Extended Data Table 3.

Full count data for Ciona Hmx −2kb transgenic reporter analysis (Figure 2e–g) and for dCNE reporter analysis in Ciona transgenic embryos (Figure 4h).

Full count data for Ciona Hmx −2kb transgenic reporter analysis (Figure 2E–G)	Number of embryos
Tailbud stage
Total surviving	86
of which
BTN only stained	46
No stain	40
Larval stage
Total surviving	72
of which
BTN only stained	25
BTN and CNS stained	13
No stain	34
Full count data for dCNE reporter analysis in Ciona transgenic embryos (Figure 4H)
Tailbud stage
Total surviving	74
of which
BTN only stained	23
BTNs and CNS stained	29
CNS only stained	0
No stain	22
Larval stage
Total surviving	208
of which
BTN only stained	91
BTNs and CNS stained	34