Dendritic cell differentiation and immune tolerance to insulin-related peptides in Igf2-deficient mice

There is some evidence that insulin-like growth factor 2 (IGF-2) may intervene in the control of T cell differentiation. To further study the immunoregulatory function of this growth factor, we analyzed the immune system of Igf2-/- mice. Phenotypically, some immunological parameters such as lymphoid organ morphology and cellularity were unaltered in Igf2-/- mice, but an increase of CD8+ cells and a decrease of B220+ cells were observed in spleen. In vitro, the development of bone marrow-derived dendritic cells was affected by the absence of Igf2 expression. After maturation, a higher percentage of immature dendritic cells was observed in Igf2-/- population, together with a secondary decrease in allogenic T cell proliferation. Activation of T cells was also affected by the lack of expression of this growth factor. The profile of B cell response in mutant mice immunized with IGF-2 evidenced a T-dependent profile of anti-IGF-2 Abs that was absent in Igf2+/+ mice. The influence of IGF-2 upon tolerance to insulin was also assessed in this model, and this showed that IGF-2 also intervenes in tolerance to insulin. The presence of a T-dependent response in Igf2-deficient mice should allow cloning of specific "forbidden" T CD4+ lymphocytes directed against IGF-2, as well as further investigation of their possible pathogenic properties against insulin family.     

Deletion 17q12 is a recurrent copy number variant that confers high risk of autism and schizophrenia

Autism spectrum disorders (ASD) and schizophrenia are neurodevelopmental disorders for which recent evidence indicates an important etiologic role for rare copy number variants (CNVs) and suggests common genetic mechanisms. We performed cytogenomic array analysis in a discovery sample of patients with neurodevelopmental disorders referred for clinical testing. We detected a recurrent 1.4 Mb deletion at 17q12, which harbors HNF1B, the gene responsible for renal cysts and diabetes syndrome (RCAD), in 18/15,749 patients, including several with ASD, but 0/4,519 controls. We identified additional shared phenotypic features among nine patients available for clinical assessment, including macrocephaly, characteristic facial features, renal anomalies, and neurocognitive impairments. In a large follow-up sample, the same deletion was identified in 2/1,182 ASD/neurocognitive impairment and in 4/6,340 schizophrenia patients, but in 0/47,929 controls (corrected p = 7.37 × 10⁻⁵). These data demonstrate that deletion 17q12 is a recurrent, pathogenic CNV that confers a very high risk for ASD and schizophrenia and show that one or more of the 15 genes in the deleted interval is dosage sensitive and essential for normal brain development and function. In addition, the phenotypic features of patients with this CNV are consistent with a contiguous gene syndrome that extends beyond RCAD, which is caused by HNF1B mutations only.     

Abnormal B-cell responses to chemokines, disturbed plasma cell localization, and distorted immune tissue architecture in Rgs1-/- mice

Normal lymphoid tissue development and function depend upon chemokine-directed cell migration. Since chemokines signal through heterotrimeric G-protein-coupled receptors, RGS proteins, which act as GTPase-activating proteins for Galpha subunits, likely fine tune the cellular responses to chemokines. Here we show that Rgs1(-/-) mice possess B cells that respond excessively and desensitize improperly to the chemokines CXCL12 and CXCL13. Many of the B-cell follicles in the spleens of Rgs1(-/-) mice have germinal centers even in the absence of immune stimulation. Furthermore, immunization of these mice leads to exaggerated germinal center formation; partial disruption of the normal architecture of the spleen and Peyer's patches; and abnormal trafficking of immunoglobulin-secreting cells. These results reveal the importance of a regulatory mechanism that limits and desensitizes chemokine receptor signaling.     

Hypertension Is a Conditional Factor for the Development of Cardiac Hypertrophy in Type 2 Diabetic Mice

Background

Type 2 diabetes is frequently associated with co-morbidities, including hypertension. Here we investigated if hypertension is a critical factor in myocardial remodeling and the development of cardiac dysfunction in type 2 diabetic db/db mice.

Methods

Thereto, 14-wks-old male db/db mice and non-diabetic db/+ mice received vehicle or angiotensin II (AngII) for 4 wks to induce mild hypertension (n = 9–10 per group). Left ventricular (LV) function was assessed by serial echocardiography and during a dobutamine stress test. LV tissue was subjected to molecular and (immuno)histochemical analysis to assess effects on hypertrophy, fibrosis and inflammation.

