Monoclonal antibody to aldolase C: a selective marker for Purkinje cells in the human cerebellum

Maturation of Human Pluripotent Stem Cell-Derived Cerebellar Neurons in the Absence of Co-culture

The cerebellum plays a critical role in all vertebrates, and many neurological disorders are associated with cerebellum dysfunction. A major limitation in cerebellar research has been the lack of adequate disease models. As an alternative to animal models, cerebellar neurons differentiated from pluripotent stem cells have been used. However, previous studies only produced limited amounts of Purkinje cells. Moreover, in vitro generation of Purkinje cells required co-culture systems, which may introduce unknown components to the system. Here we describe a novel differentiation strategy that uses defined medium to generate Purkinje cells, granule cells, interneurons, and deep cerebellar nuclei projection neurons, that self-formed and differentiated into electrically active cells. Using a defined basal medium optimized for neuronal cell culture, we successfully promoted the differentiation of cerebellar precursors without the need for co-culturing. We anticipate that our findings may help developing better models for the study of cerebellar dysfunctions, while providing an advance toward the development of autologous replacement strategies for treating cerebellar degenerative diseases.

Neurotrophins and their Trk-receptors in the cerebellum of zebrafish

Neurotrophins (NTs) and their specific Trk-receptors are key molecules involved in the regulation of survival, proliferation, and differentiation of central nervous system during development and adulthood in vertebrates. In the present survey, we studied the expression and localization of neurotrophins and their Trk-receptors in the cerebellum of teleost fish Danio rerio (zebrafish). Teleostean cerebellum is composed of a valvula, body and vestibulolateral lobe. Valvula and body show the same three-layer structure as cerebellar cortex in mammals. The expression of NTs and Trk-receptors in the whole brain of zebrafish has been studied by Western blotting analysis. By immunohistochemistry, the localization of NTs has been observed mainly in Purkinje cells; TrkA and TrkB-receptors in cells and fibers of granular and molecular layers. TrkC was faintly detected. The occurrence of NTs and Trk-receptors suggests that they could have a synergistic action in the cerebellum of zebrafish. J. Morphol. 277:725-736, 2016. © 2016 Wiley Periodicals, Inc.

Identification of an anti-aldolase autoantibody as a diagnostic marker for diabetic retinopathy by immunoproteomic analysis

Circulating autoantibodies specific for retinal proteins are associated with retinal destruction in patients with diabetic retinopathy (DR). In this study, we screened diabetic sera for the presence of anti-retinal autoantibodies with an aim of developing diagnostic markers for DR. Immunoblot analysis of DR patients' sera with human retinal cytosolic proteins revealed a higher incidence of anti-retinal autoantibodies, compared to normal blood donors or diabetic patients without DR. Anti-retinal protein autoantibody profiles of DR patient sera were obtained by 2-DE immunoblot analysis. Specifically, 20 protein spots reactive with DR patient sera were identified by ESI-MS/MS. Of these spots, 14 were specific for DR patients, and 4 reacted with both non-proliferative DR (non-PDR) and PDR sera. The anti-aldolase autoantibody was selected as a DR marker candidate, and specific reactivity of DR patient sera was confirmed by immunoblot analysis with rabbit aldolase. The serum anti-aldolase autoantibody level was measured by ELISA. DR patients showed significantly higher autoantibody levels than normal donors or diabetic patients without retinopathy. However, no significant differences were observed between non-PDR and PDR patients, suggesting that the level of anti-aldolase autoantibody is not determined by the severity of retinopathy in diabetic patients. Our data collectively demonstrate that the anti-aldolase autoantibody serves as a useful marker for DR diagnosis.

