The mechanism of aggregation of neural retina cellsin vitro.

1. The mechanism of aggregation of dissociated embryonic neural retina cells was investigated during a period of 24 hoursin vitro, and was found to consist of two distinct phases. The first phase depended on the residual cell surface material after trypsinization and was largely insensitive to cycloheximide. The second phase was sensitive to cycloheximide, indicating dependence on protein synthesis. 2. The rate of aggregation during the first hour was not eliminated by suppression of the endogenous energy source nor affected by added exogenous ATP or ADP. 3. Intercellular retina protein (I.R.P.) was isolated from neural retina tissues by EDTA treatment. The maximum rate of aggregation occurred in cultures containing 100 μg protein/ml. One μg of isolated protein was able to aggregate approximately 17000 retina cells. The process of aggregation by I.R.P. was found to be sensitive to cycloheximide. 4. I.R.P. attachment appeared to be dependent on the availability of a receptive layer on the surface of the dissociated retina cells. 5. Evidence obtained in these experiments suggested that retina cell aggregation after 24 hours depended on biosynthesis, and that macromolecules (protein or glycoprotein) were required for cell aggregation. 6. The molecular basis of cell aggregation and its role in morphogenesis is discussed.