Serum factors affecting transdifferentiation in chick embryo neuro-retinal cultures

Adult sera (horse, chicken and newborn bovine serum) do not support extensive transdifferentiation of lens cells in cultures of 9-day chick embryo neural retina. Conversely, both chick embryo extract and foetal calf serum promote the accumulation of delta-crystallin (a marker for lens cells) in such cultures. Dialysed foetal calf serum does not allow transdifferentiation into lens, whereas the dialysis medium is able to do so in the absence of macromolecular serum components, suggesting one or more active factors of low molecular weight. Choline acetyltransferase activity (cholinergic neuronal marker) is generally maintained for longer under conditions which do not permit extensive transdifferentiation. Glutamine synthetase activity (a glial marker) is inducible by hydrocortisone in dense neuro-retinal cultures, and this hormone also reduces the extent of later lens development.