Fig. 2: The retinoic acid-responsive gene Tig1 encodes a cell surface protein and is differentially expressed along the proximo-distal axis of the axolotl limb.

a Tig1 expression along the proximo-distal axis of the mature axolotl limb, relative to Ef1-α (UA upper arm, LA lower arm, H hand, qRT-PCR, n = 6 biologically independent samples). Adj. p values: *p = 0.0491, **p = 0.0068 (one-way ANOVA followed by Tukey’s multiple comparison test). b Expression of axolotl Tig1 in mature or regenerating (mid bud stage) limbs 48 h after retinoic acid (RA) treatment (100 µg/g body weight), relative to DMSO treated samples, normalised against Ef1-α expression; qRT-PCR, n = 4 (mature limb) or n = 6 (regenerating limb) biologically independent samples). **p = 0.0025 (mature limb), **p = 0.0014 (blastema) (two-tailed paired t-test). c Representative images of AL1 cells after electroporation with the indicated myc-tagged constructs and live-cell staining using anti-myc antibodies. Scale bar: 20 µm. d Microarray⁵⁴ analysis of Tig1 gene expression for the indicated bulk tissues and days post limb amputation. Note the upregulation of Tig1 during the first 7 days after amputation. Results were obtained with six independent microarray probes, each one showing the mean of three biological replicates. Note the consistent expression profile obtained with each one. e Expression of axolotl Tig1 during limb regeneration from an upper arm amputation (7.5 cm snout-to-tail axolotls) by in situ hybridisation. Representative images show blastema (upper row) or corresponding magnified area (lower row). No signal is detected in the mature limb using ISH. Scale bar: 500 µm. Each experiment was independently repeated three times with similar results (c, e). Error bars represent the standard error of the mean (SEM) (a, b). Source data are provided as a Source Data file.