Jogi V. Pattisapu

Receptor Channel TRPC6 Is a Key Mediator of Notch-Driven Glioblastoma Growth and Invasiveness

Glioblastoma multiforme (GBM) is the most frequent and incurable type of brain tumor of adults. Hypoxia has been shown to direct GBM toward a more aggressive and malignant state. Here we show that hypoxia increases Notch1 activation, which in turn induces the expression of transient receptor potential 6 (TRPC6) in primary samples and cell lines derived from GBM. TRPC6 is required for the development of the aggressive phenotype because knockdown of TRPC6 expression inhibits glioma growth, invasion, and angiogenesis. Functionally, TRPC6 causes a sustained elevation of intracellular calcium that is coupled to the activation of the calcineurin-nuclear factor of activated T-cell (NFAT) pathway. Pharmacologic inhibition of the calcineurin-NFAT pathway substantially reduces the development of the malignant GBM phenotypes under hypoxia. Clinically, expression of TRPC6 was elevated in GBM specimens in comparison with normal tissues. Collectively, our studies indicate that TRPC6 is a key mediator of tumor growth of GBM in vitro and in vivo and that TRPC6 may be a promising therapeutic target in the treatment of human GBM.

Stress-induced Switch in Numb Isoforms Enhances Notch-dependent Expression of Subtype-specific Transient Receptor Potential Channel

The Notch signaling pathway plays an essential role in the regulation of cell specification by controlling differentiation, proliferation, and apoptosis. Numb is an intrinsic regulator of the Notch pathway and exists in four alternative splice variants that differ in the length of their phosphotyrosine-binding domain (PTB) and proline-rich region domains. The physiological relevance of the existence of the Numb splice variants and their exact regulation are still poorly understood. We previously reported that Numb switches from isoforms containing the insertion in PTB to isoforms lacking this insertion in neuronal cells subjected to trophic factor withdrawal (TFW). The functional relevance of the TFW-induced switch in Numb isoforms is not known. Here we provide evidence that the TFW-induced switch in Numb isoforms regulates Notch signaling strength and Notch target gene expression. PC12 cells stably overexpressing Numb isoforms lacking the PTB insertion exhibited higher basal Notch activity and Notch-dependent transcription of the transient receptor potential channel 6 (TRPC6) when compared with those overexpressing Numb isoforms with the PTB insertion. The differential regulation of TRPC6 expression is correlated with perturbed calcium signaling and increased neuronal vulnerability to TFW-induced death. Pharmacological inhibition of the Notch pathway or knockdown of TRPC6 function ameliorates the adverse effects caused by the TFW-induced switch in Numb isoforms. Taken together, our results indicate that Notch and Numb interaction may influence the sensitivity of neuronal cells to injurious stimuli by modulating calcium-dependent apoptotic signaling cascades.

Evidence for altered numb isoform levels in alzheimer's disease patients and a triple transgenic mouse model

The cell fate determinant Numb exists in four alternatively spliced variants that differ in the length of their PTB (phosphotyrosine-binding domain, either lacking or containing an 11 amino acid insertion) and PRR (proline-rich region, either lacking or containing a 48 amino acid insertion). We previously reported that Numb switches from isoforms containing the PTB insertion to isoforms lacking this insertion in neural cultures subjected to stress induced by trophic factor withdrawal. The switch in Numb isoforms enhances the generation of amyloid-β peptide (Aβ), the principle component of senile plaques in Alzheimers disease (AD). Here we examine the expression of the Numb isoforms in brains from AD patients and triple transgenic (3xTg) AD mice. We found that levels of the Numb isoforms lacking the PTB insertion are significantly elevated in the parietal cortex but not in the cerebellum of AD patients when compared to control subjects. Levels of Numb isoforms lacking the PTB insertion were also elevated in the cortex but not cerebellum of 12 month-old 3xTg AD mice with Aβ deposits compared to younger 3xTg-AD mice and to non-transgenic mice. Exposure of cultured neurons to Aβ resulted in an increase in the levels of Numb isoforms lacking the PTB domain, consistent with a role for Aβ in the aberrant expression of Numb in vulnerable brain regions of AD patients and mice. Collectively, the data show that altered expression of Numb isoforms in vulnerable neurons occurs during AD pathogenesis and suggest a role for Numb in the disease process.