Role of isozyme group-specific sequence 4 in the isozyme-specific properties of human aldolase C

To assess which regions of the aldolase C molecule are required for exhibiting isozyme-specific kinetic properties, we have constructed nine chimeric enzymes of human aldolases A and C. Kinetic studies of these chimeric enzymes revealed that aldolase C absolutely required its own isozyme group-specific sequences (IGS), particularly IGS-4, for exhibiting the characteristics of aldolase C which differ significantly from those of isozymes A and B (Kusakabe T, Motoki K, Hori K. Human aldolase C: characterization of the recombinant enzyme expressed in Escherichia coli. J Biochem (Tokyo) 1994;115:1172-7). Whereas human aldolases A and B required their own isozyme group-specific sequences-1 and -4 (IGS-1 and -4) as the main determinants of isozyme-specific kinetic properties (Motoki K, Kitajima Y, Hori K. Isozyme-specific modules on human aldolase A molecule. J Biol Chem 1993;268:1677-83; Kusakabe T, Motoki K, Sugimoto Y, Takasaki Y, Hori K. Human aldolase B: liver-specific properties of the isoenzyme depend on type B isozyme group-specific sequence. Prot. Eng. 1994;7:1387-93), the present studies indicate that the IGS-1 is principally substitutable between aldolases A and C. The kinetic data also suggests that the connector-2 (amino acid residues 243-306) may modulate the interaction of IGS units with the alpha/beta barrel of the aldolase molecule.

Genomic sequences of aldolase C (Zebrin II) direct lacZ expression exclusively in non-neuronal cells of transgenic mice

Aldolase C is regarded as the brain-specific form of fructose-1, 6-bisphosphate aldolase whereas aldolase A is regarded as muscle-specific. In situ hybridization of mouse central nervous system using isozyme-specific probes revealed that aldolase A and C are expressed in complementary cell types. With the exception of cerebellar Purkinje cells, aldolase A mRNA is found in neurons; aldolase C message is detected in astrocytes, some cells of the pia mater, and Purkinje cells. We isolated aldolase C genomic clones that span the entire protein coding region from 1.5 kb 5' to the transcription start site to 0.5 kb 3' to the end of the last exon. The bacterial gene, lacZ, was inserted in two different locations and the constructs tested in transgenic mice. When the protein coding sequences were replaced with lacZ, three of five transgenic lines expressed beta-galactosidase only in cells of the pia mater; one line also expressed in astrocyte-like cells. When lacZ was inserted into the final exon (and all structural gene sequences were retained) transgene expression was observed in astrocytes in all regions of the central nervous system as well as in pial cells. Thus, with the exception of Purkinje cell expression, the behavior of the full-length transgene mimics the endogenous aldolase C gene. The results with the shorter transgene suggest that additional enhancer elements exist within the intragenic sequences. The absence of Purkinje cell staining suggests that the cis elements required for this expression must be located outside of the sequences used in this study.

Mode of interactions of human aldolase isozymes with cytoskeletons

Three isoforms of fructose-1,6-bisphosphate aldolase were found to bind specifically to the actin-containing filament of the cytoskeleton and to show tissue-specific binding patterns. Aldolase A (muscle type) bound more tightly to the skeletal muscle cytoskeleton among the three isozymes, while aldolase B (liver type) preferred the liver cytoskeleton to those of other tissues. The specific binding of aldolase A to the skeletal muscle cytoskeleton was inhibited strongly by the substrates fructose 1,6-bisphosphate and fructose 1-phosphate. Several mutant aldolases A were examined to identify the amino acid residues or regions that play a role in specific binding. Among the mutant aldolases tested, A-E34D, A-K41N, and A-Y363S exhibited remarkably reduced binding activities. Experiments using FITC-labeled enzymes and Rh-labeled phalloidin disclosed that aldolase A associated with the cytoskeleton. Specifically, when aldolase A was incubated with human fibroblast MRC-5 permeabilized with Triton X-100, aldolase A bound to the actin filaments in the stress fibers within the cell. Aldolase A reversibly inhibited the contraction of MRC-5 cells which usually occurred in the presence of Mg2(+)-ATP and Ca2+. These results provide direct evidence that aldolase binds specifically to the actin-containing stress fibers and suggest that aldolase may regulate cell contraction through its reversible binding to the filaments in the permeabilized MRC-5 fibroblast.

