The offspring of marriage between two first cousins with the same reciprocal translocation t(2;7)(p11;q31)

Summary A marriage between two first cousins who have the same 2/7 balanced translocation is reported. The chromosome rearrangement was primarily detected in amniotic fluid cells cultured for prenatal chromosome analysis because of advanced maternal age. The translocation was also found in the couple's two normal children and in three other members of the family. The possible zygotic chromosome constitutions following 2:2 meiotic segregation in consanguineous parents with the same translocation are discussed.     

Mutational Analysis of the Yeast TRAPP Subunit Trs20p Identifies Roles in Endocytic Recycling and Sporulation

Trs20p is a subunit of the evolutionarily conserved TRAPP (TRAnsport Protein Particle) complex that mediates various aspects of membrane trafficking. Three TRAPP complexes have been identified in yeast with roles in ER-to-Golgi trafficking, post-Golgi and endosomal-to-Golgi transport and in autophagy. The role of Trs20p, which is essential for viability and a component of all three complexes, and how it might function within each TRAPP complex, has not been clarified to date. To begin to address the role of Trs20p we generated different mutants by random mutagenesis but, surprisingly, no defects were observed in diverse anterograde transport pathways or general secretion in Trs20 temperature-sensitive mutants. Instead, mutation of Trs20 led to defects in endocytic recycling and a block in sporulation/meiosis. The phenotypes of different mutants appear to be separable suggesting that the mutations affect the function of Trs20 in different TRAPP complexes.     

Light-modulation of nitrate reductase activity in leaves and roots of maize

The nuclear DNA content in ray cells from the 1-year-old vascular cambium of white ash ( Fraxinus americana L.) trees was determined at intervals during the annual cycle of cambial activity and dormancy by using Feulgen microspectrophotometry. By 10 September, these cells had entered dormancy in G₁ with a normal DNA distribution and a minimal average DNA content of 2.65 pg. The average amount of DNA increased to 3.51 pg by 30 November, remained at this elevated value until at least 30 March, when the cambium was still dormant, then declined to the minimum level on 1 May and 10 June, when the cells were mitotically active. The springtime decline appeared to occur both before and during cell division. Between 1 May and 10 June, the prophase (4C) and telophase (2C) DNA contents decreased significantly. The amount of nuclear DNA measured by microspectrophotometry was verified by using flow cytometry and image analysis. The results support the view that there is an annual oscillation in the nuclear genome size of shoot meristematic cells in tree species native to the northern temperate zone.     

HIV/gp120 decreases adult neural progenitor cell proliferation via checkpoint kinase-mediated cell-cycle withdrawal and G1 arrest

Impaired adult neurogenesis has been observed in several neurodegenerative diseases, including human immunodeficiency virus (HIV-1)-associated dementia (HAD). Here we report that the HIV-envelope glycoprotein gp120, which is associated with HAD pathogenesis, inhibits proliferation of adult neural progenitor cells (aNPCs) in vitro and in vivo in the dentate gyrus of the hippocampus of HIV/gp120-transgenic mice. We demonstrate that HIV/gp120 arrests cell-cycle progression of aNPCs at the G1 phase via a cascade consisting of p38 mitogen-activated protein kinase (MAPK) --> MAPK-activated protein kinase 2 (a cell-cycle checkpoint kinase) --> Cdc25B/C. Our findings define a molecular mechanism that compromises adult neurogenesis in this neurodegenerative disorder.     

Influenza virus and redox mediated cell signaling: a complex network of virus/host interaction

Several viruses, including influenza, induce an imbalance of intracellular redox state toward pro-oxidant conditions. Through different mechanisms these alterations contribute both to influenza virus replication and to the pathogenesis of virus-induced disease. At the same time, influenza virus activates several intracellular signaling pathways involved in important physiological functions of the cell. Interestingly, many of these pathways are finely regulated by small changes in intracellular redox state, and the virus-induced redox imbalance might also control viral replication through this mechanism. Here we review the main intracellular redox-sensitive pathways activated upon influenza infection and involved in regulating viral replication.     

