIVE: The objective of the study was to find out the prevalence of oral squamous cell carcinoma (OSCC) with oral submucous fibrosis (OSF) in patients with OSF. MATERIALS AND METHODS: Of 48,757 patients, we found 300 OSF subjects. Three hundred patients of OSF were checked for OSCC. Both OSF and OSCC with OSF (OSCCwOSF) were diagnosed histopathologically. The prevalence of OSCCwOSF was calculated. Descriptive analysis was done. Chi-square test and t-test were calculated for proportions and mean, respectively, to check any difference among OSF and OSCCwOSF groups. Age-specific relative risk was calculated in OSF and OSCCwOSF groups. Multiple logistic regression analysis was done among odd ratios of the different variable between OSF and OSCCwOSF groups. RESULTS: The prevalence of OSCCwOSF among OSF was 13.7% over a period of 1 year. The mean age of OSCCwOSF group was 43.95 ± 10.22 years in comparison to the OSF group that was 35.51 ± 11.26 years (P < 0.00). The mean habit duration was significantly less in the OSF group when compared to OSCCwOSFgroup for mishri (P = 0.002). Age-specific adjusted relative risk of OSCC in OSF patient increases from 0.33 (18-34 years) to 3.86 (≥65 years). CONCLUSION: It could be concluded that a 13.7% prevalence rate of OSCCwOSF in OSF patients should alert the clinician. Clinicians should, therefore, anticipate OSSC in OSF patients. This awareness could lead to the early diagnosis and management of such OSCC.

Comparison of the safety and efficacy of dexmedetomidine with midazolam for the management of paediatric dental patients: A systematic review.

BACKGROUND: Pain, fear, and anxiety have long been associated with pediatric dentistry. A child's cooperation with a dental.procedure.usually requires various behavioral management strategies conveyed by the entire dental team. The use of sedatives in dental clinics for providing analgesia and anxiolysis allows the patient to respond appropriately to verbal commands and light tactile stimulation., thus making dental treatment more patient friendly and effective. AIM: The aim of this study was to compare the safety and efficacy of dexmedetomidine versus midazolam for the management of pediatric patients in the dental clinic. MATERIALS AND METHODS: This systematic review was prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Six articles were selected for this systematic review. Of them, only in four articles, homogeneous data were available which were subjected to meta-analysis. RESULTS: When compared with midazolam, premedication with dexmedetomidine resulted in much lower incidence of emergence delirium (odds ratio = 0.07, 95% confidence interval: 0.01-0.54, P = 0.01). No significant difference was observed with respect to satisfactory behavior of the child, successful parental separation, and satisfactory mask acceptance following sedation. CONCLUSION: Both dexmedetomidine and midazolam are equally effective for the management of pediatric patients in the dental clinic. In addition, dexmedetomidine premedication is associated with lower incidence of emergence delirium and has a better margin of safety.

Phosphorylation of slit diaphragm proteins NEPHRIN and NEPH1 upon binding of HGF promotes podocyte repair.

Phosphorylation (activation) and dephosphorylation (deactivation) of the slit diaphragm proteins NEPHRIN and NEPH1 are critical for maintaining the kidney epithelial podocyte actin cytoskeleton and, therefore, proper glomerular filtration. However, the mechanisms underlying these events remain largely unknown. Here we show that NEPHRIN and NEPH1 are novel receptor proteins for hepatocyte growth factor (HGF) and can be phosphorylated independently of the mesenchymal epithelial transition receptor in a ligand-dependent fashion through engagement of their extracellular domains by HGF. Furthermore, we demonstrate SH2 domain-containing protein tyrosine phosphatase-2-dependent dephosphorylation of these proteins. To establish HGF as a ligand, purified baculovirus-expressed NEPHRIN and NEPH1 recombinant proteins were used in surface plasma resonance binding experiments. We report high-affinity interactions of NEPHRIN and NEPH1 with HGF, although NEPHRIN binding was 20-fold higher than that of NEPH1. In addition, using molecular modeling we constructed peptides that were used to map specific HGF-binding regions in the extracellular domains of NEPHRIN and NEPH1. Finally, using an in vitro model of cultured podocytes and an ex vivo model of Drosophila nephrocytes, as well as chemically induced injury models, we demonstrated that HGF-induced phosphorylation of NEPHRIN and NEPH1 is centrally involved in podocyte repair. Taken together, this is the first study demonstrating a receptor-based function for NEPHRIN and NEPH1. This has important biological and clinical implications for the repair of injured podocytes and the maintenance of podocyte integrity.

