THE EXPRESSION OF TROPOMYOSIN GENES IN PURE CULTURES OF RAT NEURONS, ASTROCYTES AND OLIGODENDROCYTES IS HIGHLY CELL-TYPE SPECIFIC AND STRONGLY REGULATED DURING DEVELOPMENT

Transcripts from the alpha-, beta- and delta-tropomyosin genes were studied during development of pure cultures of rat neurons. astrocytes and oligodendrocytes. The three cell types contained five alpha-tropomyosin messengers, produced using both alternative promoters and splicing; one was specific for mature neurons. The beta-tropomyosin gene is expressed only in astrocytes and the delta-tropomyosin gene in all three cell types, especially in immature cells. Most of the tropomyosin isoforms are highly cell-specific. Their developmental regulation involves either differential expression of genes, in neurons and oligodendrocytes, and/or changes in alternative splicing, in astrocytes. Delta-tropomyosin (TM-4) may be important during the growth of neuronal and glial cell processes, while specialized isoforms such as the neuron-specific a-tropomyosin TMBr-3 may be involved in the function or plasticity of the mature cells.