Research in Drosophila melanogaster has shown that loss of Lola-N, a splice variant of the Lola transcription factor expressed in differentiated neurons, results in brain tumour formation. Lola-N represses the expression of stem cell-associated genes and its loss results in dedifferentiation of neurons, derepression of neural stem cell genes and proliferation. Thus, fully differentiated neurons are capable of tumour formation in fruit flies if an essential mediator of stem cell gene repression is lost.