Urp1 and Urp2 are two neuropeptides of the urotensin II family identified in teleost fish and mainly expressed in cerebrospinal fluid (CSF)-contacting neurons. It has been recently proposed that Urp1 and Urp2 are required for correct axis formation and maintenance. Their action is thought to be mediated by the receptor Uts2r3, which is specifically expressed in dorsal somites. In support of this view, it has been demonstrated that the loss of
uts2r3
results in severe scoliosis in adult zebrafish. In the present study, we report for the first time the occurrence of
urp2,
but not of
urp1
, in two tetrapod species of the
Xenopus
genus. In
X. laevis
, we show that
urp2
mRNA-containing cells are CSF-contacting neurons. Furthermore, we identified
utr4,
the
X. laevis
counterparts of zebrafish
uts2r3,
and we demonstrate that, as in zebrafish, it is expressed in the dorsal somatic musculature. Finally, we reveal that, in
X. laevis,
the disruption of
utr4
results in an abnormal curvature of the antero-posterior axis of the tadpoles. Taken together, our results suggest that the role of the Utr4 signalling pathway in the control of body straightness is an ancestral feature of bony vertebrates and not just a peculiarity of ray-finned fishes.
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