DNA-POLYMERASES IN MOUSE SPERMATOGENIC CELLS SEPARATED BY SEDIMENTATION-VELOCITY

Activity levels of DNA polymerase α and DNA polymerase β have been measured in mouse spermatogenic cells separated by sedimentation velocity. Testes from prepuberal (17 day old) and sexually mature mice were dissociated and separated by unit gravity sedimentation into 6 populations of cells. Phase contrast microscopy and [3H]thymidine labeling kinetics revealed that at least 85% of the cells in fraction A were pachytene-stage primary spermatocytes, fraction B was enriched for primary spermatocytes and round spermatids, fraction C contained spermatogonia and/or pre-leptotene primary spermatocytes and later stages of spermatids (no spermatids were present in fraction C from the testes of 17 day old mice) and fractions D to F contained mixed populations of cells, many in later stages of spermiogenesis. When expressed as activity in 106 cells or as a specific activity, fractions A, B, and C from mature animals contained substantially higher levels of DNA polymerases α and β than the cell population initially loaded onto the gradient while fractions D, E and F had activity levels similar to or below the population of dissociated cells. The ratio of activity between the DNA polymerases was constant in fractions A, B, and C, but in fractions D, E, and F, the ratio decreased due to a more rapid decline of activity of polymerase α. A comparison of activity levels in fraction C from prepuberal and sexually mature mice revealed an increase in DNA polymerase α activity and a decrease in the activity of DNA polymerase β in the cells from the 17 day old animals. © 1979.