Comparative Evaluation of Indirect Pulp Therapy in Young Permanent Teeth using Biodentine and Theracal: A Randomized Clinical Trial.

OBJECTIVE: In a tooth with deep dentinal caries; judicious removal of infected dentin and isolating affected dentin from oral fluids with suitable biocompatible material is called indirect pulp therapy (IPT). This randomized clinical trial was done to evaluate and compare the efficacy of Biodentine, Theracal LC and. Dycal as an indirect pulp capping agent in young permanent teeth. STUDY DESIGN: IPT was performed in 60 young permanent molars with caries approaching pulp in 55 healthy children using Biodentine, Theracal and Dycal. A 2-3mm layer of GIC was placed over the intervening material followed by restoration of cavity with composite. Clinical and radiographic examinations were conducted at 3 weeks, 3 months, 6 months,12 months, 18 months and 24 months. The data was compared using chi-square test at a significance level of 0.05. RESULTS: By end of 24 months ,54 teeth presented for follow up with overall success rate of 100% in Theracal, 94.44% in Biodentine, and 77.78% in Dycal. Overall success of Theracal was statistically significant in comparison to Biodentine and Dycal at 24 months follow up (p= 0.03) Conclusions: Radiographic and clinical outcomes of Theracal and Biodentine suggest their use as an alternative material for IPT in young permanent molars with higher success.

Loss of Motor Protein MYO1C Causes Rhodopsin Mislocalization and Results in Impaired Visual Function.

Unconventional myosins, linked to deafness, are also proposed to play a role in retinal cell physiology. However, their direct role in photoreceptor function remains unclear. We demonstrate that systemic loss of the unconventional myosin MYO1C in mice, specifically causes rhodopsin mislocalization, leading to impaired visual function. Electroretinogram analysis of Myo1c knockout (Myo1c-KO) mice showed a progressive loss of photoreceptor function. Immunohistochemistry and binding assays demonstrated MYO1C localization to photoreceptor inner and outer segments (OS) and identified a direct interaction of rhodopsin with MYO1C. In Myo1c-KO retinas, rhodopsin mislocalized to rod inner segments (IS) and cell bodies, while cone opsins in OS showed punctate staining. In aged mice, the histological and ultrastructural examination of the phenotype of Myo1c-KO retinas showed progressively shorter photoreceptor OS. These results demonstrate that MYO1C is important for rhodopsin localization to the photoreceptor OS, and for normal visual function.

Targeting myosin 1c inhibits murine hepatic fibrogenesis.

Myosin 1c (Myo1c) is an unconventional myosin that modulates signaling pathways involved in tissue injury and repair. In this study, we observed that Myo1c expression is significantly upregulated in human chronic liver disease such as nonalcoholic steatohepatitis (NASH) and in animal models of liver fibrosis. High throughput data from the GEO-database identified similar Myo1c upregulation in mice and human liver fibrosis. Notably, transforming growth factor-ß1 (TGF-ß1) stimulation to hepatic stellate cells (HSCs), the liver pericyte and key cell type responsible for the deposition of extracellular matrix, upregulates Myo1c expression, whereas genetic depletion or pharmacological inhibition of Myo1c blunted TGF-ß-induced fibrogenic responses, resulting in repression of α-smooth muscle actin (α-SMA) and collagen type I α 1 chain (Col1α1) mRNA. Myo1c deletion also decreased fibrogenic processes such as cell proliferation, wound healing response, and contractility when compared with vehicle-treated HSCs. Importantly, phosphorylation of mothers against decapentaplegic homolog 2 (SMAD2) and mothers against decapentaplegic homolog 3 (SMAD3) were significantly blunted upon Myo1c inhibition in GRX cells as well as Myo1c knockout (Myo1c-KO) mouse embryonic fibroblasts (MEFs) upon TGF-ß stimulation. Using the genetic Myo1c-KO mice, we confirmed that Myo1c is critical for fibrogenesis, as Myo1c-KO mice were resistant to carbon tetrachloride (CCl4)-induced liver fibrosis. Histological and immunostaining analysis of liver sections showed that deposition of collagen fibers and α-SMA expression were significantly reduced in Myo1c-KO mice upon liver injury. Collectively, these results demonstrate that Myo1c mediates hepatic fibrogenesis by modulating TGF-ß signaling and suggest that inhibiting this process may have clinical application in treating liver fibrosis.NEW & NOTEWORTHY The incidences of liver fibrosis are growing at a rapid pace and have become one of the leading causes of end-stage liver disease. Although TGF-ß1 is known to play a prominent role in transforming cells to produce excessive extracellular matrix that lead to hepatic fibrosis, the therapies targeting TGF-ß1 have achieved very limited clinical impact. This study highlights motor protein myosin-1c-mediated mechanisms that serve as novel regulators of TGF-ß1 signaling and fibrosis.

