Ectopic Expression of NCAM in Mouse Fibroblasts Stimulates Self-aggregation,and Promotes Integration into Primary Cerebellum Cell Aggregates

We have undertaken aggregation experiments using mouse LMTK-fibroblasts transfected with various isotypes of the neural cell adhesion molecule, NCAM. We found that selfaggregation of NCAM-positive fibroblasts is enhanced compared to control-transfected cells. The aggregation properties are partly dependent on the expressed NCAM isotype. Fibroblasts expressing a NCAM 140 isotype with exons a₃ and π were further tested in primary cerebellum cell re-aggregation experiments. While control-transfected fibroblasts could not be found in forming aggregates, fibroblasts ectopically expressing NCAM were integrated into neural cell aggregates. Time-lapse photography indicated that the nascent primary cell aggregates actively participated in the integration process by migration and attachment to nearby NCAM-positive fibroblasts.