Profiling data on the developing olfactory/GnRH system reveal cellular and molecular pathways potentially relevant for the Kallmann syndrome.

ABSTRACT: The olfactory sensory system is formed by the coordinated morphogenesis and differentiation of the peripheral olfactory epithelium (OE) and the anterior forebrain. At early stages, immature olfactory receptor neurons (ORN) elongate their axons to penetrate the brain basement membrane, contact and form synapses with projection neurons of the olfactory bulb primordium. Axonal elongation is accompanied by migration of the GnRH+ neurons, followed by their ingression in the septo-hypothalamic area of the forebrain. This process is specifically impaired in the KallmannM-bM-^@M-^Ys syndrome (KS), a disorder characterized by anosmia and central hypogonadism. A set of transcription factors are master regulators of olfactory connectivity and GnRH neuron migration. We explored the transcriptional network underlying this process, by profiling the OE and adjacent mesenchyme at distinct embryonic ages. We also profiled the OE from embryos null for Dlx5, a homeogene essential for olfactory development, that causes a KS-like phenotype when deleted. We also applied analysis of conserved co-expression to integrate the obtained data with information on KS disease genes. The prevalent categories of genes differentially expressed during development are neuronal differentiation, extracellular remodelling and cell adhesion. From the analysis of Dlx5 mutant tissues we identify about 120 genes with a prevalence of intermediate filaments, cell signalling, epithelial and neuronal differentiation. Filtering for true OE expression and for the presence of Dlx5 binding sites, yielded twenty genes, of the following categories: 1) transmembrane adhesion/receptor molecules, 2) axon-glia interaction molecules, 3) synaptic proteins, 4) scaffold/adapter for signalling molecules. To functionally analyze these genes in vivo, we used three zebrafish fluorescent reporter zebrafish strains, in which we monitored early phases of olfactory/GnRH development upon gene downmodulation. The depletion of three (of five) Dlx5 targets affected axonal extension and targeting, while two (of two) altered GnRH neuron position and neurite organization. In one experiment we compare the olfactrory sensory epithelium from wild-type embryos, at three times of development, i.e. E11.5, E12.5 and E14.5. In a second experiment we compare the olfactory sensory epithelium from wild-type embryo with that from Dlx5 knock-out embryos, at the age E12.5

ORGANISM(S): Mus musculus

SUBMITTER: Paolo Provero 

PROVIDER: E-GEOD-52800 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress