Effect of temperature on the expression of bobbed mutations in Drosophila melanogaster

The expression of two bobbed mutations on the X chromosome was studied at two temperatures 25 degrees C and 18 degrees C (larval developmental time, viability, phenotype of adult...). Results showed that the wm4bb mutation is thermosensitive. Some hypothesis are expressed to explain this phenomenon.     

Spatial and temporal genetic variation in Tunisian field populations of Macrosiphum euphorbiae (Thomas)

The potato aphid Macrosiphum euphorbiae (Thomas) is a major pest of several economic crops in Tunisia. Using 10 microsatellites, we analyzed five populations of M. euphorbiae sampled during the 2004-2005 solanaceous and cucurbit season (April through September) from five geographic origins. From 235 aphids, 61 different multilocus genotypes were identified of which three genotypes MLG1, MLG2, and MLG42 were predominant on all host plants and regions. MLG1 and MLG2 genotypes were detected in 2004 and did not reappear in spring 2005, while the genotype MLG42 was detected only in 2005. All populations showed significant deviation from Hardy-Weinberg equilibrium even in data sets including one individual per genotype. χ(2) independence tests and analysis of molecular variance showed no significant differentiation among populations collected on different host plant and from different geographic origin, but differences between populations from two successive years were significant. Factorial component analysis corroborates these results. The probable causes of this seasonal variation were discussed.     

Oral administration of levan polysaccharide reduces the alloxan-induced oxidative stress in rats

This study aimed to evaluate the effect of a polysaccharide named levan, which was produced by new isolated bacteria, on oxidative stress and hyperglycemia in alloxan-induced diabetic rats. Levan polysaccharide was given in drinking water for 60 days at a daily dose equivalent to 2%. The oral administration of levan in diabetic rats caused a decrease in glucose level in plasma and an increase of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activities in both pancreas and liver. Furthermore, a protective action against hepatic and pancreatic toxicity in diabetic rats was clearly observed. Furthermore, a significant decrease in hepatic and pancreatic indices toxicity was observed, i.e., alkalines phosphatases (ALP), aspartate and lactate transaminases (AST and ALT), lactate deshydrogenases (LDH) activities and the thiobarbituric acid-reactive substances (TBARs). These beneficial effects of levan were confirmed by histological findings in hepatic and pancreatic tissues of diabetic rats. This study demonstrates for the first time that levan is efficient in inhibiting hyperglycemia and oxidative stress induced by diabetes and suggests that administration of levan may be helpful in the prevention of diabetic complications associated with oxidative stress.     

The role of the Notch pathway in healthy and osteoarthritic articular cartilage: from experimental models to <Emphasis Type="Italic">ex vivo</Emphasis> studies

Osteoarthritis is the most prevalent form of arthritis in the world. With the progressive ageing of the population, it is becoming a major public health problem. The involvement of certain signaling pathways, such as the Notch pathway, during cartilage pathology has been reported. In this review, we report on studies that investigated the expression pattern of the Notch family members in articular cartilage and the eventual involvement of this pathway in the modulation of the physiology and pathology of chondrocytes. Temporal and/or spatial modulation of this signaling pathway may help these cells to synthesize a new functional extracellular matrix and restore the functional properties of the articular cartilage.     

A recurrent deletion of DPY19L2 causes infertility in man by blocking sperm head elongation and acrosome formation

An increasing number of couples require medical assistance to achieve a pregnancy, and more than 2% of the births in Western countries now result from assisted reproductive technologies. To identify genetic variants responsible for male infertility, we performed a whole-genome SNP scan on patients presenting with total globozoospermia, a primary infertility phenotype characterized by the presence of 100% round acrosomeless spermatozoa in the ejaculate. This strategy allowed us to identify in most patients (15/20) a 200 kb homozygous deletion encompassing only DPY19L2, which is highly expressed in the testis. Although there was no known function for DPY19L2 in humans, previous work indicated that its ortholog in C. elegans is involved in cell polarity. In man, the DPY19L2 region has been described as a copy-number variant (CNV) found to be duplicated and heterozygously deleted in healthy individuals. We show here that the breakpoints of the deletions are located on a highly homologous 28 kb low copy repeat (LCR) sequence present on each side of DPY19L2, indicating that the identified deletions were probably produced by nonallelic homologous recombination (NAHR) between these two regions. We demonstrate that patients with globozoospermia have a homozygous deletion of DPY19L2, thus indicating that DPY19L2 is necessary in men for sperm head elongation and acrosome formation. A molecular diagnosis can now be proposed to affected men; the presence of the deletion confirms the diagnosis of globozoospermia and assigns a poor prognosis for the success of in vitro fertilization.     

