From genotype to olfactory neuron phenotype: the role of the Olf-1-binding site

Cloning of an olfactory sensory neuron-specific protein in the land snail (Eobania vermiculata)

We have isolated a gene encoding for an olfactory sensory neuron (OSN)-specific protein in an invertebrate, the land snail Eobania vermiculata (GenBank accession number AY147909). Using in situ hybridization, we detected expression of its mRNA in the dendrite, cell body and axon of OSNs. By neural tracing, using the lipophilic tracer DiI and in situ hybridization, we have revealed the organization of OSNs and their connections with olfactory glomeruli in the land snail. Sequence and expression pattern analogy of land snail protein with olfactory marker protein (OMP) from vertebrates suggest that the land snail protein is an OMP-like protein. This protein could represent a plesiomorphic character in the evolution of olfactory proteins.

Early B-cell factor (O/E-1) is a promoter of adipogenesis and involved in control of genes important for terminal adipocyte differentiation

Olf-1/early B-cell factor (O/E-1) is a transcription factor important for B-lymphocyte and neuronal gene regulation. Here we report that all three known O/E genes (O/E-1, -2, and -3) are expressed in mouse adipose tissue and are upregulated during adipocyte differentiation. Forced expression of O/E-1 in either the preadipocyte cell line 3T3-L1 or mouse embryonic fibroblasts augmented adipogenesis, and constitutive expression of O/E-1 in uncommitted NIH 3T3 fibroblasts led to initiation of adipocyte differentiation. Furthermore, a dominant negative form of O/E-1 partially suppressed 3T3-L1 adipogenesis, indicating that expression from endogenous O/E target genes is required for 3T3-L1 terminal differentiation. Thus, our data point to the importance of O/E target genes for adipocyte differentiation and suggest a novel role for O/E-1 as an initiator and stimulator of adipogenesis.

LacZ and OMP are co-expressed during ontogeny and regeneration in olfactory receptor neurons of OMP promoter-lacZ transgenic mice

The ontogeny and cellular specificity of expression of beta-galactosidase activity and olfactory marker protein (OMP) are compared in olfactory tissue of the H-OMP-lacZ-3 line of transgenic mice. In this line the expression of lacZ is driven by a 0.3 kb fragment of the rat OMP promoter. During fetal development, lacZ expression is detectable in olfactory receptor neurons (ORNs) shortly after the initial appearance of endogenous OMP. The beta-galactosidase marker was observed only in mature olfactory receptor neurons where it co-localized with endogenous OMP. It was absent from immature neurons that express the growth associated phosphoprotein B50/GAP43. Lesion of the peripheral olfactory pathway by intranasal irrigation with Triton X-100 eliminated expression of both OMP and lacZ in the olfactory neuroepithelium. Subsequent regeneration of the full complement of olfactory receptor neurons was associated with co-expression of both OMP and beta-galactosidase activity. Neither OMP nor beta-galactosidase activity was induced in any other cell type of the regenerating olfactory mucosa. Thus, as little as 0.3 kb of the OMP promoter has the ability to target lacZ expression to olfactory receptor neurons in a temporally and spatially defined manner. We discuss the potential utility of this transgenic line for future studies of the olfactory system.