Results

Vehicle-treated diabetic mice neither displayed marked myocardial structural remodeling nor cardiac dysfunction. AngII-treatment did not affect body weight and fasting glucose levels, and induced a comparable increase in blood pressure in diabetic and control mice. Nonetheless, AngII-induced LV hypertrophy was significantly more pronounced in diabetic than in control mice as assessed by LV mass (increase +51% and +34%, respectively, p<0.01) and cardiomyocyte size (+53% and +31%, p<0.001). This was associated with enhanced LV mRNA expression of markers of hypertrophy and fibrosis and reduced activation of AMP-activated protein kinase (AMPK), while accumulation of Advanced Glycation End products (AGEs) and the expression levels of markers of inflammation were not altered. Moreover, AngII-treatment reduced LV fractional shortening and contractility in diabetic mice, but not in control mice.

Conclusions

Collectively, the present findings indicate that type 2 diabetes in its early stage is not yet associated with adverse cardiac structural changes, but already renders the heart more susceptible to hypertension-induced hypertrophic remodeling.     

Disruption of the mitotic kinesin Eg5 gene (Knsl1) results in early embryonic lethality

Eg5, a member of the widely conserved kinesin-5 family, is a plus-end-directed motor involved in separation of centrosomes, and in bipolar spindle formation and maintenance during mitosis in vertebrates. To investigate the requirement for Eg5 in mammalian development, we have generated Eg5 deficient mice by gene targeting. Heterozygous mice are healthy, fertile, and show no detectable phenotype, whereas Eg5^−/− embryos die during early embryogenesis, prior to the implantation stage. This result shows that Eg5 is essential during early mouse development and cannot be compensated by another molecular motor.     

Highly contrasted population genetic structures in a host–parasite pair in the Caribbean Sea

Evolution and population genetic structure of marine species across the Caribbean Sea are shaped by two complex factors: the geological history and the present pattern of marine currents. Characterizing and comparing the genetic structures of codistributed species, such as host–parasite associations, allow discriminating the relative importance of environmental factors and life history traits that influenced gene flow and demographic events. Using microsatellite and Cytochrome Oxidase I markers, we investigated if a host–parasite pair (the heart urchin Meoma ventricosa and its parasitic pea crab Dissodactylus primitivus) exhibits comparable population genetic structures in the Caribbean Sea and how the observed patterns match connectivity regions from predictive models and other taxa. Highly contrasting patterns were found: the host showed genetic homogeneity across the whole studied area, whereas the parasite displayed significant differentiation at regional and local scales. The genetic diversity of the parasitic crabs (both in microsatellites and COI) was distributed in two main groups, Panama–Jamaica–St Croix on the one hand, and the South‐Eastern Caribbean on the other. At a smaller geographical scale, Panamanian and Jamaican parasite populations were genetically more similar, while more genetic differentiation was found within the Lesser Antilles. Both species showed a signature of population expansion during the Quaternary. Some results match predictive models or data from previous studies (e.g., the Western‐Eastern dichotomy in the parasite) while others do not (e.g., genetic differentiation within the Lesser Antilles). The sharp dissimilarity of genetic structure of these codistributed species outlines the importance of population expansion events and/or contrasted patterns of gene flow. This might be linked to differences in several life history traits such as fecundity (higher for the host), swimming capacity of larval stages (higher for the parasite), and habitat availability (higher for the host).     

Sequences homologous to Tc(s) transposable elements ofCaenorhabditis elegans are widely distributed in the phylum nematoda

Summary To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements fromCaenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found inCaenorhabditis and inTeratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and inBursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited toC. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history.     

PCR-RFLP analysis of chitinase genes enables efficient genotyping of Metarhizium anisopliae var. anisopliae

A new genotyping tool has been developed and evaluated for Metarhizium anisopliae var. anisopliae. The tool is based on Restriction Fragment Length Polymorphism (RFLP) analysis of three chitinase genes that are functionally linked to insect-pathogenicity of this fungus. It allowed for discrimination of 14 genotypes among 22 M. anisopliae var. anisopliae strains of a world wide collection. Analyses revealed that the approach may also be applicable to other Metarhizium varieties. The new tool will be useful for genetic characterization of M. anisopliae var. anisopliae strains, and it is applicable for laboratories with limited access to molecular diagnostic equipment.