Role of the EphB2 receptor in autophagy,apoptosis and invasion in human breast cancer cells

The Eph and Ephrin proteins, which constitute the largest family of receptor tyrosine kinases, are involved in normal tissue development and cancer progression. Here, we examined the expression and role of the B-type Eph receptor EphB2 in breast cancers. By immunohistochemistry using a progression tissue microarray of human clinical samples, we found EphB2 to be expressed in benign tissues, but strongly increased in cancers particularly in invasive and metastatic carcinomas. Subsequently, we found evidence that EphB2, whose expression varies in established cell breast lines, possesses multiple functions. First, the use of a DOX-inducible system to restore EphB2 function to low expressers resulted in decreased tumor growth in vitro and in vivo, while its siRNA-mediated silencing in high expressers increased growth. This function involves the onset of apoptotic death paralleled by caspases 3 and 9 activation. Second, EphB2 was also found to induce autophagy, as assessed by immunofluorescence and/or immunoblotting examination of the LC3, ATG5 and ATG12 markers. Third, EphB2 also has a pro-invasive function in breast cancer cells that involves the regulation of MMP2 and MMP9 metalloproteases and can be blocked by treatment with respective neutralizing antibodies. Furthermore, EphB2-induced invasion is kinase-dependent and is impeded in cells expressing a kinase-dead mutant EphB2. In summary, we identified a mechanism involving a triple role for EphB2 in breast cancer progression, whereby it regulates apoptosis, autophagy, and invasion.     

Genetic Diversity of ND5 mitochondrial patterns in Ceratitis capitata (Diptera: Tephritidae) populations from Tunisia

The Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae) is known to be one of the most destructive and economically important agricultural pests worldwide. Several previous research projects have investigated the genetic makeup of regional populations of this pest and the relationships of populations from different areas of the world, including countries from the Mediterranean region. However, previously, little information has been reported on populations from Tunisia, despite the fact that this pest occurs in several agriculturally sensitive areas of this country. In order to study the genetic diversity of medfly populations within Tunisia, specimens were collected from the Coastal, Northern, Central and Southern regions of the country. Results using mitochondrial ND5 sequences show the presence of distinct haplotypes. This data used to analyze the levels of genetic variability within and between populations from Tunisia as well as from other countries in the Mediterranean region (Morocco and Israel) and in the world (Seychelles and Hawaii). This study also leads to a better understanding of the origin of new infestations and the colonization processes involving this pest.     

Detection of novel mitochondrial haplotype variants in populations of the Mediterranean fruit fly,Ceratitis capitata,from Tunisia,Israel and Morocco

The direct analysis of DNA sequence‐based mitochondrial haplotypes in individuals from populations of the Mediterranean fruit fly, Ceratitis capitata, from Tunisia, Morocco and Israel has revealed levels of genetic diversity that far exceed those previously described. A total of 33 distinct haplotypes were identified from 117 individuals representing seven populations from these countries. A network of haplotypes was constructed showing that we have captured essentially all of the sequence variations present in these populations for this gene. These results have important implications for future studies of the genetic structure of this and other closely related pest species.     

Aphid species identification using cuticular hydrocarbons and cytochrome b gene sequences

Abstract:  In Tunisia, four major aphid species have been identified based on adult female's morphological characters: Aphis gossypii Glover, Aphis craccivora Koch, Myzus persicae Sluzer and Macrosiphum euphorbiae Thomas. Species identification at individual collection sites is often difficult because adults are much fewer in number than larvae which are not so easy to distinguish morphologically. We therefore set up an experiment to determine if cuticular hydrocarbon phenotypes and mitochondrial DNA haplotypes could be used to distinguish such sympatric species. Results showed that each species had an unique cuticular hydrocarbon phenotype and mitochondrial cytochrome b sequence. Cytochrome b restriction fragment-length polymorphism markers, especially Dde I, identified in this sudy constitute a relatively simple and useful approach to distinguish the four species even at the nymphal stage.