The cellular basis of myosin heavy chain isoform expression during development of avian skeletal muscles |
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| Authors: | F E Stockdale J B Miller |
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| Affiliation: | 1. Stanford School of Medicine, Department of Medicine, Stanford, California 94305-5306 USA;2. Stanford School of Medicine, Department of Biology, Stanford, California 94305-5306 USA;1. The State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China;2. College of Animal Science and Technology, China Agricultural University, Beijing 100193, China;3. Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Biological Science, China Agricultural University, China;1. Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia;2. BU 4/3, 47800 Petaling Jaya, Selangor, Malaysia;1. Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK;2. BioMar Ltd., Grangemouth Docks, Grangemouth FK3 8UL, UK;3. Institute of Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan, ROC |
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| Abstract: | Many pluripotent embryonal carcinoma (EC) cell lines and all embryonic stem (ES) cell lines have hitherto been maintained in the undifferentiated state only by culture on feeder layers of mitomycin C-treated embryonic fibroblasts. We now demonstrate that medium conditioned by incubation with Buffalo rat liver (BRL) cells prevents the spontaneous differentiation of such cells which occurs when they are plated in the absence of feeders. This effect is not mediated via cell selection but represents a fully reversible inhibitory action ascribed to a differentiation-inhibiting activity (DIA). BRL-conditioned medium can therefore replace feeders in the propagation of homogeneous stem cell populations. Such medium also restricts differentiation in embryoid bodies formed via aggregation of EC cells and partially inhibits retinoic acid-induced differentiation. The PSA4 EC line gives rise only to extraembryonic endoderm-like cells when aggregated or exposed to retinoic acid in BRL-conditioned medium. This suggests that DIA may be lineage-specific. DIA is a dialysable, acid-stable entity of apparent molecular weight 20,000-35,000. Its actions are reproduced neither by insulin-like growth factor-II nor by transforming growth factor-beta. DIA thus appears to be a novel factor exerting a negative control over embryonic stem cell differentiation. |
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