title: Innervation is required for sense organ development in the lateral line system of adult zebrafish.
abstract: Superficial mechanosensory organs (neuromasts) distributed over the head and body of fishes and amphibians form the "lateral line" system. During zebrafish adulthood, each neuromast of the body (posterior lateral line system, or PLL) produces "accessory" neuromasts that remain tightly clustered, thereby increasing the total number of PLL neuromasts by a factor of more than 10. This expansion is achieved by a budding process and is accompanied by branches of the afferent nerve that innervates the founder neuromast. Here we show that innervation is essential for the budding process, in complete contrast with the development of the embryonic PLL, where innervation is entirely dispensable. To obtain insight into the molecular mechanisms that underlie the budding process, we focused on the terminal system that develops at the posterior tip of the body and on the caudal fin. In this subset of PLL neuromasts, bud neuromasts form in a reproducible sequence over a few days, much faster than for other PLL neuromasts. We show that wingless/int (Wnt) signaling takes place during, and is required for, the budding process. We also show that the Wnt activator R-spondin is expressed by the axons that innervate budding neuromasts. We propose that the axon triggers Wnt signaling, which itself is involved in the proliferative phase that leads to bud formation. Finally, we show that innervation is required not only for budding, but also for long-term maintenance of all PLL neuromasts.
authors.affiliation: Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Saitama 322-0012, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Wada
authors.forename: Christine
authors.initials: C
authors.lastname: Dambly-Chaudière
authors.forename: Koichi
authors.initials: K
authors.lastname: Kawakami
authors.forename: Alain
authors.initials: A
authors.lastname: Ghysen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism; D001483:Base Sequence; D049109:Cell Proliferation; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D017403:In Situ Hybridization; D053403:Lateral Line System / Q000254:growth & development* / Q000294:innervation*; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D019699:Thrombospondins; D014413:Tuna; D060449:Wnt Signaling Pathway / Q000502:physiology*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; C556668:RSPO1 protein, zebrafish; D019699:Thrombospondins; D029961:Zebrafish Proteins