The zebrafish has recently become a source of new data on the mechanisms of neural stem cell (NSC) maintenance and ongoing neurogenesis in adult brains. In this vertebrate, neurogenesis occurs at high levels in all ventricular regions of the brain, and brain injuries recover successfully, owing to the recruitment of radial glia, which function as NSCs. This new vertebrate model of adult neurogenesis is thus advancing our knowledge of the molecular cues in use for the activation of NSCs and fate of their progeny. Because the regenerative potential of somatic stem cells generally weakens with increasing age, it is important to assess the extent to which zebrafish NSC potential decreases or remains unaltered with age. We found that neurogenesis in the ventricular zone, in the olfactory bulb, and in a newly identified parenchymal zone of the telencephalon indeed declines as the fish ages and that oligodendrogenesis also declines. In the ventricular zone, the radial glial cell population remains largely unaltered morphologically but enters less frequently into the cell cycle and hence produces fewer neuroblasts. The neuroblasts themselves do not change their behavior with age and produce the same number of postmitotic neurons. Thus, decreased neurogenesis in the physiologically aging zebrafish brain is correlated with an increasing quiescence of radial glia. After injuries, radial glia in aged brains are reactivated, and the percentage of cell cycle entry is increased in the radial glia population. However, this reaction is far less pronounced than in younger animals, pointing to irreversible changes in aging zebrafish radial glia.

The strawberry fruit proteins Fra a 1.01E-1.08 are homologues of the major birch pollen allergen Bet v 1. Three of the proteins are known to have essential biological functions in pigment formation during fruit ripening and seem to be responsible for allergic reactions to strawberry fruit. We evaluated the cross-reactive allergenic potential of these putative strawberry allergens in patients allergic to birch pollen. Activation of basophils of eight atopic patients was studied using different concentrations of Fra a 1 isoforms. Bet v 1a was used as control and as atopic patient selection criterion. Although Fra a 1.01E-1.08 have amino acid sequence identities of 74.5-97.5% with Fra a 1.02, the basophil activation mediated by the eight Fra a 1 proteins differed substantially. Fra a 1.03 and Fra a 1.02 showed the highest activation of basophils, 73 and 66% of total basophils, respectively. On the basis of the high relative expression of the gene Fra a 1.02 in ripe strawberry fruits of allergenic varieties, Fra a 1.02 was identified as the main strawberry allergen of the Bet v 1 superfamily. Knowledge of the allergenic potential of Fra a 1.02/1.03 will help to improve food safety and can serve as a valuable marker for the development of red-fruited hypoallergenic strawberry cultivars.

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BACKGROUND: Allergy to food is a hypersensitivity disorder of the immune system to normally harmless food ingredients. A promising solution for allergenic patients is the development of hypoallergenic food. OBJECTIVE: Selection and breeding of low-allergenic variety is the conventional strategy to produce hypoallergenic food. The strawberry fruit proteins Fra a 1.01E, Fra a 1.02 and Fra a 1.03 are homologous of the major birch pollen allergen Bet v1 but their individual allergenic potentials are unknown. METHOD: We produced the recombinant Fra a allergens and evaluated their cross allergenic potential in birch pollen allergic patients by a basophil activation test. Anti-Fra a 1.02 antibodies were also used to screen for allergen deficient strawberry lines. RESULTS: Although Fra a 1.01E, Fra a 1.02 and Fra a 1.03 have sequence similarities of 70, 71 and 74% with Bet v 1 Fra a 1.02 showed the highest allergenic potential. The data support the role of Fra a 1.02 as the major allergen for individuals affected by a strawberry allergy. The screening of strawberry varieties detected genotypes with significantly reduced levels of the allergen. CONCLUSION: Genotypes with reduced Fra a 1.02 proteins might serve as starting material for the breeding of hypoallergenic strawberry varieties.

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