Sensory organ formation in Drosophila is activated by proneural genes that encode basic-helix-loop-helix (bHLH) transcription factors. These genes are antagonized by hairy and other proline-bHLH proteins, hairy has not been shown to bind to DNA and has been proposed to form inactive heterodimers with proneural activator proteins. Here, we show that hairy does bind to DNA and has novel DNA-binding activity: hairy prefers a noncanonical site, CACGCG, although it also binds to related sites. Mutation of a single CACGCG site in the achaete [ac) proneural gene blocks hairy-mediated repression of ac transcription in cultured Drosopbila cells. Moreover, the same CACGCG mutation in an ac minigene transformed into Drosopbila creates ectopic sensory hair organs like those seen in bairy mutants. Together these results indicate that hairy represses sensory organ formation by directly repressing transcription of the ac proneural gene.

The formation of the vertebrate optic cup is a morphogenetic event initiated after the optic vesicle contacts the overlying surface/pre-lens ectoderm. Placodes form in both the optic neuroepithelium and lens ectoderm. Subsequently, both placodes invaginate to form the definitive optic cup and lens, respectively. We examined the role of the lens tissue in inducing and/or maintaining optic cup invagination in ovo. Lens tissue was surgically removed at various stages of development, from pre-lens ectoderm stages to invaginating lens placode. Removal of the pre-lens ectoderm resulted in persistent optic vesicles that initiated neural retinal differentiation but failed to invaginate. In striking contrast, ablation of the lens placode gave rise to optic vesicles that underwent invagination and formed the optic cup. The results suggest that: (1) the optic vesicle neuroepithelium requires a temporally specific association with pre-lens ectoderm in order to undergo optic cup morphogenesis; and (2) the optic cup can form in the absence of lens formation. If ectopic BMP is added, a neural retina does not develop and optic cup morphogenesis fails, although lens formation appears normal. FGF-induced neural retina differentiation in the absence of the pre-lens ectoderm is not sufficient to create an optic cup. We hypothesize the presence of a signal coming from the pre-lens ectoderm that induces the optic vesicle to form an optic cup.

Diffuse intrinsic pontine gliomas arise almost exclusively in children, and despite advances in treatment, the majority of patients die within 2 years after initial diagnosis. Because of their infiltrative nature and anatomic location in an eloquent area of the brain, most pontine gliomas are treated without a surgical biopsy. The corresponding lack of tissue samples has resulted in a limited understanding of the underlying genetic and molecular biologic abnormalities associated with pontine gliomas, and is a substantial obstacle for the preclinical testing of targeted therapeutic agents for these tumors. We have established a human glioma cell line that originated from surgical biopsy performed on a patient with a pontine glioma. To insure sustainable in vitro propagation, tumor cells were modified with hTERT (human telomerase ribonucleoprotein reverse transcriptase), and with a luciferase reporter to enable non-invasive bioluminescence imaging. The hTERT modified cells are tumorigenic in athymic rodents, and produce brainstem tumors that recapitulate the infiltrative growth of brainstem gliomas in patients.

Gliomas synaptically integrate into neural circuits1,2. Previous research has demonstrated bidirectional interactions between neurons and glioma cells, with neuronal activity driving glioma growth1–4 and gliomas increasing neuronal excitability2,5–8. Here we sought to determine how glioma-induced neuronal changes influence neural circuits underlying cognition and whether these interactions influence patient survival. Using intracranial brain recordings during lexical retrieval language tasks in awake humans together with site-specific tumour tissue biopsies and cell biology experiments, we find that gliomas remodel functional neural circuitry such that task-relevant neural responses activate tumour-infiltrated cortex well beyond the cortical regions that are normally recruited in the healthy brain. Site-directed biopsies from regions within the tumour that exhibit high functional connectivity between the tumour and the rest of the brain are enriched for a glioblastoma subpopulation that exhibits a distinct synaptogenic and neuronotrophic phenotype. Tumour cells from functionally connected regions secrete the synaptogenic factor thrombospondin-1, which contributes to the differential neuron–glioma interactions observed in functionally connected tumour regions compared with tumour regions with less functional connectivity. Pharmacological inhibition of thrombospondin-1 using the FDA-approved drug gabapentin decreases glioblastoma proliferation. The degree of functional connectivity between glioblastoma and the normal brain negatively affects both patient survival and performance in language tasks. These data demonstrate that high-grade gliomas functionally remodel neural circuits in the human brain, which both promotes tumour progression and impairs cognition.