Fig. S3

Ablation of chordoblasts does not impair overall notochord integrity.

(A,B) Lateral view of an untreated (A; n=42) and a Mtz treated Tg(col2a1a:CFP-NTR) transgenic larva (B; n=63) at 8dpf, anterior is to the left. Even though the chordoblast ablated animal is a bit shorter than the untreated control, it has an obvious notochord (arrow) and an infladed swim bladder, indicating that it does not suffer from retarded development. Panels (C,D) depict magnifications of a stretch of notochord of the same specimens as in (A,B). As in the untreated larva (C), vacuolated notochordal cells persist after chordoblast ablation upon Mtz incubation from 4dpf to 6.5dpf (D). (E,F) TEM micrographs of transverse sections at the level of chordacentra through the notochordal sheath and adjacent chordoblast layer in an untreated control Tg(col2a1a:CFP-NTR) (D; n=5) and an Mtz-treated specimen of the same genotype (F; n=6) at 8dpf. The shown chordoblast (cb) of the untreated control (E) contains an intact nucleus (*) and clearly recognizable rER (arrow), and is directly attached to a proximally positioned notochordal cell (ncc). In the chordoblast-ablated larva (F), no distinct chordoblasts can be found; rather material without any obvious cellular structures designated as “undefined cellular debris” (ucd) can be detected at cognate positions. Underscoring the acellular nature of this material, no directly attached notochordal cells can be observed (**). It is most likely this ucd that gives rise to the remaining rather weak uniform fluorescence seen around the notochord of chordoblast-ablated larvae (compare with Fig.4C,D). Scale bars correspond to 500μm in (A,B), 100μm in (C,D) and 0.5μm in (E,F). Other abbreviations: ns, notochord sheath.