Study of the nature of the growth-inhibiting factor in embryos of mice of the mutant line brachypodism-H.

An extract from 13-day embryos of mice homozygous with respect to the bp-H gene contains a growth-inhibiting factor (GIF), which inhibits the growth of normal bones in vitro. The activity of the GIF depends on the concentration of the extract in the culture medium. The sensitivity of the GIF to heating and proteolytic enzymes is an indication of its protein nature. The precipitation of the GIF from the embryonic extract with ammonium sulfate, followed by fractionation on columns with Sephadex G-200 and DEAE-Sephadex gave a 400-fold degree of purification. The active growth-inhibiting preparation obtained is represented by three proteins, which migrate slowly in electrophoresis in polyacrylamide gel. The molecular weight of the basic component is 76,000.