An atypical presentation of diffuse midline pontine glioma in a middle age patient: Case report.

INTRODUCTION: Diffuse midline glioma is a newly WHO defined entity (grade IV) (Louis et al., 2016) which includes diffuse intrinsic pontine glioma (DIPG) reported in pediatric population and, occasionally, in young adults. Here, we present a detailed description of an atypical case of diffuse midline glioma in a 53 years old woman. CASE REPORT: A caucasian woman aged 53 from Ukraine, was referred to another neurological department complaining of 3 months history of progressive postural instability and gait impairment with frequent falling. Magnetic resonance demonstrated two brainstem lesions, hyperintense in FLAIR with "patchy" peripheral enhancement, leptomeningeal and cranial nerves enhancement. CSF was normal. Due to positive antinuclear antibodies test (ANA 1:360), intravenous steroid treatment was administered and reported to initially improve the patient condition. However, the following weeks the lady worsened. Imaging features were unchanged. Because quantiferon test resulted positive, MRI-Spectroscopy showed an inflammatory pattern and MRI perfusion study and brain FDG-PET, were normal, tubercolar granulomatous hypothesis was initially favored. Antitubercular therapy with isoniazid, pyrazinamide, ethambutol and rifampicin was started without any clinical improvement. Hence, the biopsy was proposed. The procedure revealed a diffuse midline pontine glioma. Considering the advanced stage of the disease, radiotherapy was not indicated. Patient died after eight months from the onset of neurological disturbances. CONCLUSION: Our case shows that diffuse midline glioma is a CNS tumor not limited to young population but occurring also in middle aged patients with an insidious pattern. We therefore recommend to perform biopsy at very early stages in patients with atypical brainstem lesions.

FYVE finger proteins as effectors of phosphatidylinositol 3-phosphate.

Phosphatidylinositol 3-phosphate (PtdIns(3)P), generated via the phosphorylation of phosphatidylinositol by phosphatidylinositol 3-kinase (PI 3-kinase), plays an essential role in intracellular membrane traffic. The underlying mechanism is still not understood in detail, but the recent identification of the FYVE finger as a protein domain that binds specifically to PtdIns(3)P provides a number of potential effectors for PtdIns(3)P. The FYVE finger (named after the first letter of the four proteins containing it; Fab1p, YOTB, Vac1p and EEA1) is a double-zinc binding domain that is conserved in more than 30 proteins from yeast to mammals. It is found in several proteins involved in intracellular traffic, and FYVE finger mutations that affect zinc binding are associated with the loss of function of several of these proteins. The interaction of FYVE fingers with PtdIns(3)P may serve three alternative functions: First, to recruit cytosolic FYVE finger proteins to PtdIns(3)P-containing membranes (in concert with accessory molecules); second, to enrich for membrane bound FYVE finger proteins into PtdIns(3)P containing microdomains within the membrane; and third, to modulate the activity of membrane bound FYVE finger proteins.

Microtubules are involved in bafilomycin A1-induced tubulation and Rab5-dependent vacuolation of early endosomes.

The small GTPase Rab5 is an important regulator of membrane fusion in the early endocytic pathway. Here we have studied at the light microscopy level the morphology of early endosomes in MDCK cells stably expressing a GTPase-deficient Rab5 mutant, Rab5 Q79L, N-terminally tagged with a myc-epitope. These cells contain large vacuoles, readily visible by phase-contrast microscopy. Confocal immunofluorescence microscopy showed the presence of the epitopetagged protein on large perinuclear vacuoles, as well as on smaller peripheral structures. A subset of the perinuclear vacuoles appeared to colocalize with the late endosomal GTPase, Rab7. In addition, a population of very large Rab7-positive, Rab5 Q79L-negative structures were observed, suggesting that an increase in the size of early endosomes may be accompanied by an increased size of later or more mature endocytic structures. Using antibodies against the myc epitope and the early endosomal autoantigen EEA1 as markers, we found that endosomes in wild-type and mutant MDCK cells rapidly tubulate in the presence of bafilomycin A1, an inhibitor of vacuolar H(+)-ATPase. Elongated or tubular endosomes partially colocalized with microtubules and were redistributed upon preincubation with the microtubule depolymerizing agent nocodazole before bafilomycin A1 treatment. Treatment of the Rab5 Q79L expressing cells with nocodazole alone led to a spatial redistribution and a significant decrease in the size of EEA1-positive structures, whereas their number increased. These results implicate microtubules in the bafilomycin A1-induced tubulation of endosomes as well as in the vacuolation of endosomes caused by Rab5 Q79L.

Endosomal localization of the autoantigen EEA1 is mediated by a zinc-binding FYVE finger.

