Vanishing chromosomal inversion clines in Drosophila subobscura from Chile: Is behavioral thermoregulation to blame?

Chromosomal inversion clines paralleling the long-standing ones in native Palearctic populations of Drosophila subobscura evolved swiftly after this species invaded the Americas in the late 1970s and early 1980s. However, the new clines did not consistently continue to converge on the Old World baseline. Our recent survey of Chilean populations of D. subobscura shows that inversion clines have faded or even changed sign with latitude. Here, we investigate the hypothesis that this fading of inversion clines might be due to the Bogert effect, namely, that flies' thermoregulatory behavior has eventually compensated for environmental variation in temperature, thus buffering selection on thermal-related traits. We show that latitudinal divergence in thermal preference (T-p) has evolved in Chile for females, with higher-latitude flies having a lower mean T-p. Plastic responses in T-p also lessen latitudinal thermal variation because flies developed at colder temperatures prefer warmer microclimates. Our results are consistent with the idea that active behavioral thermoregulation might buffer environmental variation and reduce the potential effect of thermal selection on other traits as chromosomal arrangements

Long-term changes in the inversion chromosomal polymorphism: Drosophila subobscura population from Rasht (North of Iran)

Drosophila subobscura is characterized by a rich chromosomal polymorphism for inversions. Many inversions are adaptive to global warming and can be classified as 'warm' or 'cold' adapted. However, most studies were carried out from European populations located in the central area of the species distribution or from American colonizing populations. For this reason, we aimed to analyse the isolated and marginal Rasht population, located in the Hyrcanian forests area (Iran). The chromosomal polymorphism for inversions was compared with previous Rasht samples (Rasht I and II) obtained 57 years ago. This polymorphism has changed regarding to the inversion composition and frequencies. Interestingly, the polymorphism for inversions was scarce and similar to that of Madeira, an isolated Atlantic island. Likely, this similarity is a consequence of the marginal location and isolation of Rasht population. Also, the CTI (Chromosomal Thermal Index) was 0.445, showing a significant increase over those from Rasht I (0.184) and II (0.210). All these observations were in agreement with global warming expectations. Moreover, the CTI was also computed for Russian Caucasus and Turkish populations collected more than forty years ago to better understand the adaptive potential of D. subobscura and to study the similarity between populations of different geographic areas. In summary, the inversions of D. subobscura changed also in marginal and isolated populations in agreement with global warming expectations, and an open question is to know where is the threshold for this evolutionary change

Global warming and chromosomal inversion adaptation in isolated islands: Drosophila subobscura populations from Madeira

Global warming is an environmental phenomenon to which species must adapt to survive. The chromosomal inversion polymorphism of Drosophila subobscura constitutes a genomic architecture that provides an adaptive capacity to this species. Until now, their populations studied were continental or in islands located near the coastline. In these conditions, gene flow could be a relevant mechanism allowing the movement of thermally adapted inversions between populations. For this reason, we obtained and compared the D. subobscura inversion polymorphism from Madeira, an Atlantic isolated island, with those reported there thirty eight and forty six years ago. Moreover, we studied whether global warming affected this island by measuring mean, maximum and minimum temperatures in a fifty-five years period. We detected significant increase of all these atmospheric parameters in agreement with climate change expectations. Focusing in thermal adapted inversions, their frequencies and the CTI (Chromosomal Thermal Index) values remained rather stable over years. Furthermore, J, U and O chromosomes almost present fixation for 'warm' adapted inversions. Thus, island populations of D. subobscura might be in the threshold of being endangered. However, apart from selection other evolutionary mechanism such as phenotypic plasticity or thermoregulatory behavior could be involved in the survival of the species populations. Finally, being a generalist species living in humanized environments could also favor the persistence of their Madeira populations

Distribution of the transposable elements bilbo and gypsy in original and colonizing populations of Drosophila subobscura