Lysoplex: An efficient toolkit to detect DNA sequence variations in the autophagy-lysosomal pathway

The autophagy-lysosomal pathway (ALP) regulates cell homeostasis and plays a crucial role in human diseases, such as lysosomal storage disorders (LSDs) and common neurodegenerative diseases. Therefore, the identification of DNA sequence variations in genes involved in this pathway and their association with human diseases would have a significant impact on health. To this aim, we developed Lysoplex, a targeted next-generation sequencing (NGS) approach, which allowed us to obtain a uniform and accurate coding sequence coverage of a comprehensive set of 891 genes involved in lysosomal, endocytic, and autophagic pathways. Lysoplex was successfully validated on 14 different types of LSDs and then used to analyze 48 mutation-unknown patients with a clinical phenotype of neuronal ceroid lipofuscinosis (NCL), a genetically heterogeneous subtype of LSD. Lysoplex allowed us to identify pathogenic mutations in 67% of patients, most of whom had been unsuccessfully analyzed by several sequencing approaches. In addition, in 3 patients, we found potential disease-causing variants in novel NCL candidate genes. We then compared the variant detection power of Lysoplex with data derived from public whole exome sequencing (WES) efforts. On average, a 50% higher number of validated amino acid changes and truncating variations per gene were identified. Overall, we identified 61 truncating sequence variations and 488 missense variations with a high probability to cause loss of function in a total of 316 genes. Interestingly, some loss-of-function variations of genes involved in the ALP pathway were found in homozygosity in the normal population, suggesting that their role is not essential. Thus, Lysoplex provided a comprehensive catalog of sequence variants in ALP genes and allows the assessment of their relevance in cell biology as well as their contribution to human disease.     

Isotopic evidence for the occurrence of biological nitrification and nitrogen deposition processing in forest canopies

This study examines the role of tree canopies in processing atmospheric nitrogen (N_dep) for four forests in the United Kingdom subjected to different N_dep: Scots pine and beech stands under high N_dep (HN, 13–19 kg N ha^?1 yr^?1), compared to Scots pine and beech stands under low N_dep (LN, 9 kg N ha^?1 yr^?1). Changes of NO₃‐N and NH₄‐N concentrations in rainfall (RF) and throughfall (TF) together with a quadruple isotope approach, which combines δ¹⁸O, Δ¹⁷O and δ¹⁵N in NO₃^? and δ¹⁵N in NH₄⁺, were used to assess N transformations by the canopies. Generally, HN sites showed higher NH₄‐N and NO₃‐N concentrations in RF compared to the LN sites. Similar values of δ¹⁵N‐NO₃^? and δ¹⁸O in RF suggested similar source of atmospheric NO₃^? (i.e. local traffic), while more positive values for δ¹⁵N‐NH₄⁺ at HN compared to LN likely reflected the contribution of dry NH_x deposition from intensive local farming. The isotopic signatures of the N‐forms changed after interacting with tree canopies. Indeed, ¹⁵N‐enriched NH₄⁺ in TF compared to RF at all sites suggested that canopies played an important role in buffering dry N_dep also at the low N_dep site. Using two independent methods, based on δ¹⁸O and Δ¹⁷O, we quantified for the first time the proportion of NO₃^? in TF, which derived from nitrification occurring in tree canopies at the HN site. Specifically, for Scots pine, all the considered isotope approaches detected biological nitrification. By contrast for the beech, only using the mixing model with Δ¹⁷O, we were able to depict the occurrence of nitrification within canopies. Our study suggests that tree canopies play an active role in the N cycling within forest ecosystems. Processing of N_dep within canopies should not be neglected and needs further exploration, with the combination of multiple isotope tracers, with particular reference to Δ¹⁷O.     

The nuclear form of glutathione peroxidase 4 is associated with sperm nuclear matrix and is required for proper paternal chromatin decondensation at fertilization

The nuclear isoform of the selenoprotein Phospholipid Hydroperoxide Glutathione Peroxidase (nGPx4) is expressed in haploid male germ cells, contains several cysteines and is able to oxidize protein thiols, besides glutathione. In this study we have investigated the subnuclear localization of this isoform in isolated mouse male germ cells at different steps of maturation. Immunoblotting and confocal microscopy analyses of subnuclear fractions showed that nGPx4 is localized to the nuclear matrix together with well known markers of this subnuclear compartment like lamin B and topoisomerase IIβ at all stages of germ cell differentiation. The peculiar nGPx4 distribution was confirmed by both biochemical and morphological analyses of COS-1 cells overexpressing Flag-tagged nGPx4. To test the functional role of nGPx4 in the process of chromatin assembly, sperm isolated from the caput and the cauda epididymides of wild-type (WT) and genetically deficient in nGPx4 (nGPx4-KO) mice were analyzed in an in vitro chromatin decondensation assay. Results showed that sperm from nGPx4-KO mice were more prone to decondense than those from WT mice at all stages of epididymal maturation, providing conclusive evidence that nGPx4 is required for a correct sperm chromatin compaction. We next addressed the issue of whether the lack of nGPx4 impacts on early events occurring at fertilization. Indeed, in vitro fertilization experiments showed an acceleration of sperm chromatin dispersion in oocytes fertilized by nGpx4-KO sperm compared with control. Overall these data indicate that the absence of nGPx4 leads to sperm nuclear matrix/chromatin instability that may negatively affect the embryo development.