The evolution of asymmetric photosensitive structures in metazoans and the Nodal connection

Abstract : Asymmetries are observed in a great number of taxa in metazoans. More particularly, functional lateralization and neuroanatomical asymmetries within the central nervous system have been a matter of intense research for at least two hundred years. While asymmetries of some paired structures/organs (e.g. eyes, ears, kidneys, legs, arms) constitute random deviations from a pure bilateral symmetry, brain asymmetries such as those observed in the cortex and epithalamus are directional. This means that molecular and anatomical features located on one side of a given structure are observed in most individuals. For instance, in humans, the neuronal tract connecting the language areas is enlarged in the left hemisphere. When asymmetries are fixed, their molecular mechanisms can be studied using mutants displaying different phenotypes: left or right isomerism of the structure, reversed asymmetry or random asymmetry. Our understanding of asymmetry in the nervous system has been widely enriched thanks to the characterization of mutants affecting epithalamus asymmetry. Furthermore, two decades ago, pioneering studies revealed that a specific morphogen, Nodal, active only on one side of the embryo during development is an important molecule in asymmetry patterning. In this review, I have gathered important data bringing insight into the origin and evolution of epithalamus asymmetry and the role of Nodal in metazoans. After a short introduction on brain asymmetries (chapter I), I secondly focus on the molecular and anatomical characteristics of the epithalamus in vertebrates and explore some functional aspects such as its photosensitive ability related to the pineal complex (chapter II). Third, I discuss homology relationship of the parapineal organ among vertebrates (chapter III). Fourth, I discuss the possible origin of the epithalamus, presenting cells displaying photosensitive properties and/or asymmetry in the anterior part of the body in non-vertebrates (chapter IV). Finally, I report Nodal signaling expression data and functional experiments performed in different metazoan groups (chapter V).
Type de document :
Article dans une revue
Mechanisms of Development, Elsevier, 2017, 〈10.1016/j.mod.2017.09.002〉
Liste complète des métadonnées

Littérature citée [141 références]  Voir  Masquer  Télécharger

http://hal.upmc.fr/hal-01613167
Contributeur : Gestionnaire Hal-Upmc <>
Soumis le : lundi 9 octobre 2017 - 13:42:12
Dernière modification le : mercredi 11 octobre 2017 - 01:19:41

Fichier

 Accès restreint
Fichier visible le : 2018-04-03

Connectez-vous pour demander l'accès au fichier

Identifiants

Collections

Citation

Agnès Boutet. The evolution of asymmetric photosensitive structures in metazoans and the Nodal connection. Mechanisms of Development, Elsevier, 2017, 〈10.1016/j.mod.2017.09.002〉. 〈hal-01613167〉

Partager

Métriques

Consultations de la notice

7