Ultrastructural examination of megakaryocytes derived from BACH1 transgenic mice. Panels show electron micrographs of megakaryocytes derived from the bone marrow of a wild-type littermate (A; original magnification × 4000) and a transgenic mouse (B; original magnification × 4000). Megakaryocytes derived from the transgenic mouse exhibited insufficient demarcation membrane formation and had a decreased number of cytoplasmic α granules. Yellow arrowheads indicate the demarcation membrane in megakaryocytes from a wild-type littermate.