Peter Pytel

University of Chicago, Chicago, Illinois, United States

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Publications (75)319.96 Total impact

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    ABSTRACT: Introduction: Adult polyglucosan body disease (APBD) is associated with formation of polyglucosan bodies in peripheral nerve branches. Some muscle biopsies show these inclusions in intramuscular nerve branches. It has not been established whether the presence of multiple polyglucosan bodies in intramuscular peripheral nerve branches could or should suggest testing for APBD. Methods: 15 muscle biopsies from adults between ages 36 and 84 years, all showing polyglucosan bodies in intramuscular peripheral nerve twigs, were tested by sequencing of the GBE1 gene. Results: In 4 patients testing identified heterozygous missense mutations not previously described. No homozygous or compound heterozygous mutations were identified. Conclusions: The presence of polyglucosan bodies in intramuscular nerve twigs by itself, even if they are multiple, is not an indication of APBD. Further testing may only be indicated in patients with clinical disease manifestations. This article is protected by copyright. All rights reserved.
    No preview · Article · Dec 2015 · Muscle & Nerve
  • A. Daher · R. Lukas · P. Pytel · M. K. Nicholas

    No preview · Article · Nov 2015 · Neuro-Oncology
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    Preview · Article · Nov 2015
  • Bonnie Choy · Peter Pytel
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    ABSTRACT: Myoepithelial neoplasms were originally described in the salivary glands but their spectrum has been expanding with reports in other locations, including soft tissue. Intracranial cases are exceptionally rare outside the sellar region where they are assumed to be arising from Rathke pouch rests. Two cases of pediatric intracranial myoepithelial neoplasm in the interhemispheric fissure and the right cerebral hemisphere are reported here. Imaging studies suggest that the second case was associated with cerebrospinal fluid dissemination. Both cases showed typical variation in morphology and immunophenotype between more epithelioid and more mesenchymal features. The differential diagnosis at this particular anatomic location includes meningioma, which can show some overlap in immunophenotype since both tumors express EMA as well as GLUT1. One case was positive for EWSR1 rearrangement by fluorescence in situ hybridization. One patient is disease free at last follow-up while the other succumbed to the disease within days illustrating the clinical spectrum of these tumors.
    No preview · Article · Oct 2015 · International Journal of Surgical Pathology
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    ABSTRACT: We previously showed that Eps15 homology domain-containing 1 (EHD1) interacts with ferlin proteins to regulate endocytic recycling. Myoblasts from Ehd1-null mice were found to have defective recycling, myoblast fusion, and consequently smaller muscles. When expressed in C2C12 cells, an ATPase dead-EHD1 was found to interfere with BIN1/amphiphysin 2. We now extended those findings by examining Ehd1-heterozygous mice since these mice survive to maturity in normal Mendelian numbers and provide a ready source of mature muscle. We found that heterozygosity of EHD1 was sufficient to produce ectopic and excessive T-tubules, including large intracellular aggregates that contained BIN1. The disorganized T-tubule structures in Ehd1-heterozygous muscle were accompanied by marked elevation of the T-tubule-associated protein DHPR and reduction of the triad linker protein junctophilin 2, reflecting defective triads. Consistent with this, Ehd1-heterozygous muscle had reduced force production. Introduction of ATPase dead-EHD1 into mature muscle fibers was sufficient to induce ectopic T-tubule formation, seen as large BIN1 positive structures throughout the muscle. Ehd1-heterozygous mice were found to have strikingly elevated serum creatine kinase and smaller myofibers, but did not display findings of muscular dystrophy. These data indicate that EHD1 regulates the maintenance of T-tubules through its interaction with BIN1 and links T-tubules defects with elevated creatine kinase and myopathy.
