FIG. 4.
Anatomical and histological defects in the heterozygotes. (a, a′, b, and b′) Skeletal preparations of two-month-old Brd4+/Brd4+ (a) and Brd4gt/Brd4+ (b) male skulls, respectively; bone is stained in red and cartilage in blue. Note the shorter and bent nasal bone (arrow), the shorter incisor bone (arrowhead), and the shorter mandible of the heterozygote. f, frontal bone; i, incisive bone; ip, interparietal bone; lf, lacrimal foramen; m, mandible; mp, mastoid process; n, nasal bone; o, occipital bone; os, orbital surface of the frontal bone; p, parietal bone; t, temporal bone; tb, tympanic bulla; z, zygomatic bone. (c and d) Sections through the skin of two Brd4+/Brd4+ (c) and Brd4gt/Brd4+ (d) 1-month-old individuals. In the heterozygote, the epidermis (e) was thickened and the amount of subcutaneous adipose tissue (s) was reduced and contained degenerating adipose cells surrounded by phagocytic cells (black arrow). d, dermis; m, muscle. (e and f) Sections through the liver of two Brd4+/Brd4+ (e) and Brd4gt/Brd4+ (f) 2-month-old individuals. The black arrow in Fig. 4f points to degenerating hepatocytes, and the white arrowheads point at surrounding phagocytes in the heterozygote.