Article Dans Une Revue General and Comparative Endocrinology Année : 2026

Characterization and expression of urotensin1 and urotensin2 genes in the caudal neurosecretory system of the small-spotted catshark Scyliorhinus canicula

Résumé

A C T The caudal neurosecretory system (CNSS) is a neuroendocrine complex unique to fish. In teleosts, the neuroendocrine neurons of the CNSS, called Dahlgren cells, are located in the terminal part of the spinal cord and project to a neurohemal organ, the urophysis, from which several hormones are released. The two major hormones secreted by Dahlgren cells are two neuropeptides called urotensin 1 (UI), related to the corticotropinreleasing hormone and urotensin 2 (UII), related to somatostatin. In cartilaginous fishes, the CNSS organization is simpler than in teleosts due to the absence of urophysis. As a consequence, Dahlgren cells project into a diffuse neurohemal region located at the ventral base of the spinal cord. Such an organization of the CNSS is considered as primitive. An important feature of Dahlgren cells in cartilaginous fishes is also their huge size. The goal of the present study was to provide more insight into the CNSS in cartilaginous fish, which has been poorly studied so far. For this purpose, we used the small-spotted catshark Scyliorhinus canicula, as a model. We first cloned the cDNAs encoding for both catshark UI (uts1) and UII (uts2). This search revealed the existence of two copies of the uts1 gene, uts1a and uts1b, that are tandemly arranged. We then determined by RT-qPCR the expression pattern of the uts1a, uts1b, and uts2 genes in various catshark tissues. Our results revealed that uts1a and uts2 genes are primarily expressed in giant cells of the caudal spinal cord, that likely correspond to Dahlgren cells. The uts1a transcript was also detected in the epididymis head of the testis but at a much lower level. In contrast, the uts1b transcript was detected at very low levels in all tissues examined. Further study by double fluorescence in situ hybridization showed that in the caudal spinal cord, all uts1a mRNA-containing cells expressed uts2 while only about half of the uts2-expressing cells also expressed uts1a. Taken together these results suggest the existence of two populations of Dahlgren cells: one of which expressing solely uts2 and the other expressing both uts1a and uts2. In conclusion, our work showed that, as in teleosts, uts1 and uts2 are two potentially useful markers for studying the CNSS in cartilaginous fish.

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Dates et versions

hal-05408431 , version 1 (02-02-2026)

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Bérénice Bichon, Gladys Alfama, Anne-Laure Gaillard, Feng B Quan, Pascal Sourdaine, et al.. Characterization and expression of urotensin1 and urotensin2 genes in the caudal neurosecretory system of the small-spotted catshark Scyliorhinus canicula. General and Comparative Endocrinology, 2026, 376, pp.114866. ⟨10.1016/j.ygcen.2025.114866⟩. ⟨hal-05408431⟩
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