Role of the hindbrain in patterning the otic vesicle: a study of the zebrafish vhnf1 mutant.
The vertebrate inner ear develops from an ectodermal placode adjacent to rhombomeres 4 to 6 of the segmented hindbrain. The placode then transforms into a vesicle and becomes regionalised along its anteroposterior, dorsoventral and mediolateral axes. To investigate the role of hindbrain signals in instructing otic vesicle regionalisation, we analysed ear development in zebrafish mutants for vhnf1, a gene expressed in the caudal hindbrain during otic induction and regionalisation. We show that, in vhnf1 homozygous embryos, the patterning of the otic vesicle is affected along both the anteroposterior and dorsoventral axes. First, anterior gene expression domains are either expanded along the whole anteroposterior axis of the vesicle or duplicated in the posterior region. Second, the dorsal domain is severely reduced, and cell groups normally located ventrally are shifted dorsally, sometimes forming a single dorsal patch along the whole AP extent of the otic vesicle. Third, and probably as a consequence, the size and organization of the sensory and neurogenic epithelia are disturbed. These results demonstrate that, in zebrafish, signals from the hindbrain control the patterning of the otic vesicle, not only along the anteroposterior axis, but also, as in amniotes, along the dorsoventral axis. They suggest that, despite the evolution of inner ear structure and function, some of the mechanisms underlying the regionalisation of the otic vesicle in fish and amniotes have been conserved.
Lecaudey
Virginie
V
Unité de Biologie du Développement, CNRS UMR 7622, Université Pierre et Marie Curie, Paris, France.
Ulloa
Encarna
E
Anselme
Isabelle
I
Stedman
Aline
A
Schneider-Maunoury
Sylvie
S
Pujades
Cristina
C
D000818:Animals; D007758:Ear, Inner / Q000196:embryology* / Q000378:metabolism; D051537:Hepatocyte Nuclear Factor 1 / Q000378:metabolism*; D017403:In Situ Hybridization; D009024:Morphogenesis / Q000502:physiology*; D010590:Phalloidine; D012249:Rhombencephalon / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics
D051537:Hepatocyte Nuclear Factor 1; D010590:Phalloidine