Loss of heterozygosity on chromosome 9 and loss of chromosome 9 copy number are separate events in the pathogenesis of transitional cell carcinoma of the bladder.

The most frequent genetic aberration found in transitional cell carcinoma (TCC) of the bladder involves chromosome 9. Loss of heterozygosity (LOH) analyses show deletions of both chromosome 9p and 9q, while in situ hybridization studies suggest a significant percentage of tumours with monosomy 9. To investigate the types of chromosome 9 losses that occur in bladder cancer, we have studied 40 tumours with different techniques such as in situ hybridization (ISH), flow cytometry and LOH analysis. LOH for one or more markers was found in 43% of the tumours. This percentage does not differ from previous reports. With ISH, complete monosomy for chromosome 9 was observed in only 1 of the 40 tumours. Four other tumours had monosomic subpopulations, representing 23-40% of the cells. In 18 cases, an underrepresentation of the chromosome 9 centromere relative to chromosome 6 or to the ploidy of the tumour was observed, including the cases with monosomy. In 5 of these 18 cases, the relative loss could not be confirmed by LOH. In addition, when LOH and a relative underrepresentation were observed in the same tumour, the extent of LOH as measured by the intensity of allele loss, was often not related to the extent of underrepresentation. We therefore conclude that complete monosomy of chromosome 9 is rare in TCCs of the bladder and that a relative loss of centromere signal may not be related to a loss compatible with inactivation of a tumour suppressor gene. LOH was found in TCCs of all stages and grades. Our results suggest that loss of tumour suppressor genes on chromosome 9 is an early event in the pathogenesis of bladder cancer.

Neurofibromatosis type 2 protein co-localizes with elements of the cytoskeleton.

The product of the neurofibromatosis type 2 (NF2) tumor suppressor gene is a 595-amino-acid protein bearing resemblance to a family of band-4.1-related proteins. These proteins, including ezrin, radixin, and moesin, probably function as molecular linking proteins, connecting the cytoskeleton to the cell membrane. On the grounds of the homology to the ezrin, radixin, and moesin proteins and on the basis of its predicted secondary structure, the NF2 protein is also thought to act as a cytoskeleton-cell membrane linking protein. Using monoclonal antibodies to amino- and carboxyl-terminal synthetic NF2 peptides we demonstrate the co-localization of the NF2 protein with elements of the cytoskeleton in a COS cell model system and in cultured human cells. Furthermore, the presence of the NF2 protein in tissue sections is shown. The monoclonal antibodies specifically stain smooth muscle cells and the stratum granulosum of the human epidermis. In cultured smooth muscle cells the NF2 protein co-localizes with actin stress fibers. Immunoelectron microscopy demonstrates the presence of the NF2 protein associated with keratohyalin granules and to a lesser extent with intermediate filaments in the human epidermis. We conclude that the NF2 protein is indeed associated with multiple elements of the cytoskeleton.

The biological activity of interferon alpha is influenced by two distinct regions in the protein.

With the aim to assign differences in activity between murine interferon-alpha 1 and -alpha 4 to specific amino acids, we have constructed hybrid genes and analysed the antiviral properties of the corresponding hybrid proteins. The hybrid genes were constructed by means of homologous recombination between the alpha 1 and alpha 4 genes in Escherichia coli. Hybrids in which the N-terminal part is derived from alpha 1 show that two regions have a major effect on the activity: amino acid 10-20 and 55-67. When comparing hybrids with N-terminal alpha 4 sequences, transitions in activity are found in the same regions. Interestingly, the curves for the two sets of hybrids are exactly each others mirror image.

Interferon expression in the testes of transgenic mice leads to sterility.

A plasmid containing the mouse interferon-alpha 1 gene under control of the mouse metallothionein-I promoter was used for the construction of transgenic mice. Four transgenic mice (two males and two females) were obtained containing 1 to over 10 copies of the introduced DNA. Both males appeared to be sterile. One of the female mice founded a transgenic strain in which the foreign DNA was transmitted to her offspring in a Mendelian fashion. In this strain most male animals are sterile or turn sterile with time. Northern blot analysis of several tissues of these animals shows that expression of the introduced interferon gene occurs only in the testis. In some of the animals biologically active interferon could also be detected in testes homogenates. Histological examination of testis tissue shows an ongoing degeneration of spermatogenic cells leading to calcium deposits and complete atrophy of the seminiferous tubules.