    Full-text · Article · Sep 2015 · PLoS ONE
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    ABSTRACT: Myostatin is a secreted signaling molecule that normally acts to limit muscle growth. As a result, there is extensive effort directed at developing drugs capable of targeting myostatin to treat patients with muscle loss. One potential concern with this therapeutic approach in patients with muscle degenerative diseases like muscular dystrophy is that inducing hypertrophy may increase stress on dystrophic fibers, thereby accelerating disease progression. To investigate this possibility, we examined the effect of blocking the myostatin pathway in dysferlin-deficient (Dysf(-/-)) mice, in which membrane repair is compromised, either by transgenic expression of follistatin in skeletal muscle or by systemic administration of the soluble form of the activin type IIB receptor (ACVR2B/Fc). Here, we show that myostatin inhibition by follistatin transgene expression in Dysf(-/-) mice results in early improvement in histopathology but ultimately exacerbates muscle degeneration; this effect was not observed in dystrophin-deficient (mdx) mice, suggesting that accelerated degeneration induced by follistatin transgene expression is specific to mice lacking dysferlin. Dysf(-/-) mice injected with ACVR2B/Fc showed significant increases in muscle mass and amelioration of fibrotic changes normally seen in 8 month old Dysf(-/-) mice. Despite these potentially beneficial effects, ACVR2B/Fc treatment caused increases in serum CK levels in some Dysf(-/-) mice, indicating possible muscle damage induced by hypertrophy. These findings suggest that depending on the disease context, inducing muscle hypertrophy by myostatin blockade may have detrimental effects, which need to be weighed against the potential gains in muscle growth and decreased fibrosis. © The Author 2015. Published by Oxford University Press.
    Preview · Article · Jul 2015 · Human Molecular Genetics
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    ABSTRACT: Glioma stem cells (GSCs) constitute a slow-dividing, small population within a heterogeneous glioblastoma. They are able to self-renew, recapitulate a whole tumor, and differentiate into other specific glioblastoma multiforme (GBM) subpopulations. Therefore, they have been held responsible for malignant relapse after primary standard therapy and the poor prognosis of recurrent GBM. The failure of current therapies to eliminate specific GSC subpopulations has been considered a major factor contributing to the inevitable recurrence in GBM patients after treatment. Here, we discuss the molecular mechanisms of chemoresistance of GSCs and the reasons why complete eradication of GSCs is so difficult to achieve. We will also describe the targeted therapies currently available for GSCs and possible mechanisms to overcome such chemoresistance and avoid therapeutic relapse.
    No preview · Article · May 2015 · Expert Review of Neurotherapeutics
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    ABSTRACT: Dendritic cells (DCs) are professional APCs that are traditionally divided into two distinct subsets, myeloid DC (mDCs) and plasmacytoid DC (pDCs). pDCs are known for their ability to secrete large amounts of IFN-α. Apart from IFN-α production, pDCs can also process Ag and induce T cell immunity or tolerance. In several solid tumors, pDCs have been shown to play a critical role in promoting tumor immunosuppression. We investigated the role of pDCs in the process of glioma progression in the syngeneic murine model of glioma. We show that glioma-infiltrating pDCs are the major APC in glioma and are deficient in IFN-α secretion (p < 0.05). pDC depletion leads to increased survival of the mice bearing intracranial tumor by decreasing the number of regulatory T cells (Tregs) and by decreasing the suppressive capabilities of Tregs. We subsequently compared the ability of mDCs and pDCs to generate effective antiglioma immunity in a GL261-OVA mouse model of glioma. Our data suggest that mature pDCs and mDCs isolated from naive mice can be effectively activated and loaded with SIINFEKL Ag in vitro. Upon intradermal injection in the hindleg, a fraction of both types of DCs migrate to the brain and lymph nodes. Compared to mice vaccinated with pDC or control mice, mice vaccinated with mDCs generate a robust Th1 type immune response, characterized by high frequency of CD4(+)T-bet(+) T cells and CD8(+)SIINFEKEL(+) T cells. This robust antitumor T cell response results in tumor eradication and long-term survival in 60% of the animals (p < 0.001). Copyright © 2015 by The American Association of Immunologists, Inc.
