tokens: CONCLUSIONS : XCoe2 may play a pivotal role in the transcriptional cascade that specifies primary neurons in Xenopus embryos : by maintaining Delta - Notch signalling , XCoe2 stabilises the higher neural potential of selected progenitor cells that express X - ngnr - 1 , ensuring the transition between neural competence and irreversible commitment to a neural fate ; and it promotes neuronal differentiation by activating XNeuroD expression , directly or indirectly .