Background: Transposable elements (TEs) constitute a substantial amount of all eukaryotic genomes. They induce an important proportion of deleterious mutations by insertion into genes or gene regulatory regions. However, their mutational capabilities are not always adverse but can contribute to the genetic diversity and evolution of organisms. Knowledge of their distribution and activity in the genomes of populations under different environmental and demographic regimes, is important to understand their role in species evolution. In this work we study the chromosomal distribution of two TEs, gypsy and bilbo, in original and colonizing populations of Drosophila subobscura to reveal the putative effect of colonization on their insertion profile. Results: Chromosomal frequency distribution of two TEs in one original and three colonizing populations of D. subobscura, is different. Whereas the original population shows a low insertion frequency in most TE sites, colonizing populations have a mixture of high (frequency ≥ 10%) and low insertion sites for both TEs. Most highly occupied sites are coincident among colonizing populations and some of them are correlated to chromosomal arrangements. Comparisons of TE copy number between the X chromosome and autosomes show that gypsy occupancy seems to be controlled by negative selection, but bilbo one does not. Conclusion: These results are in accordance that TEs in Drosophila subobscura colonizing populations are submitted to a founder effect followed by genetic drift as a consequence of colonization. This would explain the high insertion frequencies of bilbo and gypsy in coincident sites of colonizing populations. High occupancy sites would represent insertion events prior to colonization. Sites of low frequency would be insertions that occurred after colonization and/or copies from the original population whose frequency is decreasing in colonizing populations. This work is a pioneer attempt to explain the chromosomal distribution of TEs in a colonizing species with high inversion polymorphism to reveal the putative effect of arrangements in TE insertion profiles. In general no associations between arrangements and TE have been found, except in a few cases where the association is very strong. Alternatively, founder drift effects, seem to play a leading role in TE genome distribution in colonizing populations

Annual climatic effects on the autumnal Drosophilids fauna composition at the Font Groga site (Tibidabo, Barcelona)

The abundance of different drosophilid species was studied in a series of six consecutive years during autumn at the Font Groga site (Tibidabo, Barcelona). Furthermore, the relation between these abundances and the following climatological variables (Tmean: mean temperature, Tmax: maximum temperature, Tmin: minimum temperature, Hm: mean humidity and Rf: rainfall) were studied. The most common species observed at this location were D. subobscura, D. melanogaster/D.simulans and the invasive species D. suzukii. Other species were trapped depending on the year (D. immigrans, D. buzzatti, D. cameraria, D. phalerata and D. hydei), and the values of several diversity indexes were computed for each annual collections. In general, in those years where D. melanogaster/D. simulans flies were abundant, D. subobscura and D. suzukii were in low frequencies. From the analyses of the climatic variables and the three most abundant species, it seemed that D. subobscura would need environmental conditions characterized by a low Tmin, not a very high Tmax (but with a large difference between both), a certain degree of humidity and scarce rainfall. D. suzukii presented a similar pattern, but not so accused, whereas D. melanogaster / D.simulans group would need high Tmin, low Tmax (with a small difference between Tmin and Tmax values) and low levels of humidity and rainfall. Finally, in these autumnal samples our results would indicate a certain association between the abundances of D. subobscura and D. suzukii, although their breeding sites are clearly different

Descritpion of a double mutant strain of Drosophila melanogaster useful for genetic laboratory courses.

Many years ago, individuals showing drastically reduced eyes arose in our laboratory e (ebony) strain (Bridges and Morgan, 1923). We selected those flies presenting both traits and constituted a new double mutant strain e su (e, ebony; su, 'sense ulls', eyes drastically reduced). Both mutations were linked and located in the chromosome III. We used this strain in linkage analyses with our undergraduate students. [...

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ABSTRACT. Objective. To determine the level of residual inflammation [synovitis, bone marrow edema (BME), tenosynovitis, and total inflammation] quantified by hand magnetic resonance imaging (h-MRI) in patients with rheumatoid arthritis (RA) in remission according to 3 different definitions of clinical remission, and to compare these remission definitions. Methods. A cross-sectional study. To assess the level of residual MRI inflammation in remission, cutoff levels associated to remission and median scores of MRI residual inflammatory lesions were calculated. Data from an MRI register of patients with RA who have various levels of disease activity were used. These were used for the analyses: synovitis, BME according to the Rheumatoid Arthritis Magnetic Resonance Imaging Scoring system, tenosynovitis, total inflammation, and disease activity composite measures recorded at the time of MRI. Receiver-operating characteristic analysis was used to identify the best cutoffs associated with remission for each inflammatory lesion on h-MRI. Median values of each inflammatory lesion for each definition of remission were also calculated. Results. A total of 388 h-MRI sets of patients with RA with different levels of disease activity, 130 in remission, were included. Cutoff values associated with remission according to the Simplified Disease Activity Index (SDAI) ≤ 3.3 and the Boolean American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) definitions for BME and tenosynovitis (1 and 3, respectively) were lower than BME and tenosynovitis (2 and 5, respectively) for the Disease Activity Score on 28 joints (DAS28) ≤ 2.6. Median scores for synovitis, BME, and total inflammation were also lower for the SDAI and Boolean ACR/EULAR remission criteria compared with DAS28. Conclusion. Patients with RA in remission according to the SDAI and Boolean ACR/EULAR definitions showed lower levels of MRI-detected residual inflammation compared with DAS28

