Biology subjects

Haase, A.

Publications and source records attributed to Haase, A..

22 records · Page 2Linked to original sources

bioRxiv2020

Increased prostaglandin-D2 in male but not female STAT3-deficient hearts shifts cardiac progenitor cells from endothelial to white adipocyte differentiation

Cardiac levels of the signal transducer and activator of transcription factor-3 (STAT3) decline with age, and male but not female mice with a cardiomyocyte-specific STAT3 deficiency (CKO) display premature age-related heart failure associated with reduced cardiac capillary density. In the present study isolated male and female CKO-cardiomyocytes exhibit increased prostaglandin (PG)-generating cyclooxygenase-2 (COX-2) expression. The PG-degrading hydroxyprostaglandin-dehydrogenase-15 (HPGD) expression is only reduced in male cardiomyocytes, which is associated with increased PGD2 secretion from isolated male but not female CKO-cardiomyocytes. Reduced HPGD expression in male cardiomyocytes derive from impaired androgen-receptor-(AR)-signaling due to loss of its co-factor STAT3. Elevated PGD2 secretion in males is associated with increased white adipocyte accumulation in aged male but not female hearts. Adipocyte differentiation is enhanced in isolated SCA-1+-cardiac-progenitor-cells (CPC) from young male CKO-mice compared to the adipocyte differentiation of male wildtype (WT)-CPC and CPC isolated from female mice. Epigenetic analysis in freshly isolated male CKO-CPC display hypermethylation in pro-angiogenic genes (Fgfr2, Epas1) and hypomethylation in the white adipocyte differentiation gene Zfp423 associated with upregulated ZFP423 expression and a shift from endothelial to white adipocyte differentiation compared to WT-CPC. The expression of the histone-methyltransferase EZH2 is reduced in male CKO-CPC compared to male WT-CPC whereas no differences in the EZH2 expression in female CPC were observed. Clonally expanded CPC can differentiate into endothelial cells or into adipocytes depending on the differentiation conditions. ZFP423 overexpression is sufficient to induce white adipocyte differentiation of clonal CPC. In isolated WT-CPC, PGD2 stimulation reduces the expression of EZH2 thereby upregulating ZFP423 expression and promoting white adipocyte differentiation. Thus, cardiomyocyte STAT3-deficiency leads to age-related and sex-specific cardiac remodeling and failure in part due to sex-specific alterations in PGD2 secretion and subsequent epigenetic impairment of the differentiation potential of CPC. Causally involved is the impaired AR signaling in absence of STAT3, which reduces the expression of the PG degrading enzyme HPGD.

cell biology↗

bioRxiv2019

Exploring multiple sensory systems in ovipositors of Drosophila suzukii and related species with different egg-laying behaviour

Drosophila suzukii is an invasive agricultural pest species that lays eggs in fruit during ripening, while most closely related Drosophila species use rotten matter as oviposition substrates. This behaviour is allowed by an enlarged and serrated ovipositor that can pierce intact fruit skin. D. suzukii combines multiple sensory systems (mechanosensation, olfaction, and taste) to select oviposition sites. Here, we test the hypothesis that the D. suzukii ovipositor is involved in these sensory modalities. We first investigate the ovipositor gene expression using a comparative framework of four Drosophila species with gradual changes in ovipositor morphology to identify evolutionary adaptations specific to D. suzukii. Results show transcription of chemoreceptors and mechanoreceptors in the four species, with a common core of sensory receptors expressed in all of them. Then, we demonstrate that sensory structures present in the distal tip of the D. suzukii ovipositor are mechanosensory-like sensilla, and that the degenerin/epithelial sodium channel ppk is expressed in homologous structures in Drosophila melanogaster. Our results suggest the D. suzukii ovipositor playing a role in mechanosensation, which might be shared with other Drosophila species.

zoology↗

bioRxiv2019

Automated quantification of synaptic boutons reveals their 3D distribution in the insect mushroom body

Synaptic boutons are highly plastic structures undergoing experience-dependent changes in their number, volume, and shape. Their plasticity has been intensively studied in the insect mushroom bodies by manually counting the number of boutons in small regions of interest and extrapolating this number to the volume of the mushroom body neuropil. Here we extend this analysis to the synaptic bouton distribution within a larger subregion of the mushroom body olfactory neuropil of honey bees (Apis mellifera). This required the development of an automated method combining two-photon imaging with advanced image post-processing and multiple threshold segmentation. The method was first validated in subregions of the mushroom body olfactory and visual neuropils. Further analyses in the olfactory neuropil suggested that previous studies overestimated the number of synaptic boutons. As a reason for that, we identified boundaries effects in the small volume samples. The application of the automated analysis to larger volumes of the mushroom body olfactory neuropil revealed a corrected average density of synaptic boutons and, for the first time, their 3D spatial distribution. This distribution exhibited a considerable heterogeneity. This additional information on the synaptic bouton distribution provides the basis for future studies on brain development, symmetry, and plasticity.

neuroscience↗

bioRxiv2017

Evolutionary compromises to environmental toxins: ammonia and urea tolerance in Drosophila suzukii and Drosophila melanogaster.

The invasive species Drosophila suzukii has evolved morphological and behavioral adaptations to lay eggs under the skin of fresh fruits. This results in severe damage of a wide range of small and stone fruits, thus making this species a serious agricultural and economical threat.\n\nDrosophila suzukii females typically lay few eggs per fruit, preferring not infested fruits. Hence larvae are exposed to a reduced amount of nitrogenous waste products. On the contrary, the innocuous Drosophila melanogaster lays eggs on fermented fruits already infested by conspecifics, with larvae developing in a crowded environment characterized by accumulation of nitrogenous waste such as ammonia and urea. Given these differences in oviposition and larval ecological niche, we expected different behavioral and physiological mechanisms in the two species to cope with nitrogenous waste. We investigated the impact of different concentrations of ammonia and urea on fecundity and larval development in both species. Females and larvae of D. suzukii showed a greater sensitivity to high concentration of both compounds, with a dramatic decrease in fecundity and egg viability.\n\nTo better understand the pathways underlying these differences, we evaluated the effect on ornithine aminotransferase and glutathione-S-transferase, two enzymes involved in nitrogen metabolism and stress response that are expressed during larval development. Under ammonia and urea exposure, the expression of these enzymes was significantly reduced in D. suzukii.\n\nThe fact that D. suzukiis shift from rotten to fresh fruit as oviposition and larval substrate resulted in less efficient detoxifying and excretory mechanisms represents a potential approach for its control. Fecundity and larval development are in fact dramatically impaired by nitrogen waste products. These findings can help in planning effective strategies of sustainable pest management that targets both females and larvae.

evolutionary biology↗