Nerve Growth Factor Receptor (NGFR/p75NTR) of the Small‐Spotted Catshark (<i>Scyliorhinus canicula</i>): Evolutionary Conservation and Brain Function

The p75NTR receptor, a member of the tumor necrosis factor (TNF) receptor superfamily, can participate in signaling pathways either by forming heteromeric complexes with other receptors, such as the Trk family (tropomyosin receptor kinases), or by functioning independently. p75NTR was investigated prevalently in the brain and retina of mammals, whereas almost nothing is known about its conservation among species. Here, we reconstructed the phylogenetic arb of p75NTR and described for the first time the p75NTR expression in the brain of the basal vertebrate Chondrichthyan Scyliorhinus canicula (S. canicula), uncovering the existing parallelism between ancient vertebrates and mammals. p75NTR functional conservation among vertebrates was further investigated by cloning the S. canicula nerve growth factor (NGF) and performing the canonical posterior commissure (PC)-12 differentiation assay, which results in standard neurite-like production. We then investigated the S. canicula p75NTR, which proves to be capable of complementing a specific clone of PC-12 lacking p75NTR (PC-12 p75NTR^-/^-). All together, our results highlighted the expression and functional conservation of p75NTR among vertebrates during the evolution.