Reissner's fibre promotes neuronal aggregation and influences neuritic outgrowth in vitro.

Reissner's fibre is the condensed form of glycoproteins secreted by the subcommissural organ; it extends through the central canal to the caudal end of the spinal cord. The effect of Reissner's fibre was assessed on dissociated embryonic chick cortical neuronal cells grown in chemically defined medium, by using two cell culture systems: (1) low-density cultures, in which neuronal cells remained evenly distributed; (2) high-density cultures, in which neuronal cells aggregated, displaying prominent neuritic outgrowth. Reissner's fibre, when added to low-density cultures, induced neuronal aggregation and neuritic outgrowth but this effect was restricted to an area centred around Reissner's fibre. Reissner's fibre, when added to high-density cultures, potentiated cell aggregation. Antibodies inhibiting the neural cell adhesion molecule or N-cadherin, and soluble Reissner's fibre material (reported previously to have anti-aggregative activity), did not prevent the aggregative activity induced by Reissner's fibre. Neuronal cells showed a similar reaction pattern when heparin or Reissner's fibre was added to the culture. These results suggest that the subcommissural organ/Reissner's fibre complex has multifunctional activities and may modulate cell-cell interactions during the development of the central nervous system.