Aldolase C/zebrin II and the regionalization of the cerebellum

The cerebellum is comprised of multiple bands of cells, each with characteristic afferent and efferent projections, and patterns of gene expression. The most studied example of a striped pattern of expression is the antigen recognized by monoclonal antibody antizebrin II. Zebrin II is expressed by subsets of Purkinje cells that form an array of parasagittal bands that extend rostrocaudally throughout the cerebellar cortex, separated by similar bands of Purkinje cells that do not express zebrin II. Recent cloning studies have revealed that the zebrin II antigen is the respiratory isoenzyme aldolase C. This article reviews the cellular and molecular compartmentation of the cerebellum together with the molecular biology of the aldolase C gene, and speculates on possible reasons for a striped pattern of expression.

The cloning of zebrin II reveals its identity with aldolase C

The sagittal organization of the mammalian cerebellum can be observed at the anatomical, physiological and biochemical level. Previous screening of monoclonal antibodies produced in our laboratory has identified two intracellular antigens, zebrin I and II, that occur exclusively in adult cerebellar Purkinje cells. As their name suggests, the zebrin antibody staining of the Purkinje cell population is not uniform. Rather, zebrin-positive Purkinje cells are organized in stripes or bands that run from anterior to posterior across most of the cerebellum; interposed between the zebrin-positive cells are bands of Purkinje cells that are zebrin-negative. Comparison of the position of the antigenic bands with the anatomy of afferent projections suggests that the bands are congruent with the basic developmental and functional ‘compartments’ of the cerebellum. We report the isolation of cDNA clones of the 36 × 10(3) M(r) antigen, zebrin II, by screening of a mouse cerebellum cDNA expression library. Sequence analysis reveals a 98% identity between our clone and the glycolytic isozyme, aldolase C. In order to more rigorously demonstrate the identity of the two proteins, we stained adult cerebellum with an independent monoclonal antibody raised against aldolase C. Anti-aldolase staining occurs in a previously unreported pattern of sagittal bands of Purkinje cells; the pattern is identical to that revealed by the zebrin II monoclonal. Further, in situ hybridization of antisense aldolase C riboprobe shows that the accumulation of zebrin II/aldolase C mRNA corresponds to the pattern of the zebrin antigen in Purkinje cells. Zebrin II/aldolase C gene expression is thus regulated at the level of transcription (or mRNA stability). In light of previous work that has demonstrated the cell-autonomous and developmentally regimented expression of zebrin II, further studies of the regulation of this gene may lead to insights about the determination of cerebellar compartmentation.

Cytoplasmic expression of the leu-4 (CD3) antigen in developing Purkinje cells in the rat cerebellum

Although commonly known to represent a T cell receptor (CD3) associated polypeptide, the leu-4 (CD3) antigen occurs in cerebellar Purkinje cells (PCs) of many species. The monoclonal pan T lymphocyte marker anti-leu-4 (CD3) recognizes both the lymphocytic and the Purkinje cell type of this antigen [22]. To obtain more information about the merit of anti-leu-4 (CD3) as an investigational tool, we evaluated the expression of leu-4 (CD3) in PCs of the developing rat cerebellum (in situ) by light microscopy. Positive anti-leu-4 (CD3) immunoreaction of PCs did not occur prior to post-natal day (D) 4. The analysis of immunostaining during cell differentiation revealed three major phases of post-natal PC maturation including antigenic development of cell somata (phase 1: until D6), dendrites (phase 2: D7-D11), and axons (phase 3: D12-D14). A massive post-weaning expansion of the dendritic arborization led then to the mature PC architecture. Additionally, the leu-4 (CD3) antigen was observed in ectopic PC dendrites (D10) and in ectopic (mature) PCs. Throughout post-natal development as well as in mature PCs, the leu-4 (CD3) antigen was found to be cytoplasmic. Due to its labile nature, neither an ultrastructural localization nor molecular characterization could be achieved. For the same reason, its application is basically restricted to cryo-fixed cerebellar tissue. However, at the level of light microscopy, the monoclonal human T cell marker anti-leu-4 (CD3) proved to be a useful tool for specific and sensitive labelling of differentiated cerebellar PCs in the rat.

