FIG 1.

BRD4 is expressed in meiotic cells and spermatids but not in mature sperm. (A) Schematic of the progression of spermatogenesis beginning with meiotic cells (spermatocytes) and progressing through spermiogenesis from round to elongating to condensing spermatids. Changes in cell (tan) and nucleus (blue) size and shape are shown for reference in later figures. (B) Western blot analysis of whole-cell extracts from spermatocytes (Sc lane), round spermatids (RSp lane), elongating/condensing spermatids (E/CSp lane), a mixture of round, elongating, and condensing spermatids (R/E/CSp lane) obtained by STA-PUT velocity sedimentation, and mature sperm (Sperm lane). The asterisks mark the full-length BRD4 isoform, and the arrows indicate a novel shorter BRD4 peptide in spermatids. Peptide competition of BRD4 antibody shows the specificity of the BRD4 antibody.