EEA1, a 162-kDa autoantigen associated with subacute cutaneous systemic lupus erythematosus, is a coiled-coil protein localized to early endosomes and cytosol. At its C terminus, the protein contains a cysteine-rich motif, which is shared with Vps27, Fab1, and Vac1, yeast proteins implicated in membrane traffic (Mu, F. T., Callaghan, J. M., Steele-Mortimer, O., Stenmark, H., Parton, R. G., Campbell, P. L., McCluskey, J., Yeo, J. P., Tock, E. P., and Toh, B. H. (1995) J. Biol. Chem. 270, 13503-13511). Here we show that this motif constitutes a genuine zinc binding domain, which we term the FYVE finger (based on the first letters of four proteins containing this motif). Profile-based data base searches identified the FYVE finger in 11 distinct proteins. The FYVE finger-containing C terminus of EEA1 was found to bind 2 mol equivalents of Zn2+. Mutations of conserved histidine and cysteine residues in the FYVE motif independently reduced zinc binding to 1 mol equivalent. Confocal immunofluorescence microscopy of transfected HEp2 cells revealed that the C-terminal part (residues 1277-1411) of EEA1 colocalizes extensively with a GTPase-deficient mutant of the early endosomal GTPase Rab5, while deletion of the FYVE finger or mutations that interfere with zinc binding cause a cytosolic localization. These results implicate the FYVE finger in the specific localization of EEA1 to endosomes.

Mutations of GTBP in genetically unstable cells.

The molecular defects responsible for tumor cell hypermutability in humans have not yet been fully identified. Here the gene encoding a G/T mismatch-binding protein (GTBP) was localized to within 1 megabase of the related hMSH2 gene on chromosome 2 and was found to be inactivated in three hypermutable cell lines. Unlike cells defective in other mismatch repair genes, which display widespread alterations in mononucleotide, dinucleotide, and other simple repeated sequences, the GTBP-deficient cells showed alterations primarily in mononucleotide tracts. These results suggest that GTBP is important for maintaining the integrity of the human genome and document molecular defects accounting for variation in mutator phenotype.

GTBP, a 160-kilodalton protein essential for mismatch-binding activity in human cells.

DNA mismatch recognition and binding in human cells has been thought to be mediated by the hMSH2 protein. Here it is shown that the mismatch-binding factor consists of two distinct proteins, the 100-kilodalton hMSH2 and a 160-kilodalton polypeptide, GTBP (for G/T binding protein). Sequence analysis identified GTBP as a new member of the MutS homolog family. Both proteins are required for mismatch-specific binding, a result consistent with the finding that tumor-derived cell lines devoid of either protein are also devoid of mismatch-binding activity.

The specific subcellular localization of two isoforms of cytochrome b5 suggests novel targeting pathways.

Two forms of cytochrome b5 are present in rat tissues, with a sequence identity of approximately 60% in the cytoplasmically exposed, tryptic fragments (Lederer, F., Ghrir, R., Guiard, B., Cortial, S., and Ito, A. (1983) Eur. J. Biochem. 132, 95-102). It has been suggested that the two isoforms have partially overlapping subcellular distributions, with each form localized to some extent on both endoplasmic reticulum and outer mitochondrial membranes (Ito, A. (1980) J. Biochem. (Tokyo) 87, 73-80). To investigate the degree of specificity of the localization of cytochrome b5 isoforms, we studied their subcellular distributions with antipeptide antibodies, one specific for microsomal cytochrome b5, one specific for outer membrane cytochrome b, and one against a sequence common to the two cytochromes. We first identified outer membrane Cyt b as a tightly bound, Triton X-114-extractable, 23-kDa polypeptide. We then analyzed biochemically characterized rat liver subcellular fractions by Western blotting and found that outer mitochondrial membrane cytochrome b was not present on endoplasmic reticulum membranes. Conversely, microsomal cytochrome b5 was present on outer mitochondrial membranes in extremely low concentration, at a level < 5% of that on endoplasmic reticulum membranes. Thus, the subcellular distribution of microsomal cytochrome b5 is more restricted than previously thought, suggesting that novel posttranslational targeting mechanisms direct it to the endoplasmic reticulum.

Hodgkin's disease developing in a patient with angioimmunoblastic lymphadenopathy with dysproteinemia--a case report.

The case of a woman presenting the clinical and pathologic phenomena of angioimmunoblastic lymphadenopathy (AILD) with dysproteinemia is reported. The patient developed lesions in the lymph nodes, skin, lungs, liver and spleen, and her response to steroid and cyclophosphamide therapy was poor. At autopsy, microscopic findings in the mediastinal and abdominal lymph nodes were consistent with the diagnosis of Hodgkin's disease. Whereas the development of immunoblastic lymphoma is frequent in AILD, Hodgkin's disease is far less common. It is argued that malignant lymphoma in AILD may be the consequence of chronically depressed lymphocyte functions.