Enhancement of endogenous neurogenesis in ephrin-B3 deficient mice after transient focal cerebral ischemia

Cerebral ischemia stimulates endogenous neurogenesis. However, the functional relevance of this phenomenon remains unclear because of poor survival and low neuronal differentiation rates of newborn cells. Therefore, further studies on mechanisms regulating neurogenesis under ischemic conditions are required, among which ephrin-ligands and ephrin-receptors (Eph) are an interesting target. Although Eph/ephrin proteins like ephrin-B3 are known to negatively regulate neurogenesis under physiological conditions, their role in cerebral ischemia is largely unknown. We therefore studied neurogenesis, brain injury and functional outcome in ephrin-B3−/− (knockout) and ephrin-B3+/+ (wild-type) mice submitted to cerebral ischemia. Induction of stroke resulted in enhanced cell proliferation and neuronal differentiation around the lesion site of ephrin-B3−/− compared to ephrin-B3+/+ mice. However, prominent post-ischemic neurogenesis in ephrin-B3−/− mice was accompanied by significantly increased ischemic injury and motor coordination deficits that persisted up to 4 weeks. Ischemic injury in ephrin-B3−/− mice was associated with a caspase-3-dependent activation of the signal transducer and activator of transcription 1 (STAT1). Whereas inhibition of caspase-3 had no effect on brain injury in ephrin-B3+/+ animals, infarct size in ephrin-B3−/− mice was strongly reduced, suggesting that aggravated brain injury in these animals might involve a caspase-3-dependent activation of STAT1. In conclusion, post-ischemic neurogenesis in ephrin-B3−/− mice is strongly enhanced, but fails to contribute to functional recovery because of caspase-3-mediated aggravation of ischemic injury in these animals. Our results suggest that ephrin-B3 might be an interesting target for overcoming some of the limitations of further cell-based therapies in stroke

Moonlighting Proteins Hal3 and Vhs3 Form a Heteromeric PPCDC with Ykl088w in Yeast CoA Biosynthesis

Premi a l'excel·lència investigadora. 2010Unlike most other organisms, the essential five-step Coenzyme A biosynthetic pathway has not been fully resolved in yeast. Specifically, the gene(s) encoding the phosphopantothenoylcysteine decarboxylase (PPCDC) activity still remains unidentified. Sequence homology analyses suggest three candidates, namely Ykl088w, Hal3 and Vhs3, as putative PPCDC enzymes in Saccharomyces cerevisiae. Interestingly, Hal3 and Vhs3 have been characterized as negative regulatory subunits of the Ppz1 protein phosphatase. Here we show that YKL088w does not encode a third Ppz1 regulatory subunit, and that the essential roles of Ykl088w and the Hal3/Vhs3 pair are complementary, cannot be interchanged and can be attributed to PPCDC-related functions. We demonstrate that while known eukaryotic PPCDCs are homotrimers, the active yeast enzyme is a heterotrimer which consists of Ykl088w and Hal3/Vhs3 monomers that separately provides two essential catalytic residues. Our results unveil Hal3/Vhs3 as moonlighting proteins, involved in both CoA biosynthesis and protein phosphatase regulation

17β-Estradiol Prevents Early-Stage Atherosclerosis in Estrogen Receptor-Alpha Deficient Female Mice

