Fig. 5.

Expression pattern of Hau-cif4 during Helobdella development. A Within the germinal plate mesoderm, Hau-cif4 expression was first detected in a pair of cells or cell clusters in each of the four rostral segments (open arrowheads) and at lower levels in two bilateral pairs of cells in the prostomium (asterisk) in mid stage 8 (anterior ventral view). Note the posterior extension of the segmental Hau-cif4-expressing cell clusters (magenta arrowheads). B In mid-to-late stage 8 (anterior ventral view), the Hau-cif4 expressing cell clusters (open arrowheads) assume tubular forms. The ventral midline ectoderm also starts to express Hau-cif4 (white arrow). C Enlarged view of boxed area in B, showing a single row of Hau-cif4-expressing cells (yellow arrowheads; two cells per segment) aligning along the ventral midline. D In early stage 9, expression of Hau-cif4 declines in lateral rostral segmental mesoderm (open arrowheads) and begins in the nephridial primordia in the midbody segmental mesoderm (black arrowheads). Hau-cif4 expression in the ventral midline ectoderm persists (white arrow). E Enlarged view of the boxed area in D, showing two rows of Hau-cif4-expressing cells (8–10 cells per segment) in the ventral midline ectoderm at this stage. F In mid stage 9 (lateral view), Hau-cif4 is expressed in the complete set of developing nephridia (numbered to indicate midbody segmental identity), glial cells in the dorsal anterior (yellow arrow) and segmental ganglia (white arrows), and ventral side of the anterior midgut (cyan arrow). G Ventral view of the same embryo shown in F. Nephridial tubules (green arrowheads) connecting the nephridia to the bodywall also express Hau-cif4. H Close-up view of the ventral midbody region of a stage 10 embryo, where Hau-cif4 expression is associated with neuropil of segmental ganglia (yellow arrowheads), the connective nerve (red arrowheads), and more diffusely within the segmental ganglia (blue arrowheads). Scale bar: 120 µm (A,B,D,F,G); 20 µm (C,E); 80 µm (H).