    Full-text · Article · May 2015 · The Journal of Immunology
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    Full-text · Article · Apr 2015

  • No preview · Article · Mar 2015 · Brain Pathology
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    ABSTRACT: Brain metastases occur in about 10-30% of breast cancer patients, which culminates in a poor prognosis. It is therefore critical to understand the molecular mechanisms underlying brain metastatic processes to identify relevant targets. We hypothesized that breast cancer cells must express brain-associated markers that would enable their invasion and survival in the brain microenvironment. We assessed a panel of brain-predominant markers and found an elevation of several neuronal markers (βIII tubulin, Nestin and AchE) in brain metastatic breast cancer cells. Among these neuronal predominant markers, in silico analysis revealed overexpression of βIII tubulin (TUBB3) in breast cancer brain metastases (BCBM) and its expression was significantly associated with distant metastases. TUBB3 knockdown studies were conducted in breast cancer models (MDA-Br, GLIM2 and MDA-MB-468) which revealed significant reduction in their invasive capabilities. MDA-Br cells with suppressed TUBB3 also demonstrated loss of key signaling molecules such as beta 3 integrin, pFAK, and pSrc in vitro. Furthermore, TUBB3 knockdown in a brain metastatic breast cancer cell line compromised its metastatic ability in vivo, and significantly improved survival in a brain metastasis model. These results implicate a critical role of TUBB3 in conferring brain metastatic potential to breast cancer cells. Copyright © 2015, American Association for Cancer Research.
    No preview · Article · Feb 2015 · Molecular Cancer Therapeutics

  • No preview · Conference Paper · Feb 2015
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    ABSTRACT: The enchondromatoses, Ollier's disease and Maffucci syndrome, are non-heritable developmental disorders characterized by multiple enchondromas (Olllier's) in association with hemangiomas (Maffucci). Glial neoplasms are reported in both disorders but a pathogenic mechanism underlying this association has not been identified. We report a case of anaplastic astrocytoma in a 23 year old man with Maffucci syndrome whose tumor carried a substitution mutation of arginine for cysteine at position 132 (R132C) of the isocitrate dehydrogenase 1 (IDH1) protein. This mutation, commonly found in Maffucci-associated enchondromas and hemangiomas, was not detected on routine immunohistochemical (IHC) analysis of the astrocytoma using the R132H mutation-specific antibody, commonly applied in clinical laboratories. The R132C mutation was detected by polymerase chain reaction (PCR) and subsequently confirmed using a SNaPshot assay. Because somatic mosaic IDH mutations are associated with enchondromas and hemangiomas in Maffucci syndrome, we looked for the R132C mutation in a hemangioma, peripheral blood mononuclear cells (PBMNC) and histologically normal brain surrounding the tumor from this patient. The mutation was present in the hemangioma, absent in PBMNC, and present in 2% of alleles in ‘normal’ brain. The low level in surrounding brain tissue is consistent with tumor cell infiltration, not mosaicism, as a S173T p53 mutation in the tumor showed similar results. Using IHC, we further demonstrated that the mutant IDH1 protein in this glioma functions as an oncometabolite. Two repressive histone trimethylation marks were strongly positive in the tumor, supporting a role for 2-hydroxyglutarate in the inhibition of histone demethylation. Together, these data demonstrate that an IDH1 mutation common in enchodromatoses underlies the association of glial tumors reported in both Ollier's disease and Maffucci syndrome.
    No preview · Article · Nov 2014 · Neuro-Oncology
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    ABSTRACT: NF-κB is a major regulator of age-dependent gene expression and the p50/NF-κB1 subunit is an integral modulator of NF-κB signaling. Here, we examined Nfkb1-/- mice to investigate the relationship between this subunit and aging. Although Nfkb1-/- mice appear similar to littermates at six months of age, by 12 months they have a higher incidence of several observable age-related phenotypes. In addition, aged Nfkb1-/- animals have increased kyphosis, decreased cortical bone, increased brain GFAP staining and a decrease in overall lifespan compared to Nfkb1+/+. In vitro, serially passaged primary Nfkb1-/- MEFs have more senescent cells than comparable Nfkb1+/+ MEFs. Also, Nfkb1-/- MEFs have greater amounts of phospho-H2AX foci and lower levels of spontaneous apoptosis than Nfkb1+/+, findings that are mirrored in the brains of Nfkb1-/- animals compared to Nfkb1+/+. Finally, in wildtype animals a substantial decrease in p50 DNA binding is seen in aged tissue compared to young. Together, these data show that loss of Nfkb1 leads to early animal aging that is associated with reduced apoptosis and increased cellular senescence. Moreover, loss of p50 DNA binding is a prominent feature of aged mice relative to young. These findings support the strong link between the NF-κB pathway and mammalian aging.
