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Abstract

The time of appearance and histological localization of the crystallins, especially the lens-fiber specific γ crystallins, in the normally developing lens of Xenopus laevis were determined by immunofluorescence techniques. Antibodies to total soluble lens proteins as well as to purified γ crystallins were applied to sections through the eye region of X. laevis embryos, Nieuwkoop-Faber Stages 23–45. Seven stages of lens development, the earliest highly atypical, were recognized in this species. The first positive immunofluorescence reaction for both the anti-total and anti-γ crystallin antibodies occurred at Lens Developmental Stage 3. At this time the lens rudiment is irregular and flattened, with a slightly-condensed central mass of cells. These centrally located cells, probably prospective primary lens fiber cells, are positive for γ crystallins, while both they and surrounding retinally-oriented lens cells are positive for total lens crystallins. This general immunofluorescence profile continues during lens development, with only the lens fiber areas positive for γ crystallins. No reaction with either antibody type, however, could be detected in the corneally-oriented external layer or, later, the lens epithelium, until very late in the development of the lens (Nieuwkoop-Faber Stage 45). The lack of crystallins in this cell type, together with the transitory appearance of a lens vesicle (lens cavity), delayed until after fiber cells have been formed, sets X. laevis morphological and biochemical lens development apart from that of other vertebrates.