CONTROLLED PRODUCTION OF PROLIFERATING SOMATIC CELL HYBRIDS

The techniques described permit the controlled production of large numbers of proliferating somatic cell hybrids in a relatively short period of time. Sendai virus is used to promote cell hybridization. β-propriolactone is employed as the inactivating agent of Sendai virus since it produces complete loss of viral infectivity while preserving viral fusion capacity. Cells are fused in monolayer, instead of in suspension, since fixing cells in two dimensions permits one to control cell contacts during the fusion event through the expedient of varying multiplicities of the parental cells and the total cell density. Under the conditions described, a several hundred fold increase in the number of hybrid clones obtained is seen as compared to the controls

Somatic cell genetic analysis of the interferon system : (interferon genetics, interferon receptors , cell hybrids )

The interferon system is amenable to somatic cell genetic analysis since the genes governing the synthesis of interferon and the cellular responses to interferon can be expressed in tissue culture cells. Limited species specificity exists in the interferon system, allowing interspecific hybrid cells to be used in mapping genes involved in interferon production and mechanism of action. The synthesis of interferon and the attainment of the antiviral state following interferon treatment are separate genetic functions, governed by genes on different chromosomes. Three different human chromosomes have been implicated in the production of human fibroblast interferon based on studies using interspecific somatic cell hybrids. The recent cloning of multiple interferon gene sequences will provide probes for further gene mapping. Genes governing sensitivity of cells to interferon have been mapped to human chromosome 21 and mouse chromosome 16. When human/mouse somatic cell hybrids are injected into mice of the same strain as the murine parent of the hybrid, antibodies directed against cell surface components coded by the retained human chromosomes are produced. Antibodies raised against human chromosome 21-coded cell surface determinants can block human interferon action on human fibroblasts, presumably by blocking a human interferon receptor. Monoclonal antibodies against this receptor can be produced and used to study the role of receptors in interferon action.DORIS L . SLATE and FRANK H. RUDDLE, Department of Biology, Yale University, New Haven, CT

Expression of Liver Phenotypes in Cultured Mouse Hepatoma Cells

Mouse hepatoma cells were established in vitro as a permanently growing line designated Hepa. The mass population and a subclone were characterized for their karyotype and their retention of liver-specific properties. An examination of 17 hepatic traits revealed that the cell lines secreted several serum proteins. The activities of a number of liver-specific enzymes, however, appeared to be absent in these cells. The identification of differentiated properties of cultured hepatoma cells permits the use of these lines in a variety of studies such as cell hybridization, biochemical analysis of tissue-specific gene products, and the modulation of expression of genes governing differentiated phenotypes. This report presents the analysis of a broad spectrum of characteristics and thereby describes one of the most fully defined hepatoma cell lines of murine origin in the literatur

Evidence for independent Hox gene duplications in the hagfish lineage: a PCR-based gene inventory of Eptatretus stoutii

Hox genes code for transcription factors that play a major role in the development of all animal phyla. In invertebrates these genes usually occur as tightly linked cluster, with a few exceptions where the clusters have been dissolved. Only in vertebrates multiple clusters have been demonstrated which arose by duplication from a single ancestral cluster. This history of Hox cluster duplications, in particular during the early elaboration of the vertebrate body plan, is still poorly understood. In this paper we report the results of a PCR survey on genomic DNA of the pacific hagfish Eptatretus stoutii. Hagfishes are one of two clades of recent jawless fishes that are an offshoot of the early radiation of jawless vertebrates. Our data provide evidence for at least 33 distinct Hox genes in the hagfish genome, which is most compatible with the hypothesis of multiple Hox clusters. The largest number, seven, of distinct homeobox fragments could be assigned to paralog group 9, which could imply that the hagfish has more than four clusters. Quartet mapping reveals that within each paralog group the hagfish sequences are statistically more closely related to gnathostome Hox genes than with either amphioxus or lamprey genes. These results support two assumptions about the history of Hox genes: (1) The association of hagfish homeobox sequences with gnathostome sequences suggests that at least one Hox cluster duplication event happened in the stem of vertebrates, i.e., prior to the most recent common ancestor of jawed and jawless vertebrates. (2) The high number of paralog group 9 sequences in hagfish and the phylogenetic position of hagfish suggests that the hagfish lineage underwent additional independent Hox cluster/-gene duplication events

The Shark HoxN Cluster is Homologous to the Human HoxD Cluster

The statistical analysis of phylogenetic footprints in the two known horn shark Hox clusters and the four mammalian clusters shows that the shark HoxN cluster is HoxD-like. This finding implies that the most recent common ancestor of jawed vertebrates had at least four Hox clusters, including those which are orthologous to the four mammalian Hox clusters