    Full-text · Article · Nov 2014 · Aging
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    ABSTRACT: The slow-channel congenital myasthenic syndrome (SCS) is an inherited neurodegenerative disease that caused mutations in the acetylcholine receptor (AChR) affecting neuromuscular transmission. Leaky AChRs lead to Ca(2+) overload and degeneration of the neuromuscular junction (NMJ) attributed to activation of cysteine proteases and apoptotic changes of synaptic nuclei. Here we use transgenic mouse models expressing two different mutations found in SCS to demonstrate that inhibition of prolonged opening of mutant AChRs using fluoxetine not only improves motor performance and neuromuscular transmission but also prevents Ca(2+) overload, the activation of cysteine proteases, calpain, caspase-3 and 9 at endplates, and as a consequence, reduces subsynaptic DNA damage at endplates, suggesting a long term benefit to therapy. These studies suggest that prolonged treatment of SCS patients with open ion channel blockers that preferentially block mutant AChRs is neuroprotective. Copyright © 2014 Elsevier Inc. All rights reserved.
    No preview · Article · Oct 2014 · Experimental Neurology
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    ABSTRACT: Background: Cardiomyopathy is highly heritable but genetically diverse. At present, genetic testing for cardiomyopathy uses targeted sequencing to simultaneously assess the coding regions of >50 genes. New genes are routinely added to panels to improve the diagnostic yield. With the anticipated $1000 genome, it is expected that genetic testing will shift toward comprehensive genome sequencing accompanied by targeted gene analysis. Therefore, we assessed the reliability of whole genome sequencing and targeted analysis to identify cardiomyopathy variants in 11 subjects with cardiomyopathy. Methods and results: Whole genome sequencing with an average of 37× coverage was combined with targeted analysis focused on 204 genes linked to cardiomyopathy. Genetic variants were scored using multiple prediction algorithms combined with frequency data from public databases. This pipeline yielded 1 to 14 potentially pathogenic variants per individual. Variants were further analyzed using clinical criteria and segregation analysis, where available. Three of 3 previously identified primary mutations were detected by this analysis. In 6 subjects for whom the primary mutation was previously unknown, we identified mutations that segregated with disease, had clinical correlates, and had additional pathological correlation to provide evidence for causality. For 2 subjects with previously known primary mutations, we identified additional variants that may act as modifiers of disease severity. In total, we identified the likely pathological mutation in 9 of 11 (82%) subjects. Conclusions: These pilot data demonstrate that ≈30 to 40× coverage whole genome sequencing combined with targeted analysis is feasible and sensitive to identify rare variants in cardiomyopathy-associated genes.
    Preview · Article · Sep 2014 · Circulation Cardiovascular Genetics

  • No preview · Article · Jun 2014 · International Journal of Surgical Pathology
  • Peter Pytel
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    ABSTRACT: The diagnosis of an inflammatory myopathy is often established based on basic histologic studies. Additional immunohistochemical studies are sometimes required to support the diagnosis and the classification of inflammatory myopathies. Staining for major histocompatibility complex 1 (MHC1) often shows increased sarcolemmal labeling in inflammatory myopathies. Endomysial capillary staining C5b-9 (membrane attack complex) is a feature that is reported as frequently associated with dermatomyositis. Immunohistochemical staining for C4d is widely used for various applications including the assessment of antibody-mediated rejection after solid organ transplantation. In the context of dermatomyositis, C4d staining has been described in skin biopsies but not in muscle biopsies. A total of 32 muscle biopsy specimens were examined. The hematoxylin and eosin-stained slides were reviewed, and immunohistochemical studies for MHC1, C5b-9, and C4d were conducted. The staining observed for C5b-9 and C4d was compared. Overall, the staining pattern for C4d mirrored the one observed for C5b-9 in the examined muscle biopsy specimens. There was high and statistically significant (P<0.0001) correlation between the staining seen with these 2 antibodies. Both antibodies labeled the cytoplasm of degenerating necrotic myofibers. In addition, both antibodies showed distinct endomysial capillary labeling in a subset of dermatomyositis. Areas with perifascicular atrophy often exhibited the most prominent vascular labeling for C4d and C5b-9. In conclusion, C4d and C5b-9 show similar expression patterns in muscle biopsies of patients with inflammatory myopathies and both highlight the presence of vascular labeling associated with dermatomyositis. C4d antibodies are widely used and may offer an alternative for C5b-9 staining.
