Figure 2: Expression of catecholamine biosynthetic enzymes by lamprey sympathoblasts.

(a-j) HCR detection of Th (teal) and Dbh (red) in lamprey at T28. Co-localization of the transcripts is seen in cells surrounding the heart (b-d) and spanning the initial length of the trunk in bilateral streams (e-j). Scale bars=100μm. n=15 embryos across five independent replicates. (k-m) Immunohistochemical detection of TH (teal) at T28 is consistent with HCR. HNK1 antibody staining of axons is shown in red. Scale bars=100μm. n=15 embryos across five independent replicates. (n, o) Immunohistochemical detection of TH (red) at (n) T27 and (o) ammocete stages. At both stages, TH+ cells are localized lateral to the dorsal aorta (denoted by white asterisks) and dorsal to the yolk tube or the intestinal epithelium. TH+ cells are highlighted in zoomed insets. DAPI is shown in white. Scale bars=50μm. n=12 embryos, 12 ammocetes across four independent replicates.