Immunolocalization of cathepsin D in the human central nervous system and central nervous system neoplasms

The cellular distribution of the lysosomal proteinase cathepsin D was studied in a series of 76 neoplasms and 18 non-neoplastic tissues from the human central nervous system, using a well-characterized polyclonal antibody in a peroxidase-antiperoxidase technique. In the normal and developing brain, cathepsin D is confined to neurons and choroid plexus epithelium. Strong granular cytoplasmic staining was present in neuronal and choroid plexus neoplasms, and in reactive macrophages. A large variety of other neoplasms also exhibited positive cytoplasmic staining, albeit usually of a weaker diffuse type. Cathepsin D cannot be considered a specific marker for neuronal or choroid plexus neoplasms, but the antiserum used in this study may be of value in antibody panels for the investigation of these tumours. Its localization may also be of value in embryological studies, particularly in the cerebellum, and in investigations of steroid hormone receptor-associated proteins in meningiomas and Schwannomas.

Development of the cerebellum with particular reference to cellular differentiation in the external granular layer

Immunocytochemical evidence of differentiation in developing human cerebellum is presented in this study. Antibodies to neuron specific enolase, neurofilament protein, glial fibrillary acidic protein, vimentin, cytokeratin, epithelial membrane antigen and lymphoid markers, DLC and Leu 7 were used. The external granular layer showed positivity with neuronal markers between 27 weeks gestation and 4 months postnatal, but was negative for all other markers including glial fibrillary acidic protein. Characteristic staining reactions were noted in the other cerebellar layers. Monoclonal antibodies, UJ13A (pan-neuroectodermal marker) and G10 (localising microtubule-associated protein MAP1x) were also used in a limited number of cryostat sections and were positive and negative, respectively, in the external granular layer. The results of this study are discussed in relation to the theory that the external granular layer may be one source of medulloblastomas.

Lhermitte-Duclos disease. An immunohistochemical study of the cerebellar cortex

Immunocytochemical studies were carried out on two previously reported autopsy cases of Lhermitte-Duclos disease. The unaffected cerebellar cortex adjacent to the lesions served as control. The findings supported the view, previously expressed by one of the authors, of a heterogeneous neuronal structure of the lesion, consisting of at least two cell types. No further light was thrown on the predominant medium-sized cells, believed to represent hypertrophic internal granular neurons. On the other hand the large cells shared a number of features with Purkinje cells. In particular they were recognized by the pan-T-cell antibody anti-Leu-4, were surrounded by axosomatic synapses visualized by the antisynaptic vesicle glycoprotein antibody SV2, and contained both non-phosphorylated and phosphorylated neurofilament epitopes. It is suggested that these cells represent dysplastic Purkinje cells. The lesion therefore appears to be a complex hamartoma rather than a simple hypertrophy of the internal granular neurons.

Stromal cells in cerebellar haemangioblastomas: an immunocytochemical study

The nature of the stromal cells in formalin-fixed paraffin-embedded material from 23 cerebellar haemangioblastomas was investigated using antisera to intermediate filaments (glial fibrillary acidic protein, vimentin and desmin), histiocytic markers (alpha 1-antitrypsin, alpha 1-antichymotrypsin and lysozyme), glycolytic enzymes (alpha and gamma enolase and aldolase C4) and the endothelial markers, factor VIII related antigen and Ulex europaeus I lectin. Most stromal cells stained positively for vimentin and the glycolytic enzymes. Occasional process-bearing cells within the stroma stained strongly for glial fibrillary acidic protein, alpha 1-antitrypsin and alpha 1-antichymotrypsin. No stromal cell staining for desmin, lysozyme or the endothelial markers was observed, although the latter stained the vascular endothelium within all neoplasms. The findings do not support previous suggestions of an endothelial or histiocytic origin for the stromal cells. They appear to be a heterogeneous population including entrapped reactive astrocytes and locally-derived non-angiogenic cells of neuroectodermal (pial) origin.