    No preview · Article · Jun 2014 · Applied immunohistochemistry & molecular morphology: AIMM / official publication of the Society for Applied Immunohistochemistry
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    ABSTRACT: Microarray-based molecular signatures have not been widely integrated into neuroblastoma diagnostic classification systems due to the complexities of the assay and requirement for high-quality RNA. New digital technologies that accurately quantify gene expression using RNA isolated from formalin-fixed paraffin embedded (FFPE) tissues are now available. In this study, we describe the first use of a high-throughput digital system to assay the expression of genes in an “ultra-high risk” microarray classifier in FFPE high-risk neuroblastoma tumors. Customized probes corresponding to the 42 genes in a published multi-gene neuroblastoma signature were hybridized to RNA isolated from 107 FFPE high-risk neuroblastoma samples using the NanoString nCounterTM Analysis System. For classification of each patient, the Pearson's correlation coefficient was calculated between the standardized nCounterTM data and the molecular signature from the microarray data. We demonstrate that the nCounterTM 42-gene panel sub-stratified the high-risk cohort into two subsets with statistically significantly different overall survival (p=0.0027) and event-free survival (p=0.028). In contrast, none of the established prognostic risk markers (age, stage, tumor histology, MYCN status, and ploidy) were significantly associated with survival. We conclude that the nCounterTM System can reproducibly quantify expression levels of signature genes in FFPE tumor samples. Validation of this microarray signature in our high-risk patient cohort using a completely different technology emphasizes the prognostic relevance of this classifier. Prospective studies testing the prognostic value of molecular signatures in high-risk neuroblastoma patients using FFPE tumor samples and the nCounterTM System are warranted.
    No preview · Article · May 2014 · Molecular oncology
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    ABSTRACT: EHD proteins have been implicated in intracellular trafficking, especially endocytic recycling, where they mediate receptor and lipid recycling back to the plasma membrane. Additionally, EHDs help regulate cytoskeletal reorganization and induce tubule formation. It was previously shown that EHD proteins bind directly to the C2 domains in myoferlin, a protein that regulates myoblast fusion. Loss of myoferlin impairs normal myoblast fusion leading to smaller muscles in vivo but the intracellular pathways perturbed by loss of myoferlin function are not well known. We now characterized muscle development in EHD1-null mice. EHD1-null myoblasts display defective receptor recycling and mislocalization of key muscle proteins, including caveolin-3 and Fer1L5, a related ferlin protein homologous to myoferlin. Additionally, EHD1-null myoblast fusion is reduced. We found that loss of EHD1 leads to smaller muscles and myofibers in vivo. In wildtype skeletal muscle EHD1 localizes to the transverse tubule (T-tubule), and loss of EHD1 results in overgrowth of T-tubules with excess vesicle accumulation in skeletal muscle. We provide evidence that tubule formation in myoblasts relies on a functional EHD1 ATPase domain. Moreover, we extended our studies to show EHD1 regulates BIN1 induced tubule formation. These data, taken together and with the known interaction between EHD and ferlin proteins, suggests that the EHD proteins coordinate growth and development likely through mediating vesicle recycling and the ability to reorganize the cytoskeleton.
    No preview · Article · Jan 2014 · Developmental Biology