Cell cycle synchrony in the developing chicken lens epithelium.

Synchronous oscillations of DNA synthesis and histone 2B mRNA expression occur during normal development of 13- to 16-day-old embryonic chicken lens epithelium. At least four cycles were observed with peak values of DNA synthesis and histone 2B mRNA 5 to 10 times greater than baseline values. Fourier analysis of DNA synthesis identified a statistically significant oscillatory period of 18 hr, the approximate length of the cell cycle at this age. Minor components of 7-9 and 12 hr were also identified in the data sets. Lenses labeled with 3H-thymidine and analyzed by autoradiography at 13.8 days of embryogenesis revealed more than twice the number of labeled nuclei at this time than in lenses labeled 9 hr later; histone 2B mRNA followed this same pattern. These findings demonstrate that a significant population of cells is synchronized with respect to the cell cycle in the developing lens epithelium in ovo. The temporal pattern of mitosis may be the basis of the fiber cell architecture and consequent lens transparency.