A hindbrain-repressive Wnt3a/Meis3/Tsh1 circuit promotes neuronal differentiation and coordinates tissue maturation

Abstract

The HA tag fragment was cut (ClaI/EcoRI) from a pcDNA3 plasmid (ClaI/EcoRI). A Meis3 full-length fragment was cut (EcoRI/NotI) from pCS107 and subcloned into pGEM T-Easy. The HA tag was subcloned into pGEM-T Easy-Meis3 (ClaI/EcoRI). The HA-Meis3 was then cut (ClaI/NotI) and subcloned back into the pCS107 vector. Meis3 5ЈUTR probe plasmidA fragment of the Meis3 5ЈUTR was PCR amplified by Meis3UTR primers (supplementary material Table S1), from a pGL3 plasmid containing Meis3 5Ј genomic sequence, the entire 5ЈUTR, the 1st exon and part of the 1st intron (Elkouby et al., 2010). The Meis3 5ЈUTR fragment was cloned into pGEM-T Easy. SUMMARYDuring development, early inducing programs must later be counterbalanced for coordinated tissue maturation. In Xenopus laevis embryos, activation of the Meis3 transcription factor by a mesodermal Wnt3a signal lies at the core of the hindbrain developmental program. We now identify a hindbrain restricting circuit, surprisingly comprising the hindbrain inducers Wnt3a and Meis3, and Tsh1 protein. Functional and biochemical analyses show that upon Tsh1 induction by strong Wnt3a/Meis3 feedback loop activity, the Meis3-Tsh1 transcription complex represses the Meis3 promoter, allowing cell cycle exit and neuron differentiation. Meis3 protein exhibits a conserved dual-role in hindbrain development, both inducing neural progenitors and maintaining their proliferative state. In this regulatory circuit, the Tsh1 co-repressor controls transcription factor gene expression that modulates cell cycle exit, morphogenesis and differentiation, thus coordinating neural tissue maturation. This newly identified Wnt/Meis/Tsh circuit could play an important role in diverse developmental and disease processes.

Meis2 is a Pax6 co-factor in neurogenesis and dopaminergic periglomerular fate specification in the adult olfactory bulb

“…In the hindbrain, the PBC proteins Pbx1-4 and members of the Hox clusters are major Meis-binding partners (Elkouby et al, 2012;Maeda et al, 2002;Vlachakis et al, 2001;Wassef et al, 2008), but only a few proteins are known to associate with Meis family proteins in the mes-, di-or telencephalon. These include Oct1 (Slc22a1), which cooperates with the Meis-related Prep1 (Pknox1) to control expression of gonadotropin-releasing hormone in the hypothalamus, and Otx2, Pax3 and Pax7 during tectal development (Agoston and Schulte, 2009;Agoston et al, 2012;Rave-Harel et al, 2004).…”

Spalt-like 4 promotes posterior neural fates via repression of pou5f3 family members in Xenopus

“…The homeobox gene gbx2 is a direct target of canonical Wnt signaling and primarily serves to localize the isthmus and induce neural crest (Simeone, 2000;Li et al, 2009). The meis3 gene, which is required for hindbrain and neuronal differentiation, is directly activated by Wnt3a from the dorsal lateral marginal zone (Elkouby et al, 2010(Elkouby et al, , 2012. The caudal homologs Cdx1 and Cdx4 are direct Wnt targets in the mouse (Prinos et al, 2001;Pilon et al, 2006Pilon et al, , 2007 and have overlapping roles in posterior development of the three germ layers (Isaacs et al, 1998;Faas and Isaacs, 2009;van de Ven et al, 2011).…”

A novel role for Pax6 in the segmental organization of the hindbrain

“…Vhnf1 upregulates Kreisler, which in turn induces Krox20 and Hoxb3 in r5 and Hoxa3 in r5/r6 Manzanares et al, 1999). Other TFs, such as Pbx/Meis, are also essential for hindbrain patterning via their synergistic activities with Hox factors (Aamar and Frank, 2004;Elkouby et al, 2012;Vlachakis et al, 2001;Wassef et al, 2008). Additional factors also modulate the expression of these TFs, such as Nab and Nlz (also known as Neurl1a), which colocalize with Krox20 but repress its transcription, leading to Krox20 restriction to the correct rhombomeres (García-Gutiérrez et al, 2011;Mechta-Grigoriou et al, 2000;Runko and Sagerström, 2003).…”