Nek7 kinase is enriched at the centrosome, and is required for proper spindle assembly and mitotic progression

Members of the NIMA-related kinases (NRK) family are recently emerging as central regulators of various aspects of the cell cycle. However, the cellular roles of the mammalian NRK, Nek7, remain obscure. We show here that the endogenous Nek7 protein is enriched at the centrosome in a microtubule-independent manner. Overexpression of wt or kinase-defective Nek7 resulted in cells of rounder appearance, and higher proportions of multinuclear and apoptotic cells. Down-regulation of Nek7 using a small interfering RNA approach resulted in a significant increase in mitotic cells presenting multipolar spindle phenotype. These results suggest a role for Nek7 in regulating proper spindle assembly and mitotic progression.     

Molecular imaging of cell death in vivo by a novel small molecule probe

Apoptosis has a role in many medical disorders, therefore assessment of apoptosis in vivo can be highly useful for diagnosis, follow-up and evaluation of treatment efficacy. ApoSense is a novel technology, comprising low molecular-weight probes, specifically designed for imaging of cell death in vivo. In the current study we present targeting and imaging of cell death both in vitro and in vivo, utilizing NST-732, a member of the ApoSense family, comprising a fluorophore and a fluorine atom, for both fluorescent and future positron emission tomography (PET) studies using an ¹⁸F label, respectively. In vitro, NST-732 manifested selective and rapid accumulation within various cell types undergoing apoptosis. Its uptake was blocked by caspase inhibition, and occurred from the early stages of the apoptotic process, in parallel to binding of Annexin-V, caspase activation and alterations in mitochondrial membrane potential. In vivo, NST-732 manifested selective uptake into cells undergoing cell-death in several clinically-relevant models in rodents: (i) Cell-death induced in lymphoma by irradiation; (ii) Renal ischemia/reperfusion; (iii) Cerebral stroke. Uptake of NST-732 was well-correlated with histopathological assessment of cell-death. NST-732 therefore represents a novel class of small-molecule detectors of apoptosis, with potential useful applications in imaging of the cell death process both in vitro and in vivo. Revital Aloya and Anat Shirvan are equal contribution to the paper     

Maladaptation to mental stress mitigated by the adaptive immune system via depletion of naturally occurring regulatory CD4+CD25+ cells

Peripheral cellular immunity was recently shown to play a critical role in brain plasticity and performance. The antigenic specificity of the participating T cells, however, was not investigated, and nor was their relevance to psychological stress. Here we show, using a mouse model, that adaptive immunity mitigates maladaptation to the acute psychological stress known to trigger abnormal behaviors reminiscent of human post-traumatic stress disorder. Assessment of behavioral adaptation (measured by the acoustic startle response and avoidance behavior) in mice after their exposure to predator odor revealed that maladaptation was several times more prevalent in T cell-deficient mice than in their wild-type counterparts. A single population of T cells reactive to central nervous system (CNS)-associated self-protein was sufficient to endow immune-deficient mice with the ability to withstand the psychological stress. Naturally occurring CD4+CD25+ regulatory T cells were found to suppress this endogenous anti-stress attribute. These findings suggest that T cells specific to abundantly expressed CNS antigens are responsible for brain tissue homeostasis and help the individual to cope with stressful life episodes. They might also point the way to development of immune-based therapies for mental disorders, based either on up-regulation of T cells that partially cross-react with self-antigens or on weakening of the activity of regulatory T cells.     

Effects of intraleaf variations in carbonic anhydrase activity and gas exchange on leaf C18OO isoflux in Zea mays

Variation in the C18OO content of atmospheric CO2 (delta18Oa) can be used to distinguish photosynthesis from soil respiration, which is based on carbonic anhydrase (CA)-catalyzed 18O exchange between CO2 and 18O-enriched leaf water (delta18Ow). Here we tested the hypothesis that mean leaf delta18Ow and assimilation rates can be used to estimate whole-leaf C18OO flux (isoflux), ignoring intraleaf variations in CA activity and gas exchange parameters. We observed variations in CA activity along the leaf (> 30% decline from the leaf center toward the leaf ends), which were only partially correlated to those in delta18Ow (7 to 21 per thousand), delta18O and delta13C of leaf organic matter (25 to 30 per thousand and -12.8 to -13.2 per thousand, respectively), and substomatal CO2 concentrations (intercellular CO2 concentrations, c(i), at the leaf center were approximately 40% of those at the leaf tip). The combined effect of these variations produced a leaf-integrated isoflux that was different from that predicted based on bulk leaf values. However, because of canceling effects among the influencing parameters, isoflux overestimations were only approximately 10%. Conversely, use of measured parameters from a leaf segment could produce large errors in predicting leaf-integrated C18OO fluxes.     

Pelizaeus-Merzbacher-like disease caused by AIMP1/p43 homozygous mutation

Pelizaeus-Merzbacher disease is an X-linked hypomyelinating leukodystrophy caused by PLP1 mutations. A similar autosomal-recessive phenotype, Pelizaeus-Merzbacher-like disease (PMLD), has been shown to be caused by homozygous mutations in GJC2 or HSPD1. We report a consanguineous Israeli Bedouin kindred with clinical and radiological findings compatible with PMLD in which linkage to PLP1, GJC2, and HSPD1 was excluded. Through genome-wide homozygosity mapping and mutation analysis, we demonstrated in all affected individuals a homozygous frameshift mutation that fully abrogates the main active domain of AIMP1, encoding ARS-interacting multifunctional protein 1. The mutation fully segregates with the disease-associated phenotype and was not found in 250 Bedouin controls. Our findings are in line with the previously demonstrated inability of mutant mice lacking the AIMP1/p43 ortholog to maintain axon integrity in the central and peripheral neural system.     

Mutations disrupting selenocysteine formation cause progressive cerebello-cerebral atrophy

The essential micronutrient selenium is found in proteins as selenocysteine (Sec), the only genetically encoded amino acid whose biosynthesis occurs on its cognate tRNA in humans. In the final step of selenocysteine formation, the essential enzyme SepSecS catalyzes the conversion of Sep-tRNA to Sec-tRNA. We demonstrate that SepSecS mutations cause autosomal-recessive progressive cerebellocerebral atrophy (PCCA) in Jews of Iraqi and Moroccan ancestry. Both founder mutations, common in these two populations, disrupt the sole route to the biosynthesis of the 21st amino acid, Sec, and thus to the generation of selenoproteins in humans.