An early global role for Axin is required for correct patterning of the anterior-posterior axis in the sea urchin embryo

Activation of Wnt/β-catenin (cWnt) signaling at the future posterior end of early bilaterian embryos is a highly conserved mechanism for establishing the anterior-posterior (AP) axis. Moreover, inhibition of cWnt at the anterior end is required for development of anterior structures in many deuterostome taxa. This phenomenon, which occurs around the time of gastrulation, has been fairly well characterized but the significance of intracellular inhibition of cWnt signaling in cleavage-stage deuterostome embryos for normal AP patterning is less well understood. To investigate this process in an invertebrate deuterostome we defined Axin function in early sea urchin embryos. Axin is ubiquitously expressed at relatively high levels in early embryos and functional analysis revealed that Axin suppresses posterior cell fates in anterior blastomeres by blocking ectopic cWnt activation in these cells. Structure-function analysis of sea urchin Axin demonstrated that only its GSK-3β-binding domain is required for cWnt inhibition. These observations and results in other deuterostomes suggest that Axin plays a critical conserved role in embryonic AP patterning by preventing cWnt activation in multipotent early blastomeres, thus protecting them from assuming ectopic cell fates.

Deorphanization of ORL-1/LC132 by reverse pharmacology in two landmark studies

Deorphanization of ORL-1/LC132 in 1995 by reverse pharmacology in two simultaneously published landmark studies added a new member to the opioid family of G-protein coupled receptors. Meunier and Reinscheid used cells expressing recombinant ORL-1 (human) or LC132 (rat) and the presumed intracellular inhibition of cyclic AMP formation to ‘fish’ for endogenous peptide ligands in rat whole-brain and pig hypothalamic extracts. Both studies reported the isolation of a 17-amino-acid peptide, which was named nociceptin and orphanin FQ by the two authors, respectively. The behaviour of the isolated peptide was a complete surprise, as a general hyperalgesia was observed when the peptide was administered at supraspinal sites. We now know that this peptide has, in fact, anti-opioid action, particularly in the medulla. The endogenous peptide exerts a multitude of effects both in the nervous system and, unlike classical opioids, has efficacy in neuropathic pain.