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Dev Biol. April 15, 2006; 292 (2): 470-85.

Mxi1 is essential for neurogenesis in Xenopus and acts by bridging the pan-neural and proneural genes.

Klisch TJ , Souopgui J , Juergens K , Rust B , Pieler T , Henningfeld KA .

We have isolated and characterized Xenopus Mxi1, a member of the Myc/Max/Mad family of bHLHZip transcription factors. Xmxi1 transcripts are present during gastrulation and early neurula stages, earlier and in broader domains as compared to the neuronal determination factor neurogenin (X-ngnr-1). Consistent with an early role in neurogenesis, Xmxi1 is positively regulated by Sox3, SoxD, and proneural genes, as well as negatively by the Notch pathway. Loss-of-function experiments demonstrate an essential role for Xmxi1 in the establishment of a mature neural state that can be activated by factors that induce neuronal differentiation, such as SoxD and X-ngnr-1. Overexpression of Xmxi1 in Xenopus embryos results in ectopic activation of Sox3, an early pan-neural marker of proliferating neural precursor cells. Within the neural plate, the neuronal differentiation marker N-tubulin and cell cycle control genes such as XPak3 and p27(Xic1) are inhibited, but the expression of early determination and differentiation markers, including X-ngnr-1 and X-MyT1, is not affected. Inhibition of neuronal differentiation by Xmxi1 is only transient, and, at early tailbud stages, both endogenous and ectopic neurogenesis are observed. While Xmxi1 enhances cell proliferation and apoptosis in the early Xenopus embryo, both activities appear not to be required for the function of Xmxi1 in primary neurogenesis.

PubMed ID: 16457797
Article link: Dev Biol.

Genes referenced: bcl2 cdknx elavl1 gal.2 hist1h4d mxi1 myc myt1 neurod1 neurog1 neurog2 nog notch1 odc1 pak3 smad1 sox15 sox3 tubb2b

Morpholinos referenced: mxi1 MO1 mxi1 MO2 neurog2 MO2

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