Biomedical subjects

Esther Alcorta

Publications and source records attributed to Esther Alcorta.

5 recordsLinked to original sources

PubMed2006

The Inositol 1,4,5-triphosphate kinase1 gene affects olfactory reception in Drosophila melanogaster.

The Inositol 1,4,5-triphosphate (IP3) route is one of the two main transduction cascades that mediate olfactory reception in Drosophila melanogaster. The activity of IP3 kinase1 reduces the levels of this substrate by phosphorylation into inositol 1,3,4,5-tetrakiphosphate (IP4). We show here that the gene is expressed in olfactory sensory organs as well as in the rest of the head. To evaluate in vivo the olfactory functional effects of up-regulating IP3K1, individuals with directed genetic changes at the reception level only were generated using the UAS/Gal4 method. In this report, we described the consequences in olfactory perception of overexpressing the IP3Kinase1 gene at eight different olfactory receptor-neuron subsets. Six out of the eight studied Gal-4/UAS-IP3K1 hybrids displayed abnormal behavioral responses to ethyl acetate, acetone, ethanol or propionaldehyde. Specific behavioral defects corresponded to the particular neuronal olfactory profile. These data confirm the role of the IP3kinase1 gene, and consequently the IP3 transduction cascade, in mediating olfactory information at the reception level.

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PubMed2004

Altered endogenous activation of CREB in the suprachiasmatic nucleus of mice with retinal degeneration.

The effect of cone- and rod-cell loss on the activation of transcription factor CREB (by phosphorylation at Ser133) was examined in the pacemaker of mammals, the suprachiasmatic nucleus (SCN). For this purpose, brain sections of rd/rd and wild-type C3H mice were immunolabeled with a polyclonal antibody that recognises p-CREB, i.e., the activated form of the protein. Both rd/rd and wild-type mice maintained in constant darkness showed a circadian variation of p-CREB nuclear staining: the number of immunopositive nuclear pixels at the subjective night was higher than the one observed at the subjective day. However, some differences were detected between both groups: (1) p-CREB immunolabelling in the SCN of rd/rd mice was significantly reduced throughout the 24-h cycle; (2) the time in which the activation of CREB begins to increase at the subjective night in these mice is delayed with regard to wild-type mice. When a light stimulus was given at the subjective night p-CREB immunostaining significantly increased in the SCN of both rd/rd and wild-type mice when compared to basal levels, while no significant effect was found when the stimulus was given at the subjective day. Taken together, our results suggest that despite lower levels of p-CREB, indicating that something is altered in the SCN of rd/rd mice, the main mechanisms of the clock (e.g., circadian oscillation, readjustment by light) are still fully functional in these mice. The present study supports the idea that the CREB/CRE pathway is a component of the circadian clock molecular mechanism.

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PubMed2004

The cAMP transduction cascade mediates olfactory reception in Drosophila melanogaster.

Two main second messenger systems depending on IP3 and cAMP have been related to olfaction in vertebrates as well as invertebrates. In Drosophila melanogaster, the availability of mutations affecting one or the other pathway (rdgB and norpA or rut and dnc, respectively) allowed showing of abnormal olfactory behavior phenotypes associated with olfactory transduction in complete living animals. However, because rut and dnc genes showed ubiquitous expression at olfactory receptor organs and some brain locations, the mutant behavior cannot be assigned exclusively to olfactory reception. In this report, overexpression of the dnc gene directed specifically to different olfactory receptor neuron subsets was used to produce dominant mutants. Abnormal olfactory behavior was found in 62.5% of the 8 lines studied in response to some odorants, depending on the affected neuronal subset. These results suggest that even for a small number of tested odorants (5), cAMP cascade is involved in olfactory reception to an important extent.

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PubMed2002

Factor analysis of olfactory responses in Drosophila melanogaster enhancer-trap lines as a method for ascertaining common reception components for different odorants.

Olfactory information is transmitted to the brain using combinatorial receptor codes; consequently, a single reception element can be activated by different odorants. Several methods have been applied to describe from a functional point of view those odorants sharing olfactory reception components. A genetic approach in Drosophila melanogaster used correlation between behavioral responses to different odorants for deducing common olfactory pathway-genes. A factor analysis applied to behavioral responses to five odorants of 27 antennal enhancer-trap lines revealed three components, explaining 82.1% of the total observed variance. A first factor affects simultaneously the response to ethyl acetate, propionaldehyde, and acetone. A second factor was related to responses to ethyl acetate, ethyl alcohol, and acetone, and, finally, the third factor associates responses to acetic acid and ethyl acetate. They contribute by 35.1%, 36.9%, and 28%, respectively, to the explained variance.

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PubMedDate not supplied

High efficiency of a double-screening method on single P-element insertion lines to identify quantitative trait mutants in Drosophila melanogaster.

Enhancer trap P-element insertion has become a common method for generating new mutations in Drosophila melanogaster. When this method is used to isolate mutants for quantitative traits, an appropriate control must be established to define normal and mutant phenotypes. Considering that enhancer-trap lines are generated by crossing several strains, usually with no homogeneous genetic background, no clear control strain can be selected. Previous reports tried to overcome this problem by homogenizing the genetic background of the original lines. However, this is not the most common scenario, especially when functional phenotypes are studied in previously generated lines. Without such caution, is it possible to identify functional mutants among P-element insertion lines? We tested this for olfactory preference, a quantitative trait. Using as control measurement the average phenotype of 30 simultaneously generated P-element insertion lines with preferential reporter-gene expression in olfactory reception organs, we found that 25 of the lines exhibited mutant phenotypes in response to one or several of 5 tested odorants. Additional tests showed that the efficiency of the method for detecting olfactory mutations exceeded 60% even for such a small number of tested odorants. According to these results this approach greatly facilitates the identification of putative abnormal phenotypes, which must be extensively confirmed afterwards.

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