Hormones and Sex-Specific Transcription Factors Jointly Control Yolk Protein Synthesis in Musca domestica

In the housefly Musca domestica, synthesis of yolk proteins (YPs) depends on the level of circulating ecdysteroid hormones. In female houseflies, the ecdysterone concentration in the hemolymph oscillates and, at high levels, is followed by expression of YP. In male houseflies, the ecdysterone titre is constantly low and no YP is produced. In some strains, which are mutant in key components of the sex-determining pathway, males express YP even though their ecdysterone titre is not significantly elevated. However, we find that these males express a substantial amount of the female variant of the Musca doublesex homologue, Md-dsx. The dsx gene is known to sex-specifically control transcription of yp genes in the fat body of Drosophila melanogaster. Our data suggest that Md-dsx also contributes to the regulation of YP expression in the housefly by modulating the responsiveness of YP-producing cells to hormonal stimuli

Paucity and preferential suppression of transgenes in late replication domains of the D. melanogaster genome

<p>Abstract</p> <p>Background</p> <p>Eukaryotic genomes are organized in extended domains with distinct features intimately linking genome structure, replication pattern and chromatin state. Recently we identified a set of long late replicating euchromatic regions that are underreplicated in salivary gland polytene chromosomes of <it>D. melanogaster</it>.</p> <p>Results</p> <p>Here we demonstrate that these underreplicated regions (URs) have a low density of <it>P</it>-<it>element </it>and <it>piggyBac </it>insertions compared to the genome average or neighboring regions. In contrast, <it>Minos</it>-based transposons show no paucity in URs but have a strong bias to testis-specific genes. We estimated the suppression level in 2,852 stocks carrying a single <it>P</it>-<it>element </it>by analysis of eye color determined by the mini-<it>white </it>marker gene and demonstrate that the proportion of suppressed transgenes in URs is more than three times higher than in the flanking regions or the genomic average. The suppressed transgenes reside in intergenic, genic or promoter regions of the annotated genes. We speculate that the low insertion frequency of <it>P-elemen</it>ts and <it>piggyBac</it>s in URs partially results from suppression of transgenes that potentially could prevent identification of transgenes due to complete suppression of the marker gene. In a similar manner, the proportion of suppressed transgenes is higher in loci replicating late or very late in Kc cells and these loci have a lower density of <it>P-elements </it>and <it>piggyBac </it>insertions. In transgenes with two marker genes suppression of mini-<it>white </it>gene in eye coincides with suppression of <it>yellow </it>gene in bristles.</p> <p>Conclusions</p> <p>Our results suggest that the late replication domains have a high inactivation potential apparently linked to the silenced or closed chromatin state in these regions, and that such inactivation potential is largely maintained in different tissues.</p

[18F]DPA-714: Direct Comparison with [11C]PK11195 in a Model of Cerebral Ischemia in Rats

PURPOSE: Neuroinflammation is involved in several brain disorders and can be monitored through expression of the translocator protein 18 kDa (TSPO) on activated microglia. In recent years, several new PET radioligands for TSPO have been evaluated in disease models. [(18)F]DPA-714 is a TSPO radiotracer with great promise; however results vary between different experimental models of neuroinflammation. To further examine the potential of [(18)F]DPA-714, it was compared directly to [(11)C]PK11195 in experimental cerebral ischaemia in rats. METHODS: Under anaesthesia, the middle cerebral artery of adult rats was occluded for 60 min using the filament model. Rats were allowed recovery for 5 to 7 days before one hour dynamic PET scans with [(11)C]PK11195 and/or [(18)F]DPA-714 under anaesthesia. RESULTS: Uptake of [(11)C]PK11195 vs [(18)F]DPA-714 in the ischemic lesion was similar (core/contralateral ratio: 2.84±0.67 vs 2.28±0.34 respectively), but severity of the brain ischemia and hence ligand uptake in the lesion appeared to vary greatly between animals scanned with [(11)C]PK11195 or with [(18)F]DPA-714. To solve this issue of inter-individual variability, we performed a direct comparison of [(11)C]PK11195 and [(18)F]DPA-714 by scanning the same animals sequentially with both tracers within 24 h. In this direct comparison, the core/contralateral ratio (3.35±1.21 vs 4.66±2.50 for [(11)C]PK11195 vs [(18)F]DPA-714 respectively) showed a significantly better signal-to-noise ratio (1.6 (1.3–1.9, 95%CI) fold by linear regression) for [(18)F]DPA-714. CONCLUSIONS: In a clinically relevant model of neuroinflammation, uptake for both radiotracers appeared to be similar at first, but a high variability was observed in our model. Therefore, to truly compare tracers in such models, we performed scans with both tracers in the same animals. By doing so, our result demonstrated that [(18)F]DPA-714 displayed a higher signal-to-noise ratio than [(11)C]PK11195. Our results suggest that, with the longer half-life of [(18)F] which facilitates distribution of the tracer across PET centre, [(18)F]DPA-714 is a good alternative for TSPO imaging

Time-activity curves of [¹¹C]PK11195 (A and C) and [¹⁸F]DPA-714 (B and D) in the core of the lesion and the contralateral area (animals with visible infarct only) (A, B: HIDAC PET scanner, single tracer and dual scans pooled; C, D: Inveon PET-CT scanner).

<p>Time-activity curves of [¹¹C]PK11195 (A and C) and [¹⁸F]DPA-714 (B and D) in the core of the lesion and the contralateral area (animals with visible infarct only) (A, B: HIDAC PET scanner, single tracer and dual scans pooled; C, D: Inveon PET-CT scanner).</p

[¹¹C]PK11195 and [¹⁸F]DPA-714 mean uptake values between 20 and 60 min post-injection (expressed as percentage of injected dose per cm³, mean±SD (A) and Core/contralateral ROIs ratio (B)) of the 7 animals scanned with both tracers successively within 24 h (2 animals with no lesion are not shown on these graphs, although there exclusion did not affect the outcome of the statistical analysis).

<p>* Significantly different from [¹¹C]PK11195 values, # significantly different from the contralateral side of the same tracer (Wilcoxon paired test, p<0.05). (<b>C</b>) Correlation between [¹¹C]PK11195 and [¹⁸F]DPA-714 core/contralateral ROIs ratio (all animals included) (dotted line = 95% confidence interval). (<b>D</b>) On the left of each panel, PET images shown are summed images between 20 and 60 min after injection of [¹¹C]PK11195 (left panel) and [¹⁸F]DPA-714 (right panel) co-registered with the MRI template. The ROIs automatically segmented from the corresponding PET images are shown on the right part of each panel. The ROIs are: infarct core (red; ROI covering the infarct in the MCAO territory and/or with the highest uptake), edge-1 (orange; ROI around the MCAO territory and/or with the 2^nd highest uptake), edge-2 (yellow; ROI around the MCAO territory and/or with the 3^rd highest uptake), contralateral ROI (green; ROI with the lowest uptake) and skull edges (white; 5^th ROI segmented in some animals, located on the edge of the skull, this ROI was not included in the statistical analysis).</p