Actin accumulation in developing chick brain and other tissues

Cytoplasmic actin isolated from chick brain tissue was identified by electron microscopy, myosin-binding ability, SDS and urea gel analysis, and tryptic peptide mapping. Tissue actin levels were measured from SDS-polyacrylamide gels of brain, heart, lens, liver, and skin tissue homogenates from 5- to 20-day chick embryos and from 17-week-old adults. Actin levels were highest in 11- to 13-day embryo brains. This time span is coincident with the most active period of neuron differentiation and axonal growth cone activity. Actin levels were generally higher in nonmuscle tissues of the embryo than of the adult, supporting the concept that actin is involved in cell motility during tissue morphogenesis. However, low levels of actin maintained in some adult nonmuscle tissues (brain, liver, and skin) suggest a role for cytoplasmic actin in physiological functions other than cell motility.