Differential expression of components of the retinoic acid signaling pathway in the adult mouse olfactory epithelium

Position within a tissue often correlates with cellular phenotype, for example, differential expression of odorant receptors and cell adhesion molecules across the olfactory mucosa (OM). The association between position and phenotype is often paralleled by gradations in the concentration of retinoic acid (RA), caused by differential expression of the RA synthetic enzymes, the retinaldehyde dehydrogenases (RALDH). We show here that RALDH-1, -2, and -3 are enriched in the sustentacular cells, deep fibroblasts of the lamina propria, and the superficial fibroblasts, respectively, of the ventral and lateral OM as compared to the dorsomedial OM. The shift from high to low expression of the RALDHs matches the boundary defined by the differential expression of OCAM/mamFasII. Further, we found that RA-binding proteins are expressed in the epithelium overlying the RALDH-3 expressing fibroblasts of the lamina propria. Both findings suggest that local alterations in RA concentration may be more important than a gradient of RA across the epithelial plane, per se. In addition, RALDH-3 is found in a small population of basal cells in the ventral and lateral epithelium, which expand and contribute to the neuronal lineage following MeBr lesion. Indeed, transduction with a retrovirus expressing a dominant negative form of retinoic acid receptor type alpha blocks the reappearance of mature, olfactory marker protein (OMP) (+) olfactory neurons as compared to empty vector. These results support the notion of a potential role for RA, both in maintaining the spatial organization of the normal olfactory epithelium and in reestablishing the neuronal population during regeneration after injury

Ascl1 (Mash1) knockout perturbs differentiation of nonneuronal cells in olfactory epithelium

The embryonic olfactory epithelium (OE) generates only a very few olfactory sensory neurons when the basic helix-loop-helix transcription factor, ASCL1 (previously known as MASH1) is eliminated by gene mutation. We have closely examined the structure and composition of the OE of knockout mice and found that the absence of neurons dramatically affects the differentiation of multiple other epithelial cell types as well. The most prominent effect is observed within the two known populations of stem and progenitor cells of the epithelium. The emergence of horizontal basal cells, a multipotent progenitor population in the adult epithelium, is anomalous in the Ascl1 knockout mice. The differentiation of globose basal cells, another multipotent progenitor population in the adult OE, is also aberrant. All of the persisting globose basal cells are marked by SOX2 expression, suggesting a prominent role for SOX2 in progenitors upstream of Ascl1. However, NOTCH1-expressing basal cells are absent from the knockout; since NOTCH1 signaling normally acts to suppress Ascl1 via HES1 and drives sustentacular (Sus) cell differentiation during adult epithelial regeneration, its absence suggests reciprocity between neurogenesis and the differentiation of Sus cells. Indeed, the Sus cells of the mutant mice express a markedly lower level of HES1, strengthening that notion of reciprocity. Duct/gland development appears normal. Finally, the expression of cKIT by basal cells is also undetectable, except in those small patches where neurogenesis escapes the effects of Ascl1 knockout and neurons are born. Thus, persistent neurogenic failure distorts the differentiation of multiple other cell types in the olfactory epithelium

The complete chloroplast genome of a new candidate cultivar, Dae Ryun, of Abeliophyllum distichum Nakai (Oleaceae)

To understand genetic features of new candidate cultivar, Dae Ryun of A. distichum, chloroplast genome was sequenced. Its length is 156,019 bp and has four subregions: 86,783 bp of large single-copy (LSC) and 17,828 bp of small single-copy (SSC) regions are separated by 25,704 bp of inverted repeat (IR) regions including 133 genes (87 protein-coding genes, 8 rRNAs, and 37 tRNAs). Overall GC content is 35.8%. Intraspecies sequence variations among four A. distichum chloroplast genomes present various numbers. Phylogenetic trees show that A. distichum is clustered with 12 Forsythia species

The labeling intensity of Hes1 is reduced in Ascl1 knockout compared to heterozygote.

<p>Multiple sections from various ages were stained for Hes1 and imaged. The intensity of nuclear labeling was sampled from 50 consecutive nuclei and pixel intensity for 50 single-pixel intensity readings were measured for Hes1(+) consecutive nuclei in the olfactory domain and the respiratory domain using ImageJ (in other words, unstained cells were not measured). A ratio of intensity values was calculated for olfactory epithelium to respiratory epithelium for each genotype at each embryonic time point described. At all time points examined the calculated OE/RE intensity ratio is less for <b>Ascl1 knockout</b><b>mice</b> than <b>heterozygotes</b>.</p