title: Conservation, development, and function of a cement gland-like structure in the fish Astyanax mexicanus.
abstract: The larvae of the fish Astyanax mexicanus transiently develop a flat and adhesive structure on the top of their heads that we have called "the casquette" (cas, meaning "hat"). We hypothesized that the cas may be a teleostean homolog of the well-studied Xenopus cement gland, despite their different positions and structures. Here we show that the cas has an ectodermal origin, secretes mucus, expresses bone morphogenic protein 4 (Bmp4) and pituitary homeobox 1/2 (Pitx1/2), is innervated by the trigeminal ganglion and serotonergic raphe neurons, and has a role in the control and the development of the larval swimming behavior. These developmental, connectivity, and behavioral functional data support a level of deep homology between the frog cement gland and the Astyanax cas and suggest that attachment organs can develop in varied positions on the head ectoderm by recruitment of a Bmp4-dependent developmental module. We also show that the attachment organs of the cichlid Tilapia mariae larvae display some of these features. We discuss the possibility that these highly diversified attachment glands may be ancestral to chordates and have been lost repetitively in many vertebrate classes.
authors.affiliation: NeD UPR2197, Centre National de la Recherche Scientifique, Institut A. Fessard, 91198 Gif/Yvette, France.
authors.forename: Karen
authors.initials: K
authors.lastname: Pottin
authors.forename: Carole
authors.initials: C
authors.lastname: Hyacinthe
authors.forename: Sylvie
authors.initials: S
authors.lastname: Rétaux
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism; D005088:Exocrine Glands / Q000033:anatomy & histology / Q000502:physiology; D005399:Fishes / Q000033:anatomy & histology* / Q000196:embryology* / Q000235:genetics / Q000254:growth & development*; D006257:Head / Q000033:anatomy & histology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009093:Mucus / Q000378:metabolism; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism; D013550:Swimming / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D012668:Trigeminal Ganglion / Q000033:anatomy & histology; D000097577:Homeobox Protein PITX2
chemical_list: D055415:Bone Morphogenetic Protein 4; D018398:Homeodomain Proteins; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C101485:homeobox protein PITX1