title: Photoreceptor differentiation in cerebellar medulloblastoma: evidence for a functional photopigment and authentic S-antigen (arrestin).
abstract: The aim of the present study was to evaluate the putative photoreceptor differentiation found in certain cerebellar medulloblastomas. The analyses were focussed on S-antigen, rod-opsin (the apoprotein of the visual pigment rhodopsin) and 11-cis retinal (the prosthetic group of rhodopsin). Fresh frozen and paraffin-embedded biopsy specimens of three medulloblastomas were investigated by means of immunocytochemistry, enzyme-linked immunosorbent assay (ELISA), high-pressure liquid chromatography (HPLC), and immunoblotting. As shown in paraffin sections, one out of the three tumors (tumor A) contained S-antigen- and rod-opsin-immunoreactive tumor cells. The immunoblotting technique revealed in this tumor a single protein band of approximately 48-50 kDa that reacted with the S-antigen antibody and three protein bands of approximately 40, 75 and 110 kDa recognized by the rod-opsin antibody. These bands could not be detected in the two remaining tumors (tumor B and C). The rod-opsin content of tumor A was quantified by the ELISA; 11.7 pmol rod-opsin were calculated for the biopsy. The HPLC demonstrated the presence of 11-cis- and all-trans-retinal in tumor A, but not in tumors B and C. Furthermore, it was shown that 11-cis-retinal was converted to all-trans-retinal upon illumination of the tumor extract. The ratio between 11-cis- and all-trans-retinal was approximately 1:1 before illumination and 3:5 after illumination. A total of 2-3 pmol of retinal was found in the biopsy of tumor A. In addition all-trans-retinol was present in this tumor. The results indicate that certain medulloblastomas express a functional photopigment and S-antigen, another protein of the phototransduction cascade. They strongly support the concept that medulloblastoma cells may differentiate along the photoreceptor cell lineage.
authors.affiliation: Institut für Anatomie und Zytobiologie, Giessen, Federal Republic of Germany.
authors.forename: C M
authors.initials: CM
authors.lastname: Kramm
authors.forename: H W
authors.initials: HW
authors.lastname: Korf
authors.forename: M
authors.initials: M
authors.lastname: Czerwionka
authors.forename: W
authors.initials: W
authors.lastname: Schachenmayr
authors.forename: W J
authors.initials: WJ
authors.lastname: de Grip
mesh_terms: D000941:Antigens / Q000032:analysis*; D019393:Arrestin; D015153:Blotting, Western; D002528:Cerebellar Neoplasms / Q000473:pathology*; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D008527:Medulloblastoma / Q000473:pathology*; D010786:Photoreceptor Cells / Q000473:pathology / Q000502:physiology*; D010858:Pigmentation / Q000502:physiology*; D012172:Retinaldehyde / Q000032:analysis; D012243:Rhodopsin
chemical_list: D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins; D012243:Rhodopsin; D012172:Retinaldehyde