Antibodies for immunolabeling by light and electron microscopy : not for the faint hearted

Reliable antibodies represent crucial tools in the arsenal of the cell biologist and using them to localize antigens for immunocytochemistry is one of their most important applications. However, antibody-antigen interactions are much more complex and unpredictable than suggested by the old 'lock and key' analogy, and the goal of trying to prove that an antibody is specific is far more difficult than is generally appreciated. Here, we discuss the problems associated with the very complicated issue of trying to establish that an antibody (and the results obtained with it) is specific for the immunolabeling approaches used in light or electron microscopy. We discuss the increasing awareness that significant numbers of commercial antibodies are often not up to the quality required. We provide guidelines for choosing and testing antibodies in immuno-EM. Finally, we describe how quantitative EM methods can be used to identify reproducible patterns of antibody labeling and also extract specific labeling distributions.Peer reviewe

Chromogranin A in the olfactory system of the rat

The olfactory bulb of the rat contains chromogranin A at a similar level as the adrenal gland or the hypophysis as revealed by immunoblots. Olfactory chromogranin A also displays the same size as chromogranin A of endocrine cells. In the hippocampus and other brain regions, we could not detect chromogranin A by immunoblotting. In contrast, chromogranin A messenger ribonucleic acid (using S1 nuclease protection assays) was observed in all brain regions examined, including the olfactory bulb. By in situ hybridization histochemistry with a complementary ribonucleic acid probe (280 nucleotides), and by immunocytochemistry, chromogranin A synthesis could be localized to cell bodies of the mitral cell layer, of the external plexiform layer and of the periglomerular region of the olfactory bulb. Immunocytochemically, chromogranin A was also detected in the central projection areas of mitral and tufted cells in the primary olfactory cortex and the anterior amygdaloid area but not in the olfactory glomeruli, where the incoming olfactory nerve fibers of the primary olfactory neurons establish synaptic contacts. Taken together the data show that chromogranin A, following biosynthesis in the perikarya of the mitral and tufted cells, is specifically transported into their axonal terminals but not into their primary dendrites. We propose that the rat olfactory system could serve as a model for the study of chromogranin A regulation and function in neurons

Cultured microvascular endothelial cells derived from the bovine corpus luteum possess NCAM-140

Previously, five phenotypically different, stable types of microvascular endothelial cells (MVE) were isolated from the bovine corpus and cultured successfully. We found that three out of these five types of MVE express the neural cell adhesion molecule (NCAM). As shown by immunocytochemistry, weak NCAM immunoreactivity occurred mainly in the perinuclear area of cell type 1. Monolayers of types 2 and 5 revealed heavy NCAM immunoreactivity, which was localized predominantly at the lateral cell surface outlining the contact zones of adjacent cells. In contrast, cell types 3 and 4 were not NCAM immunoreactive. Western blot analyses substantiated these results: While cell type 1 showed a weak immunoreactive band, cell types 2 and 5 displayed strong NCAM-immunoreactive bands of a molecular weight of approximately 140 kDa (NCAM-140), which was absent in cell types 3 and 4. These results reveal for the first time that NCAM can be expressed by cultured MVE and may serve in mediating endothelial cell contacts. Since luteal cells also express NCAM-140, this adhesion molecule could in addition be involved in the interactions of luteal cells with MVE

CRISPR-Cas9 screens in human cells and primary neurons identify modifiers of C9ORF72 dipeptide-repeat-protein toxicity.

Hexanucleotide-repeat expansions in the C9ORF72 gene are the most common cause of amyotrophic lateral sclerosis and frontotemporal dementia (c9ALS/FTD). The nucleotide-repeat expansions are translated into dipeptide-repeat (DPR) proteins, which are aggregation prone and may contribute to neurodegeneration. We used the CRISPR-Cas9 system to perform genome-wide gene-knockout screens for suppressors and enhancers of C9ORF72 DPR toxicity in human cells. We validated hits by performing secondary CRISPR-Cas9 screens in primary mouse neurons. We uncovered potent modifiers of DPR toxicity whose gene products function in nucleocytoplasmic transport, the endoplasmic reticulum (ER), proteasome, RNA-processing pathways, and chromatin modification. One modifier, TMX2, modulated the ER-stress signature elicited by C9ORF72 DPRs in neurons and improved survival of human induced motor neurons from patients with C9ORF72 ALS. Together, our results demonstrate the promise of CRISPR-Cas9 screens in defining mechanisms of neurodegenerative diseases

