Wnt/β-catenin signalling is necessary for gut differentiation in a marine annelid, Platynereis dumerilii

Abstract

BackgroundWnt/β-catenin (or canonical) signalling pathway activity is necessary and used independently several times for specification of vegetal fate and endoderm, gut differentiation, maintenance of epithelium in adult intestine and the development of gut-derived organs in various vertebrate and non-vertebrate organisms. However, its conservation in later stages of digestive tract development still remains questionable due to the lack of detailed data, mainly from Spiralia.ResultsHere we characterize the Pdu-Tcf gene, a Tcf/LEF orthologue and a component of Wnt/β-catenin pathway from Platynereis dumerilii, a spiralian, marine annelid worm. Pdu-Tcf undergoes extensive alternative splicing in the C-terminal region of the gene generating as many as eight mRNA isoforms some of which differ in the presence or absence of a C-clamp domain which suggests a distinct DNA binding activity of individual protein variants. Pdu-Tcf is broadly expressed throughout development which is indicative of many functions. One of the most prominent domains that exhibits rather strong Pdu-Tcf expression is in the putative precursors of endodermal gut cells which are detected after 72 h post-fertilization (hpf). At day 5 post-fertilization (dpf), Pdu-Tcf is expressed in the hindgut and pharynx (foregut), whereas at 7 dpf stage, it is strongly transcribed in the now-cellularized midgut for the first time. In order to gain insight into the role of Wnt/β-catenin signalling, we disrupted its activity using pharmacological inhibitors between day 5 and 7 of development. The inhibition of Wnt/β-catenin signalling led to the loss of midgut marker genes Subtilisin-1, Subtilisin-2, α-Amylase and Otx along with a drop in β-catenin protein levels, Axin expression in the gut and nearly the complete loss of proliferative activity throughout the body of larva. At the same time, a hindgut marker gene Legumain was expanded to the midgut compartment under the same conditions.ConclusionsOur findings suggest that high Wnt/β-catenin signalling in the midgut might be necessary for proper differentiation of the endoderm to an epithelium capable of secreting digestive enzymes. Together, our data provide evidence for the role of Wnt/β-catenin signalling in gut differentiation in Platynereis.

Dynamic Changes in the Global Transcriptome and MicroRNAome Reveal Complex miRNA-mRNA Regulation in Early Stages of the Bi-Directional Development of Echinococcus granulosus Protoscoleces

“…A recent study proposed that MAPK may be a therapeutic target in E. granulosus through the suppression of MKK3/6 and MEK1/2 (Zhang et al, 2019). Furthermore, some Wnt-pathway related proteins, such as the frizzled receptor eg-fz4, have been shown to be highly expressed in PSC cultured in vitro toward adult maturation, and that they may be involved in early development of the nervous system and gut-derived organs (Pan et al, 2006;Dezaki et al, 2016;Zidek et al, 2018). These results are consistent with a previous study (Macchiaroli et al, 2017), and suggest that the down-regulation of miR-71 in SSD might trigger the MAPK and Wnt pathways in growth and development.…”

FoxA expression pattern in two polychaete species, Alitta virens and Platynereis dumerilii: Examination of the conserved key regulator of the gut development from cleavage through larval life, postlarval growth, and regeneration

“…The information on molecular markers of the endoderm in lophotrochozoans is also limited. Speaking of transcription factors in nereids, specific intestinal expression has been described only in the early metatrochophore for the orthologs of xlox , cad (Kulakova et al, ), hnf4 (Achim et al, ), and tcf (Žídek et al, ). Thus, foxA is the earliest known regulatory gene with endodermal activity in errant annelids.…”

“…foxA activation in the posterior midgut during regeneration is followed by the ectodermal expression in the hindgut primordium along with its morphogenesis, just as it does in the course of normal development. This reiterative dynamic suggests that foxA may be involved in its coordination, perhaps alongside with the Wnt signaling, which is active at the posterior body end in A. virens and P. dumerilii (Janssen et al, , Žídek et al, ; Kozin et al, ).…”

Desmosomal connectomics of all somatic muscles in an annelid larva

“…To study the organisation of a body-wide tensile network and its motor control, here we reconstruct the desmosomal connectome of larval Platynereis dumerilii from serial electron microscopy images of an entire larva (Randel et al, 2015). P. dumerilii or 'the nereid' is a marine annelid worm that has been used as a laboratory animal (Fischer and Dorresteijn, 2004;Kuehn et al, 2019) to study developmental patterning (Gazave et al, 2017;Handberg-Thorsager et al, 2018;Özpolat et al, 2017;Schneider and Bowerman, 2007;Vopalensky et al, 2019;Žídek et al, 2018), the lunar control of reproduction (Poehn et al, n.d.;Zantke et al, 2014;Zurl et al, 2021), hormonal signalling (Schenk et al, 2016), photobiology (Ayers et al, 2018;Gühmann et al, 2015), neuromodulation (Williams et al, 2017), neuronal cell types (Vergara et al, 2017) and neuronal circuits (Bezares-Calderón et al, 2018;Randel et al, 2014). In Platynereis, muscle development starts in the early non-feeding larval stages (Fischer et al, 2010).…”