Fig. 4

Apoptosis in sensory organs and brain regions. (A–C) Transverse sections through inner ear at 36 hpf (A, B) and 60 hpf (C); dorsal is up and lateral is left. (A) The anterior macula and the statoacoustic ganglion contained apoptotic cells at 36 hpf. (B) The posteromedial macula also contained apoptotic cells at 36 hpf. (C) The semicircular canal and posterior macula contained apoptotic cells at 60 hpf. (D) Lateral view of 36 hpf whole mount; anterior is left and dorsal is up. Apoptosis in the trigeminal ganglion (arrow), anterior lateral line ganglion (arrowhead) and otocyst (asterisk). (E–H) Brain region apoptosis in transverse sections; dorsal is up in all panels. (E) At 48 hpf, apoptotic cells in the telencephalon were frequently located adjacent to the olfactory placode, in the region where ingrowing axons terminate. (F) Apoptotic cells at 48 hpf in the pineal gland (arrow). (G) Hypothalamus at 60 hpf. Throughout development, numerous apoptotic cells (arrows) were observed in the hypothalamus. (H) Tectum and tegmentum of the midbrain. At 60 hpf, the tectum contained numerous apoptotic cells, often clustered symmetrically (arrows) but also as single cells (arrowheads). Apoptotic cells in the tegmentum were less frequent (asterisk). Abbreviations: am, anterior macula; di, diencephalon; ol, otolith; oo, olfactory organ; pm, posteromedial macula; sag, statoacoustic ganglion; sc, semicircular canal; tec, tectum; teg, tegmentum; tel, telencephalon. Scale bars in (A), 25 mm for (A) and (B); in (C), 25 μm for (C), (E), and (F); in (D), 25 μm for (D), (G), and (H).