Determination of Chick Neuro-retinal Cells in Culture: Serum Factors Acting between 12 and 20 Days of Culture Influence the Extent of Subsequent Lens Cell Formation

Embryonic chick neuroretinal cells transdifferentiate into lens cells during culture in media containing foetal calf serum (F). This process is largely inhibited if horse serum plus supplementary glucose (Hg) is substituted for F. This paper explores the effect of medium changeover (from F to Hg or vice versa ) on the subsequent appearance of lens-specific δ-crystallin. If cultures are changed from Hg to F up to 12 days of culture, δ-production at 40 days is similar to that for controls maintained in F throughout. Changeovers between 14 and 17 days progressively inhibit subsequent δ production, and after 19 days in Hg, lens transdifferentiation cannot be induced by F. Conversely, if cultures are maintained in F for up to 17 days, a changeover to Hg blocks transdifferentiation, whereas similar transfers performed after 19 days give increased δ production. These results suggest that some retinal cells which will eventually form lens in vitro become so determined between the 12th and 20th days of culture. A mixture of 50% Hg and 50% F medium (FHg) does not support δ production even after 60 days, but in the absence of supplementary glucose (FH), δ appears in considerable amounts by 30 days.