Estrogen is atheroprotective and a high-affinity ligand for both known estrogen receptors, ERα and ERβ. However, the role of the ERα in early-stage atherosclerosis has not been directly investigated and is incompletely understood. ERα-deficient (ERα−/−) and wild-type (ERα+/+) female mice consuming an atherogenic diet were studied concurrent with estrogen replacement to distinguish the actions of 17β-estradiol (E2) from those of ERα on the development of early atherosclerotic lesions. Mice were ovariectomized and implanted with subcutaneous slow-release pellets designed to deliver 6 or 8 μg/day of exogenous 17β-estradiol (E2) for a period of up to 4 months. Ovariectomized mice (OVX) with placebo pellets (E2-deficient controls) were compared to mice with endogenous E2 (intact ovaries) and exogenous E2. Aortas were analyzed for lesion area, number, and distribution. Lipid and hormone levels were also determined. Compared to OVX, early lesion development was significantly (p < 0.001) attenuated by E2 with 55–64% reduction in lesion area by endogenous E2 and >90% reduction by exogenous E2. Compared to OVX, a decline in lesion number (2- to 4-fold) and lesser predilection (~4-fold) of lesion formation in the proximal aorta also occurred with E2. Lesion size, development, number, and distribution inversely correlated with circulating plasma E2 levels. However, atheroprotection was independent of ERα status, and E2 athero-protection in both genotypes was not explained by changes in plasma lipid levels (total cholesterol, triglyceride, and high-density lipoprotein cholesterol). The ERα is not essential for endogenous/exogenous E2-mediated protection against early-stage atherosclerosis. These observations have potentially significant implications for understanding the molecular and cellular mechanisms and timing of estrogen action in different estrogen receptor (ER) deletion murine models of atherosclerosis, as well as implications to human studies of ER polymorphisms and lipid metabolism. Our findings may contribute to future improved clinical decision-making concerning the use of hormone therapy

Sequencing of diverse mandarin, pummelo and orange genomes reveals complex history of admixture during citrus domestication

Cultivated citrus are selections from, or hybrids of, wild progenitor species whose identities and contributions to citrus domestication remain controversial. Here we sequence and compare citrus genomes-a high-quality reference haploid clementine genome and mandarin, pummelo, sweet-orange and sour-orange genomes-and show that cultivated types derive from two progenitor species. Although cultivated pummelos represent selections from one progenitor species, Citrus maxima, cultivated mandarins are introgressions of C. maxima into the ancestral mandarin species Citrus reticulata. The most widely cultivated citrus, sweet orange, is the offspring of previously admixed individuals, but sour orange is an F1 hybrid of pure C. maxima and C. reticulata parents, thus implying that wild mandarins were part of the early breeding germplasm. A Chinese wild 'mandarin' diverges substantially from C. reticulata, thus suggesting the possibility of other unrecognized wild citrus species. Understanding citrus phylogeny through genome analysis clarifies taxonomic relationships and facilitates sequence-directed genetic improvement. (Résumé d'auteur

Transcriptome analysis of rainbow trout in response to non-virion (NV) protein of viral haemorrhagic septicaemia virus (VHSV)

The non-virion (NV) protein of viral haemorrhagic septicaemia virus (VHSV), an economically important fish novirhabdovirus, has been implicated in the interference of some host innate mechanisms (i.e. apoptosis) in vitro. This work aimed to characterise the immune-related transcriptome changes in rainbow trout induced by NV protein that have not yet been established in vivo. For that purpose, immune-targeted microarrays were used to analyse the transcriptomes from head kidney and spleen of rainbow trout (Oncorhynchus mykiss) after injection of recombinant NV (rNV). Results showed the extensive downregulation (and in some cases upregulation) of many innate and adaptive immune response genes not related previously to VHSV infection. The newly identified genes belonged to VHSV-induced genes (vigs), tumour necrosis factors, Toll-like receptors, antigen processing and presentation, immune co-stimulatory molecules, interleukins, macrophage chemotaxis, transcription factors, etc. Classification of differentially downregulated genes into rainbow trout immune pathways identified stat1 and jun/atf1 transcription factor genes as the most representative of the multipath gene targets of rNV. Altogether, these results contribute to define the role and effects of NV in trout by orchestrating an immunosuppression of the innate immune responses for favouring viral replication upon VHSV infection. Finally, these transcriptome results open up the possibility to find out new strategies against VHSV and better understand the interrelationships between some immune pathways in trout. © 2015, Springer-Verlag Berlin Heidelberg