Histone variant patterns during vertebrate embryogenesis and limb development

Two-dimensional gel electrophoresis was used to examine the relative content of core histone variants during early chicken embryogenesis and at selected stages of hindlimb development. Nuclei from stage 19 limb buds displayed a pattern similar to whole embryos at stage 1, at which time all of the known avian histone variants, including the minor isoprotein H3.3, were detected. Variant ratios did not change during limb development, up to stage 29. However, the portion of H2A variants migrating as ubiquitinated conjugates increased more than twofold during limb development, advancing from 4.5% of the total H2A proteins at stage 19 to 12% at stage 29.