Ontogeny of synaptophysin and synaptoporin in the central nervous system

The expression of the synaptic vesicle antigens synaptophysin (SY) and synaptoporin (SO) was studied in the rat striatum, which contains a nearly homogeneous population of GABAergic neurons. In situ hybridization revealed high levels of SY transcripts in the striatal anlage from embryonic day (E) 14 until birth. In contrast. SO hybridization signals were low, and no immunoreactive cell bodies were detected at these stages of development. At E 14, SY-immunoreactivity was restricted to perikarya. In later prenatal stages of development SY-immunoreactivity appeared in puncta (identified as terminals containing immunostained synaptic vesicles), fibers, thick fiber bundles and ‘patches’. In postnatal and adult animals, perikarya of striatal neurons exhibited immunoreaction for SO; ultrastructurally SO antigen was found in the Golgi apparatus and in multivesicular bodies. SO-positive boutons were rare in the striatum. In the neuropil, numerous presynaptic terminals positive for SY were observed. Our data indicate that the expression of synaptic vesicle proteins in GABAergic neurons of the striatum is developmentally regulated. Whereas SY is prevalent during embryonic development, SO is the major synaptic vesicle antigen expressed postnatally by striatal neurons which project to the globus pallidus and the substantia nigra. In contrast synapses of striatal afferents (predominantly from cortex, thalamus and substantia nigra) contain SY

FNA based diagnosis of head and neck nodal lymphoma [Citomorfološka dijagnoza limfoma u području glave i vrata]

Fine-needle aspiration (FNA) biopsy has become a well established technique in the diagnosis, staging, and follow-up of patients with head and neck lesions. As in lymphoma diagnostics, FNA serves as a screening method in evaluating potentially affected lymph node for open or core biopsy. According to the World Health Organization classification of lymphoid neoplasms, today it is important to recognize cell morphology and reveal its phenotype, then combine it with different genotypic information and clinical data to provide appropriate therapy. The aim of this study was to assess the efficacy of FNA and immunocytochemistry based lymphoma diagnostic in head and neck region. We conducted a retrospective study during a period of three years where cases with either FNA diagnosis or clinical suspicion of newly recognized or relapsing lymphoma were reviewed. In the study were included patients that were referred to our laboratory from hematology department, in whom head and neck lymphadenopathia was found and lymph node FNA preceded other procedures. Two hundred eighty-five aspirations from 248 patients fulfilled study criteria. Adequate specimens were diagnosed as lymphoma in 100 cases (36%), in 65 male and 35 female patients, 76 in patients with newly discovered disease and 24 in patients with prior lymphoma diagnosis. Overall sensitivity of FNA specimens in the diagnosis of head and neck lymphomas was 90%, specificity 88%, predictive value of a positive result 97%, and predictive value of negative result 61%. Based on our results FNA corroborated with immunophenotyping by immunocytochemistry can be method of choice in primary lymphoma diagnosis as a method complementary to histopathology in lymphoma diagnostics

Endocrine cells share expression of N-CAM with neurones

The reeent explosive interest in eell adhesion molecules (CAMs) is a direet eonsequence of the fundamental roles they are thought to play during early embryogenesis and tissue formation [1,2]. The most weIl known of them, studied independently under the names of N-CAM [3] (neural-CAM), 02 protein [4] and BSP-2 [5], has been shown to consist in brain of a family of three glyeoproteins of Mr 180000, 140000 and 120000 [6,7] which are implicated in neurone-neurone adhesion by a homophilie binding meehanism [8,9]. While N-CAM was originally considered to be limited to neurones in adult tissues, ultrastruetural immunoeytochemical studies have sinee provided unequivocal evidenee that glial cells, both astrocytes [6,10] and Schwann cells [11], also express N-CAM (see also [12,13]). Apart from a very limited expression by skeletal muscle at the neuromuscular junetion [14], its expression in the adult Correspondence address: O.K. Langley, Unite 44 de I'INSERM, and Centre de Neurochirnie du CNRS, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France has been largely though not exclusively considered to be limited to nervous tissues. N-CAM has been found in eertain eells outside the nervous system (e.g. chromaffin eells in the adrenal medulla [11]) but such eells are derived from the neural crest. Here we extend our previous observations on endocrine eells in the adrenal gland and investigate the possible expression of N-CAM by other endoerine eells whieh have a non-neural origin. The present results indieate a mueh wider distribution of N-CAM in adult tissues than has previously been supposed. N-CAM is shown by immunoeytoehemistry to be expressed by several endoerine eells of non-neural origin. Immunoehemieal data eonfirm the presenee of N-CAM determinants typical of brain in endoerine eells although the relative proportions differ markedly. In addition, in two of the tissues examined a lower molecular mass NCAM positive polypeptide was also detected