Comparative Evaluation of Changes in Physiological and Psychomotor Effects in Pediatric Patients during Extraction under Different Concentrations of Nitrous Oxide-Oxygen Inhalation Sedation.

INTRODUCTION: Nonpharmacological behavioral management techniques are routinely used to create an environment that facilitates and builds a rapport between the child and the dentist to carry out procedures with minimal disruption. However, the discomfort associated with oral injections produces varying degrees of stress in all patients. Nitrous oxide (N2O)-oxygen (O2) inhalation sedation is one of the most widely used modalities for the management of fear and anxiety in children. OBJECTIVE: The objective was to evaluate changes in physiological and psychomotor effects in pediatric patients during extraction under different concentrations of N2O-O2 inhalation sedation. MATERIALS AND METHODS: A total of 300 healthy patients in the age range of 6-12 years (mean 8.9 years), who needed extraction of primary tooth, were included in the study. Pulse rate, SpO2, blood pressure (BP), and temperature were recorded at baseline, 30% N2O concentration, 50% N2O concentration, and again postoperatively. In addition, anxiety levels and neuromuscular coordination were recorded at the respective intervals. RESULTS: The results revealed a mean decrease in pulse rate and BP from baseline and an increase in temperature and O2 saturation during the sedation procedure. The findings were statistically significant. Significant impairment of coordination and psychomotor ability was seen at each step. Anxiety had significantly reduced after the onset of sedation due to the anxiolytic effect of N2O. CONCLUSION: N2O-O2 inhalation sedation under different concentrations reduces the anxiety of the patient and produces adequate sedation with vital signs within normal limits along with temporary impairment of psychomotor ability and coordination.

Repurposing of a Thromboxane Receptor Inhibitor Based on a Novel Role in Metastasis Identified by Phenome-Wide Association Study.

Although new drug discoveries are revolutionizing cancer treatments, repurposing existing drugs would accelerate the timeline and lower the cost for bringing treatments to cancer patients. Our goal was to repurpose CPI211, a potent and selective antagonist of the thromboxane A2-prostanoid receptor (TPr), a G-protein-coupled receptor that regulates coagulation, blood pressure, and cardiovascular homeostasis. To identify potential new clinical indications for CPI211, we performed a phenome-wide association study (PheWAS) of the gene encoding TPr, TBXA2R, using robust deidentified health records and matched genomic data from more than 29,000 patients. Specifically, PheWAS was used to identify clinical manifestations correlating with a TBXA2R single-nucleotide polymorphism (rs200445019), which generates a T399A substitution within TPr that enhances TPr signaling. Previous studies have correlated 200445019 with chronic venous hypertension, which was recapitulated by this PheWAS analysis. Unexpectedly, PheWAS uncovered an rs200445019 correlation with cancer metastasis across several cancer types. When tested in several mouse models of metastasis, TPr inhibition using CPI211 potently blocked spontaneous metastasis from primary tumors, without affecting tumor cell proliferation, motility, or tumor growth. Further, metastasis following intravenous tumor cell delivery was blocked in mice treated with CPI211. Interestingly, TPr signaling in vascular endothelial cells induced VE-cadherin internalization, diminished endothelial barrier function, and enhanced transendothelial migration by tumor cells, phenotypes that were decreased by CPI211. These studies provide evidence that TPr signaling promotes cancer metastasis, supporting the study of TPr inhibitors as antimetastatic agents and highlighting the use of PheWAS as an approach to accelerate drug repurposing.

