Comparative genomic in situ hybridization discloses recurrent gain of chromosome 4 in experimental gliomas of the rat.

The genetic characterization of experimental tumors is essential in order to evaluate their relevance as appropriate animal models for human neoplasms. We have used flow cytometry and a recently established Comparative Genomic in situ Hybridization (CGH) protocol for the rat (Kappler et al., 1998) to investigate chromosome copy number changes in five ethylnitrosourea induced gliomas of the rat. Flow cytometry showed aneuploid DNA indices in three of the tumors investigated. CGH analysis of primary tumors revealed whole chromosome and subchromosomal gains of rat chromosomes (RNO) 1, 2, 4, 6, 7, 10, 11, 12, and 13. Loss of RNO 5q23-->q35 was apparent in one tumor. High level copy number gains were not observed using CGH as well as semiquantitative PCR with Tgfa, Met and Hbb primers. Low copy number gain of RNO 4 represents the most common aberration, since it was detected in four of five tumors investigated. Three tumors showed gain of RNO 7, while two tumors showed gains of RNO 10q31-->qter and RNO 12q. Deletion of RNO 5q23-->q35 and gain of RNO 4 occurred mutually exclusively. Therefore, we conclude that these two alterations may represent different pathways in the pathogenesis of experimental gliomas in the rat. Findings are discussed in analogy to human gliomas.     

C-banding of Peromyscus constitutive heterochromatin persists following histone hyperacetylation

Approx. 35% of the DNA of cultured cells from the cactus mouse, Peromuscus eremicus, is contained in highly condensed constitutive heterochromatin which can be visualized in metaphase chromosomes stained by the C-band technique. Previous studies have shown this constitutive heterochromatin to contain a large proportion of underacetylated, arginine-rich histones, the majority of which can be hyperacetylated when cells are treated with butyrate. In order to determine whether this simulation of the acetylated state of euchromatin alters the cytological properties of constitutive heterochromatin as well, chromosomes from butyrate-treated cells have been examined. Because of the paucity of cells in butyrate-treated cultures, prematurely condensed chromosomes (PCCs) were produced from butyrate-treated cells by fusion with mitotic cells. In these PCCs, both the highly condensed nature and the ability to C-band were preserved in the hyperacetylated constitutive heterochromatin, suggesting that the subset of arginine-rich histones which is refractory to acetylation in the presence of butyrate may be responsible for the maintenance of the heterochromatic state. In addition, PCC analyses indicated that butyrate arrests Peromyscus cells in both the G1 and G2 phases of the cell cycle and confirmed the late-replicating pattern of constitutive heterochromatin.     

Bemerkungen zu: Dr. E. Hesse, Erg?nzungen etc

Ohne Zusammenfassung

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Altered erythrocyte protein kinase C activity and membrane protein phosphorylation in chronic myelogenous leukemia

The membrane protein kinase C (PKC) content was found to be higher in erythrocytes form patients suffering from chronic myelogenous leukemia (CML) compared to normal erythrocytes. PKC activity was also higher in the cytosol and after translocation to the membrane, as assessed by histone phosphorylation. The increased PKC activity in CML erythrocytes was associated with abnormal phosphorylation of protein 4.1. Since phosphorylation-dephosphorylation mechanisms are likely candidates for controlling membrane protein associations, the altered PKC activity may be one of the factors responsible for altered thermal sensitivity and mechanical stability of CML erythrocytes.