Tig1 regulates proximo-distal identity during salamander limb regeneration

Abstract

Salamander limb regeneration is an accurate process which gives rise exclusively to the missing structures, irrespective of the amputation level. This suggests that cells in the stump have an awareness of their spatial location, a property termed positional identity. Little is known about how positional identity is encoded, in salamanders or other biological systems. Through single-cell RNAseq analysis, we identified Tig1/RARRES1 as a potential determinant of proximal identity. Tig1 encodes a conserved cell surface molecule, is regulated by retinoic acid and exhibits a graded expression along the proximo-distal axis of the limb. Its overexpression leads to regeneration defects in the distal elements and elicits proximal displacement of blastema cells, while its neutralisation blocks proximo-distal cell surface interactions. Critically, Tig1 reprogrammes distal cells to a proximal identity, upregulating Prod1 and inhibiting HoxA13 and distal transcriptional networks. Thus, Tig1 is a central cell surface determinant of proximal identity in the salamander limb.

Sequencing and chromosome-scale assembly of the giantPleurodeles waltlgenome

“…4a, see also Suppl. Data 6 for a general pipeline for microsynteny analysis), recently implicated in the regulation of proximo-distal identity during salamander limb regeneration (Oliveira et al, 2022). Despite clear variations in gene size, we uncovered a remarkable conservation of loci organisation, with the presence of Tig1 neighbours Schip1 and Mfsd1 at one end, and of Gfm1, Mlf1 and Shox2 at the other end of the Tig1 locus, a structure that is recapitulated across representative vertebrate genomes (Fig.…”

“…C) Tig1 overexpression affects expression of nearby genes in A. mexicanum . Bars represent ratios of gene expression in Tig1 or Tig1 P155A overexpressing cells versus control cells (analysis based on dataset from (Oliveira et al, 2022)). D) Heatmap depicting differences in gene expression of Tig1 and its genomic neighbours during P. waltl limb regeneration.…”

Retinoic Acid Receptors and the Control of Positional Information in the Regenerating Axolotl Limb

“…A more recent experiment in axolotls using a single cell sequencing dataset of connective tissue cells has identified a gene called Rarres1 (retinoic acid receptor responder 1) or Tig1 [ 37 ]. This gene is expressed in a shallow gradient in the mature limb, is upregulated by RA and is localized to the cell surface, having a transmembrane domain and a hyaluronic acid binding motif characteristic of its human homologue.…”

Senescent cells enhance newt limb regeneration by promoting muscle dedifferentiation

“…Axolotls ( A. mexicanum ) were obtained from Neil Hardy Aquatica (Croydon, UK) and from the axolotl facility at TUD-CRTD Center for Regenerative Therapies Dresden (Dresden, Germany). Animals were maintained in individual aquaria at ~18–20 °C, as previously described (Oliveira et al, 2022). Axolotls of the leucistic (d/d) strain were used in all experiments.…”