Outcomes of luxation injuries to primary teeth-a systematic review.

OBJECTIVE: Luxation injuries are one of the most prevalent type traumatic dental injuries in primary dentition. The impact of these injuries may not only be limited to the primary teeth but may also have adverse effects on the developing succedaneous tooth bud resulting in various unfavorable consequences. This systematic review aims at compiling the evidence of available literature regarding luxation injuries to primary teeth, etiology, treatment modalities, outcomes and sequelae on permanent teeth. METHODOLOGY: Search of PubMed, Google Scholar, Cochrane Database of Systematic Reviews, SCOPUS and LILACS virtual health library was conducted for the literature published from January 1, 2007 to December 31, 2017. Two authors separately reviewed the literature and extracted the data from the included studies. RESULTS: After screening 224 articles, 13 articles fulfilled the inclusion criteria. Most common etiological factor for injury (up to 44.8%) is fall while walking or running. The unfavorable outcomes which are mostly associated with luxation injuries are pulp canal obliteration ranging from 8.6% to 43.3% and pulp necrosis 8.6% -78.9%. Sequelae on succedaneous teeth vary with a high incidence of white or yellow brown discoloration of enamel (78%) and enamel hypoplasia (7.8%-28.3%). CONCLUSION: Fall is the most common cause and regular monitoring is recommended for most of the luxated teeth. Pulp canal obliteration, pulp necrosis and tooth loss due to trauma are prevalent complications observed following luxation. White or yellow brown discoloration of enamel and enamel hypoplasia are the most common undesirable sequelae to permanent teeth.

Therapeutic inhibition of Mcl-1 blocks cell survival in estrogen receptor-positive breast cancers.

Cancers often overexpress anti-apoptotic Bcl-2 proteins for cell death evasion, a recognized hallmark of cancer progression. While estrogen receptor (ER)-α+ breast cancers express high levels of three anti-apoptotic Bcl-2 family members (Bcl-2, Bcl-xL, and Mcl-1), pharmacological inhibition of Bcl-2 and/or Bcl-xL fails to induce cell death in ERα+ breast cancer cell lines, due to rapid and robust Mcl-1 upregulation. The mechanisms of acute Mcl-1 upregulation in response to Bcl-2/Bcl-xL inhibition remain undefined in in ERα+ breast cancers. We report here that blockade of Bcl-2 or Bcl-xL, alone or together, rapidly induced mTOR signaling in ERα+ breast cancer cells, rapidly increasing cap-dependent Mcl-1 translation. Cells treated with a pharmacological inhibitor of cap-dependent translation, or with the mTORC1 inhibitor RAD001/everolimus, displayed reduced protein levels of Mcl-1 under basal conditions, and failed to upregulate Mcl-1 protein expression following treatment with ABT-263, a pharmacological inhibitor of Bcl-2 and Bcl-xL. Although treatment with ABT-263 alone did not sustain apoptosis in tumor cells in culture or in vivo, ABT-263 plus RAD001 increased apoptosis to a greater extent than either agent used alone. Similarly, combined use of the selective Mcl-1 inhibitor VU661013 with ABT-263 resulted in tumor cell apoptosis and diminished tumor growth in vivo. These findings suggest that rapid Mcl-1 translation drives ABT-263 resistance, but can be combated directly using emerging Mcl-1 inhibitors, or indirectly through existing and approved mTOR inhibitors.

Mitochondrial biogenesis induced by the ß2-adrenergic receptor agonist formoterol accelerates podocyte recovery from glomerular injury.

