Ethical standards--Part Two.
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American Medical Association↗
Biomedical subjects
S J Keating
Publications and source records attributed to S J Keating.
Skeletal muscle arises as a late event during development of wound sarcomas in v-jun transgenic mice.
Mice carrying an H-2K-v-jun transgene develop malignant sarcomas by a multistage mechanism following wounding. Here we show that these malignancies are often heterogeneous in composition, containing both undifferentiated mesenchymal cells as well as focal areas of skeletal muscle. Such myogenic areas are not detectable in premalignant precursor lesions, suggesting that cells competent for muscle differentiation arise at a late stage of tumorigenesis. Immunohistochemical staining of transgenic sarcomas reveals that levels of v-Jun correlate inversely with muscle-specific gene expression, suggesting that high levels may be inhibitory to myogenesis. Consistent with this idea, we demonstrate that whereas high levels of v-Jun are able to block MyoD-dependent gene expression in vitro, the levels of v-Jun in sarcoma-derived myogenic cells are below the threshold required to produce this effect. The cell of origin of v-jun wound sarcomas, as well as the relationship between myogenic determination and multistage tumorigenesis, are discussed in the light of these results.
Actins↗
Obligatory wounding requirement for tumorigenesis in v-jun transgenic mice.
Avian sarcoma virus 17 induces fibrosarcomas in chickens and can transform a number of avian cell types in vitro by the action of v-jun. This gene and the related cellular genes c-jun, jun B and jun D, encode transactivating (or repressing) DNA-binding proteins that form homo- or heterodimeric (Jun-Jun and Jun-Fos) complexes which recognize the AP-1 consensus sequence TGACTCA, a response element that confers sensitivity to the tumour-promoting phorbol ester TPA. We have produced several lines of transgenic mice carrying the v-jun oncogene, driven by the promoter of the widely expressed H-2KK major histocompatibility complex (MHC) class I antigen gene. Transgenic animals are initially phenotypically normal, but after full-thickness wounding they show abnormal wound repair, characterized by hyperplastic granulation tissue. Many of these lesions are slowly progressive because of continuing fibroblast proliferation, and over 2-5 months some give rise to dermal fibrosarcomas. This reproducible multistep transition through a proliferative but benign intermediate is associated with characteristic increments in v-jun expression. Moreover, hyperplastic wound repair and its progression are both related to transgene dosage, suggesting that there exists a quantitative requirement or threshold for v-jun action. Our results indicate that v-jun is not oncogenic in transgenic mice as a result of a 'single-hit' mechanism, but rather, in addition to an obligatory wound, that secondary genetic or epigenetic events (possibly conscripting normal constituents of wound repair) are necessary for tumour development and progression.
Animals↗
Short rib polydactyly syndrome type I: an autopsy approach to diagnosis of chondrodysplasias.
The autopsy diagnosis of neonates with chondrodysplasias is often difficult due to the rarity of many of these conditions and to a complex classification scheme. Accurate diagnosis is essential for counseling of parents with one or more affected infants. Classification is currently based on radiological appearances and gross morphology. Following examination of two siblings with short rib polydactyly syndrome (SRPS) type I, we undertook to analyze the main problems in clinical pathological classification of chondrodysplasias. The problems identified are: variability in the constellations of morphological features that are used for diagnosis; insufficient radiological data being obtained at the time of autopsy; failure to preserve tissue appropriately for the necessary studies and lack of knowledge of the underlying abnormalities in most chondrodysplastic syndromes. It is anticipated that biochemical and molecular genetic abnormalities will eventually be discovered to reduce diagnostic uncertainty in the chondrodysplasias. Presently the diagnostic process is facilitated when frozen tissue is available for studies such as collagen, proteoglycan, and enzyme analysis and mRNA and DNA analyses.
Cartilage, Articular↗