Comparative analysis of Wnt expression identifies a highly conserved developmental transition in flatworms

BMC Biology

Research Article

Francesca Jarero¹  Peter D. Olson¹  Uriel Koziol²  Klaus Brehm³ 

[1] Department of Life Sciences, The Natural History Museum, London, UK;Sección Bioquímica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay;University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany;University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany;

关键词: Antero-posterior axis;    Cestodes;    FoxQ2;    Metamorphosis;    Myocyte;    Phylotypic;    Planarian;    Platyhelminthes;    SFRP;    Six3/6;    Wnt;   

DOI  :  10.1186/s12915-016-0233-x

 received in 2015-12-29, accepted in 2016-01-25,  发布年份 2016

来源: Springer

【 摘 要 】

BackgroundEarly developmental patterns of flatworms are extremely diverse and difficult to compare between distant groups. In parasitic flatworms, such as tapeworms, this is confounded by highly derived life cycles involving indirect development, and even the true orientation of the tapeworm antero-posterior (AP) axis has been a matter of controversy. In planarians, and metazoans generally, the AP axis is specified by the canonical Wnt pathway, and we hypothesized that it could also underpin axial formation during larval metamorphosis in tapeworms.ResultsBy comparative gene expression analysis of Wnt components and conserved AP markers in the tapeworms Echinococcus multilocularis and Hymenolepis microstoma, we found remarkable similarities between the early stages of larval metamorphosis in tapeworms and late embryonic and adult development in planarians. We demonstrate posterior expression of specific Wnt factors during larval metamorphosis and show that scolex formation is preceded by localized expression of Wnt inhibitors. In the highly derived larval form of E. multilocularis, which proliferates asexually within the mammalian host, we found ubiquitous expression of posterior Wnt factors combined with localized expression of Wnt inhibitors that correlates with the asexual budding of scoleces. As in planarians, muscle cells are shown to be a source of secreted Wnt ligands, providing an explanation for the retention of a muscle layer in the immotile E. multilocularis larva.ConclusionsThe strong conservation of gene expression between larval metamorphosis in tapeworms and late embryonic development in planarians suggests, for the first time, a homologous developmental period across this diverse phylum. We postulate these to represent the phylotypic stages of these flatworm groups. Our results support the classical notion that the scolex is the true anterior end of tapeworms. Furthermore, the up-regulation of Wnt inhibitors during the specification of multiple anterior poles suggests a mechanism for the unique asexual reproduction of E. multilocularis larvae.

【 授权许可】

CC BY   
© Koziol et al. 2016