Evidence for reduced lymphatic CSF absorption in the H-Tx rat hydrocephalus model

BackgroundThere is mounting evidence that spinal fluid absorption takes place not only at the arachnoid villi, but also at several extracranial sites, which might serve as a reserve mechanism for, or be primarily involved in the absorption of CSF in hydrocephalus.MethodsWe compared the nasal lymphatic pathway in congenital Hydrocephalus-Texas (H-Tx) rats in unaffected and affected hydrocephalic (HC) siblings with that of control Sprague Dawley (SD) rat pups. The animals were examined after immediate post mortem injection of Evans blue dye into the cisterna magna at 6 and 10 days of age. The specimens were evaluated for amount of dye penetration into the nasal passages.ResultsWe found more dye visualization in the olfactory regions of control SD (14/16 at P6, 14/16 at P10) and unaffected H-Tx (13/17 at P6, 13/16 at P10) compared with HC animals (0/14 at P6, 3/15 at P10). This difference was more pronounced at 10 days of age. The dye was not visualized in the cervical lymph nodes or venous channels in these acute experiments.ConclusionThe results of this study suggest that nasal lymphatic cerebrospinal fluid absorption is reduced in the H-Tx rat hydrocephalus model.

The altered expression of aquaporin 1 and 4 in choroid plexus of congenital hydrocephalus

Background Aquaporins are a group of bidirectional transmembrane water channels that are involved in maintaining brain water homeostasis. Aquaporin 1 is primarily expressed in the ventricular choroid plexus, and it is involved in cerebrospinal fluid production. Aquaporin 4 is localized to the astrocyte end feet, ependyma, and glia limitans. The present study documents the alteration of expression of aquaporins 1 and 4 in hydrocephalus, and the ability of Vinpocetine (a vinca alkaloid that activates the pKC pathway) to regulate AQP1 and 4 in a choroid plexus cell line.

Filament-associated TSGA10 protein is expressed in professional antigen presenting cells and interacts with vimentin

Testis-specific gene antigen 10 (TSGA10) encodes an 82-kDa protein expressed during development, and in testis and brain tissues. We report its expression in human monocyte-derived dendritic cells (DC) and macrophages in vitro and in murine spleen CD11c(+) cells ex vivo. An interaction between DC/macrophage-derived TSGA10 and vimentin, as well as a few other major cytoskeletal proteins (e.g., actin-γ1), was identified by pull-down and mass spectroscopy assays. The interaction between TSGA10 and vimentin was further confirmed by immunoprecipitation and immunolocalisation in transfected RAW267 and HEK293 cell lines. TSGA10 formed filamentous structures in transfected COS-1 cells and was observed in cellular projections. We propose that TSGA10 could influence the function of antigen presenting cells (APC) via its interaction with cytoskeletal proteins such as vimentin.

The Coronal Scalp Flap: Surgical Technique

Ramon L. Ruiz, DMD, MD*, Jogi V. Pattisapu, MD, Bernard J. Costello, DMD, MD, Brent Golden, DDS, MD Arnold Palmer Hospital for Children, 83 West Columbia Street, Orlando, FL 32806, USA University of Central Florida College of Medicine, Health Sciences Campus at Lake Nona, 6850 Lake Nona Boulevard, Orlando, FL 32827, USA Oral & Maxillofacial Surgery, University of Pittsburgh College of Dental Medicine, Pittsburgh, PA, USA Oral & Maxillofacial Surgery Residency, University of Pittsburgh College of Dental Medicine, Pittsburgh, PA, USA Pediatric Cleft & Craniofacial Surgery Fellowship Program, University of Pittsburgh College of Dental Medicine, Pittsburgh, PA, USA

Arachnoid cysts: a diffuse spinal fluid absorption abnormality?

Background Cerebrospinal fluid (CSF) homeostasis is quite complex, and does not always present in a diffuse form such as hydrocephalus. In some situations, a focal manifestation of this global circulation abnormality is identified, such as arachnoid cysts (most often in the temporal fossa). These patients with temporal arachnoid cysts develop shunt dependency, as spinal fluid circulation seems to be affected permanently.

Expression of aquaporins in a transgenic mouse model of Alzheimer's disease

Background Several studies reported altered expression of the water channels, aquaporins (AQPs), in brains of Alzheimer’s disease (AD) but the relevance of the observed changes with respect to the neuropathology of AD is poorly understood. Because aberrant processing of the amyloid precursor protein (APP) to amyloid beta-peptide (A-beta), the principle component of amyloid plaques, is central to the pathogenesis of AD, we sought to determine the temporal and spatial expression of AQPs in the cortex and hippocampus of the triple transgenic mouse model of Alzheimer’s disease (3xTg-AD) and to elucidate whether AQPs contribute directly to the aberrant processing of APP into A-beta.

CSF Fistulae as a Complication Due to Insufficient Correction of Altered CSF Dynamics

Hydrocephalus is a complex phenomenon and incomplete knowledge about CSF dynamics often complicates our understanding and management of symptoms in children with altered fluid mechanisms. Patients with low-pressure symptoms are sometimes misdiagnosed, and complications occur in children with CSF fistulae that interfere with proper management of the hydrocephalic condition.