Role of adipose tissue GLP-1R expression in metabolic improvement after bariatric surgery in patients with type 2 diabetes

We aimed to explore the relationship between GLP-1 receptor (GLP-1R) expression in adipose tissue (AT) and incretin secretion, glucose homeostasis and weight loss, in patients with morbid obesity and type 2 diabetes undergoing bariatric surgery. RNA was extracted from subcutaneous (SAT) and visceral (VAT) AT biopsies from 40 patients randomized to metabolic gastric bypass, sleeve gastrectomy or greater curvature plication. Biochemical parameters, fasting plasma insulin, glucagon and area under the curve (AUC) of GLP-1 following a standard meal test were determined before and 1 year after bariatric surgery. GLP-1R expression was higher in VAT than in SAT. GLP-1R expression in VAT correlated with weight (r = -0.453, p = 0.008), waist circumference (r = -0.494, p = 0.004), plasma insulin (r = -0.466, p = 0.007), and systolic blood pressure (BP) (r = -0.410, p = 0.018). At 1 year, GLP-1R expression in VAT was negatively associated with diastolic BP (r = -0.361, p = 0.039) and, following metabolic gastric bypass, with the increase of GLP-1 AUC, (R-2 = 0.46, p = 0.038). Finally, GLP-1R in AT was similar independently of diabetes outcomes and was not associated with weight loss after surgery. Thus, GLP-1R expression in AT is of limited value to predict incretin response and does not play a role in metabolic outcomes after bariatric surgery

HIV-1/HAART-Related Lipodystrophy Syndrome (HALS) Is Associated with Decreased Circulating sTWEAK Levels

Background and Objectives Obesity and HIV-1/HAART-associated lipodystrophy syndrome (HALS) share clinical, pathological and mechanistic features. Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a multifunctional cytokine that plays an important role in obesity and related diseases. We sought to explore the relationship between HALS and circulating levels of soluble (s) TWEAK and its scavenger receptor sCD163. Methods This was a cross-sectional multicenter study of 120 HIV-1-infected patients treated with a stable HAART regimen; 56 with overt HALS and 64 without HALS. Epidemiological and clinical variables were determined. Serum levels of sTWEAK and sCD163 levels were measured by ELISA. Results were analyzed with Student's t-test, Mann-Whitney U and χ2 test. Pearson and Spearman correlation were used to estimate the strength of association between variables. Results Circulating sTWEAK was significantly decreased in HALS patients compared with non-HALS patients (2.81±0.2 vs. 2.94±0.28 pg/mL, p = 0.018). No changes were observed in sCD163 levels in the studied cohorts. On multivariate analysis, a lower log sTWEAK concentration was independently associated with the presence of HALS (OR 0.027, 95% CI 0.001-0.521, p = 0.027). Conclusions HALS is associated with decreased sTWEAK levels

Adipose tissue mitochondrial dysfunction in human obesity is linked to a specific DNA methylation signature in adipose-derived stem cells

Background: A functional population of adipocyte precursors, termed adipose-derived stromal/stem cells (ASCs), is crucial for proper adipose tissue (AT) expansion, lipid handling, and prevention of lipotoxicity in response to chronic positive energy balance. We previously showed that obese human subjects contain a dysfunctional pool of ASCs. Elucidation of the mechanisms underlying abnormal ASC function might lead to therapeutic interventions for prevention of lipotoxicity by improving the adipogenic capacity of ASCs. Methods: Using epigenome-wide association studies, we explored the impact of obesity on the methylation signature of human ASCs and their differentiated counterparts. Mitochondrial phenotyping of lean and obese ASCs was performed. TBX15 loss- and gain-of-function experiments were carried out and western blotting and electron microscopy studies of mitochondria were performed in white AT biopsies from lean and obese individuals. Results: We found that DNA methylation in adipocyte precursors is significantly modified by the obese environment, and adipogenesis, inflammation, and immunosuppression were the most affected pathways. Also, we identified TBX15 as one of the most differentially hypomethylated genes in obese ASCs, and genetic experiments revealed that TBX15 is a regulator of mitochondrial mass in obese adipocytes. Accordingly, morphological analysis of AT from obese subjects showed an alteration of the mitochondrial network, with changes in mitochondrial shape and number. Conclusions: We identified a DNA methylation signature in adipocyte precursors associated with obesity, which has a significant impact on the metabolic phenotype of mature adipocytes