Expression of segment polarity genes in brachiopods supports a non-segmental ancestral role of engrailed for bilaterians

The diverse and complex developmental mechanisms of segmentation have been more thoroughly studied in arthropods, vertebrates and annelids distantly related animals considered to be segmented. Far less is known about the role of segmentation genes in organisms that lack a segmented body. Here we inv...

Full description

Saved in:
Bibliographic Details
Published inbioRxiv
Main Authors Vellutini, Bruno Cossermelli, Hejnol, Andreas
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 12.08.2016
Subjects
Embryogenesis
Invertebrates
Pattern formation
pax2 protein
Pax6 protein
Phylogeny
Polarity
Segmentation
Online AccessGet full text

Cover

More Information
Summary:The diverse and complex developmental mechanisms of segmentation have been more thoroughly studied in arthropods, vertebrates and annelids distantly related animals considered to be segmented. Far less is known about the role of segmentation genes in organisms that lack a segmented body. Here we investigate the expression of the arthropod segment polarity genes engrailed, wnt1 and hedgehog in the development of brachiopods marine invertebrates without a subdivided trunk but closely related to the segmented annelids. We found that a stripe of engrailed expression demarcates the ectodermal boundary that delimits the anterior region of Terebratalia transversa and Novocrania anomala embryos. In T. transversa, this engrailed domain is abutted by a stripe of wnt1 expression in a pattern similar to the parasegment boundaries of insects except for the expression of hedgehog, which is restricted to endodermal tissues of the brachiopod embryos. We found that pax6 and pax2/5/8, putative regulators of engrailed, also demarcate the anterior boundary in the two species, indicating these genes might be involved in the anterior patterning of brachiopod larvae. In a comparative phylogenetic context, these findings suggest that bilaterians might share an ancestral, non-segmental domain of engrailed expression during early embryogenesis.
DOI:10.1101/029892