Quantitation of delta-crystallin messenger RNA during lens induction in chick embryos.

Authors:
  • TST Shinohara
    T Shinohara
  • JPJ Piatigorsky
    J Piatigorsky
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Abstract
Embryonic chick cells of the presumptive lens ectoderm are induced to differentiate into a lens by the optic vesicle, an outgrowth from the developing brain. This lens induction involves formation of the lens placode by cell elongation between about 44 and 50 h of development, followed by invagination of the placode between about 50 and 55 h of development. The amount of .delta.-crystallin messenger RNA (mRNA) in heads of embryos between 48 and 72 h of development was determined by molecular hybridization with [3H]DNA complementary to purified .delta.-crystallin mRNA. An average of approximately 0.5 pg of .delta.-crystallin mRNA was found per embryonic head at 48 h of development. This leads to approximately 265 molecules of .delta.-crystallin mRNA per lens cell, if one assumes that the mRNA is confined to the lens rudiment, as is indicated by immunofluorescence studies of .delta.-crystallin performed by other investigators. Pulse-labeling experiments with [35S]methionine indicated that the .delta.-crystallin mRNA is being translated already at this time. .delta.-Crystallin mRNA accumulated at an average rate of 1 molecule/cell per min. between 48 and 72 h of development. Thus, by extrapolation, the initiation of .delta.-crystallin mRNA accumulation coincides with the initiation of lens placode formation of approximately 43-44 h of development, which is some 8-9 h after the initiation of lens induction by the optic vesicle. The .delta.-crystallin synthesis is regulated by the accumulation of .delta.-crystallin mRNA during lens induction in chick embryos.

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