Podocytes have limited ability to recover from injury. Here, we demonstrate that increased mitochondrial biogenesis, to meet the metabolic and energy demand of a cell, accelerates podocyte recovery from injury. Analysis of events induced during podocyte injury and recovery showed marked upregulation of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a transcriptional co-activator of mitochondrial biogenesis, and key components of the mitochondrial electron transport chain. To evaluate our hypothesis that increasing mitochondrial biogenesis enhanced podocyte recovery from injury, we treated injured podocytes with formoterol, a potent, specific, and long-acting ß2-adrenergic receptor agonist that induces mitochondrial biogenesis in vitro and in vivo. Formoterol increased mitochondrial biogenesis and restored mitochondrial morphology and the injury-induced changes to the organization of the actin cytoskeleton in podocytes. Importantly, ß2-adrenergic receptors were found to be present on podocyte membranes. Their knockdown attenuated formoterol-induced mitochondrial biogenesis. To determine the potential clinical relevance of these findings, mouse models of acute nephrotoxic serum nephritis and chronic (Adriamycin [doxorubicin]) glomerulopathy were used. Mice were treated with formoterol post-injury when glomerular dysfunction was established. Strikingly, formoterol accelerated the recovery of glomerular function by reducing proteinuria and ameliorating kidney pathology. Furthermore, formoterol treatment reduced cellular apoptosis and increased the expression of the mitochondrial biogenesis marker PGC-1α and multiple electron transport chain proteins. Thus, our results support ß2-adrenergic receptors as novel therapeutic targets and formoterol as a therapeutic compound for treating podocytopathies.

The motor protein Myo1c regulates transforming growth factor-ß-signaling and fibrosis in podocytes.

Transforming growth factor-ß (TGF-ß) is known to play a critical role in the pathogenesis of many progressive podocyte diseases. However, the molecular mechanisms regulating TGF-ß signaling in podocytes remain unclear. Using a podocyte-specific myosin (Myo)1c knockout, we demonstrate whether Myo1c is critical for TGF-ß-signaling in podocyte disease pathogenesis. Specifically, podocyte-specific Myo1c knockout mice were resistant to fibrotic injury induced by Adriamycin or nephrotoxic serum. Further, loss of Myo1c also protected from injury in the TGF-ß-dependent unilateral ureteral obstruction mouse model of renal interstitial fibrosis. Mechanistic analyses showed that loss of Myo1c significantly blunted TGF-ß signaling through downregulation of canonical and non-canonical TGF-ß pathways. Interestingly, nuclear rather than the cytoplasmic Myo1c was found to play a central role in controlling TGF-ß signaling through transcriptional regulation. Differential expression analysis of nuclear Myo1c-associated gene promoters showed that nuclear Myo1c targeted the TGF-ß responsive gene growth differentiation factor (GDF)-15 and directly bound to the GDF-15 promoter. Importantly, GDF15 was found to be involved in podocyte pathogenesis, where GDF15 was upregulated in glomeruli of patients with focal segmental glomerulosclerosis. Thus, Myo1c-mediated regulation of TGF-ß-responsive genes is central to the pathogenesis of podocyte injury. Hence, inhibiting this process may have clinical application in treating podocytopathies.

Disruption of the exocyst induces podocyte loss and dysfunction.

Although the slit diaphragm proteins in podocytes are uniquely organized to maintain glomerular filtration assembly and function, little is known about the underlying mechanisms that participate in trafficking these proteins to the correct location for development and homeostasis. Identifying these mechanisms will likely provide novel targets for therapeutic intervention to preserve podocyte function following glomerular injury. Analysis of structural variation in cases of human nephrotic syndrome identified rare heterozygous deletions of EXOC4 in two patients. This suggested that disruption of the highly-conserved eight-protein exocyst trafficking complex could have a role in podocyte dysfunction. Indeed, mRNA profiling of injured podocytes identified significant exocyst down-regulation. To test the hypothesis that the exocyst is centrally involved in podocyte development/function, we generated homozygous podocyte-specific Exoc5 (a central exocyst component that interacts with Exoc4) knockout mice that showed massive proteinuria and died within 4 weeks of birth. Histological and ultrastructural analysis of these mice showed severe glomerular defects with increased fibrosis, proteinaceous casts, effaced podocytes, and loss of the slit diaphragm. Immunofluorescence analysis revealed that Neph1 and Nephrin, major slit diaphragm constituents, were mislocalized and/or lost. mRNA profiling of Exoc5 knockdown podocytes showed that vesicular trafficking was the most affected cellular event. Mapping of signaling pathways and Western blot analysis revealed significant up-regulation of the mitogen-activated protein kinase and transforming growth factor-ß pathways in Exoc5 knockdown podocytes and in the glomeruli of podocyte-specific Exoc5 KO mice. Based on these data, we propose that exocyst-based mechanisms regulate Neph1 and Nephrin signaling and trafficking, and thus podocyte development and function.