Rapid detection of sex chromosomal aneuploidies by QF-PCR: application in 200 men with severe oligozoospermia or azoospermia

Klinefelter syndrome is the most common genetic cause of severe male factor infertility. Cytogenetic evaluation of metaphase chromosomes generally has a long turnaround time. We describe a reliable molecular genetic method that can be completed in 2 working days to identify the presence of any extra X chromosomes. The quantitative fluorescent (QF) 5-plex PCR includes the amplification of amelogenin, which is present on both sex chromosomes in a biallelic form, a polymorphic short tandem repeat (STR) on the pseudoautosomal region of X and Y (X22), two polymorphic X-specific STRs (DXS6803, DXS6809), and a Y-specific marker (SY134), in a single tube. The presence of an extra X chromosome is recognized either by a supernumerary peak or an increased peak area based on criteria we have developed. The application of the method on 200 patients resulted in the identification of 14 patients (7%) with Klinefelter syndrome or a variant form (2 SRY-positive 46,XX men), as well as an additional patient with 47,XYY karyotype. The QF-PCR method, along with Y chromosome microdeletion testing, can be used as a first-step genetic analysis in azoospermic or severely oligozoospermic patients for the rapid identification of sex chromosome aneuploidies.     

Sam68 sequestration and partial loss of function are associated with splicing alterations in FXTAS patients

Fragile X‐associated Tremor/Ataxia Syndrome (FXTAS) is a neurodegenerative disorder caused by expansion of 55–200 CGG repeats in the 5′‐UTR of the FMR1 gene. FXTAS is characterized by action tremor, gait ataxia and impaired executive cognitive functioning. It has been proposed that FXTAS is caused by titration of RNA‐binding proteins by the expanded CGG repeats. Sam68 is an RNA‐binding protein involved in alternative splicing regulation and its ablation in mouse leads to motor coordination defects. Here, we report that mRNAs containing expanded CGG repeats form large and dynamic intranuclear RNA aggregates that recruit several RNA‐binding proteins sequentially, first Sam68, then hnRNP‐G and MBNL1. Importantly, Sam68 is sequestered by expanded CGG repeats and thereby loses its splicing‐regulatory function. Consequently, Sam68‐responsive splicing is altered in FXTAS patients. Finally, we found that regulation of Sam68 tyrosine phosphorylation modulates its localization within CGG aggregates and that tautomycin prevents both Sam68 and CGG RNA aggregate formation. Overall, these data support an RNA gain‐of‐function mechanism for FXTAS neuropathology, and suggest possible target routes for treatment options.     

A tetramer-octamer equilibrium in Mycobacterium leprae and Escherichia coli RuvA by analytical ultracentrifugation

In the context of the bacterial RuvABC system, RuvA protein binds to and is involved in the subsequent processing of a four-way DNA structure called Holliday junction that is formed during homologous recombination. Four crystal structures of RuvA from Escherichia coli (EcoRuvA) showed that it was tetrameric, while neutron scattering and two other crystal structures for RuvA from Mycobacterium leprae (MleRuvA) and EcoRuvA showed that it was an octamer. To clarify this discrepancy, sedimentation equilibrium experiments by analytical ultracentrifugation were carried out and the results showed that MleRuvA existed as a tetramer-octamer equilibrium between 0.2-0.5 mg/ml in 0.1 M NaCl with a dissociation constant of 4 muM, and is octameric at higher concentrations. The same experiments in 0.3 M NaCl showed that MleRuvA is a tetramer up to 3.5 mg/ml, indicating that salt bridges are involved in octamer formation. Sedimentation equilibrium experiments with EcoRuvA showed that it was tetrameric at low concentration in both salt buffers but the protein was insoluble at high-protein concentrations in 0.1 M NaCl. It is concluded that free RuvA exists in an equilibrium between tetrameric and octameric forms in the typical concentration range and buffer found in bacterial cells.     

Activity alters muscle reinnervation and terminal sprouting by reducing the number of Schwann cell pathways that grow to link synaptic sites

In partially denervated rodent muscle, terminal Schwann cells (TSCs) located at denervated end plates grow processes, some of which contact neighboring innervated end plates. Those processes that contact neighboring synapses (termed "bridges") appear to initiate nerve terminal sprouting and to guide the growth of the sprouts so that they reach and reinnervate denervated end plates. Studies conducted prior to knowledge of this potential involvement of Schwann cells showed that direct muscle stimulation inhibits terminal sprouting following partial denervation (Brown and Holland, 1979). We have investigated the possibility this inhibition results from an alteration in the growth of TSC processes. We find that stimulation of partially denervated rat soleus muscle does not alter the length or number of TSC processes but does reduce the number of TSC bridges. Stimulation also reduces the number of TSC bridges that form between end plates during reinnervation of a completely denervated muscle. The nerve processes ("escaped fibers") that normally grow onto TSC processes during reinnervation are also reduced in length. Therefore, stimulation alters at least two responses to denervation in muscles: (1) the ability of TSC processes to form or maintain bridges with innervated synaptic sites, and (2) the growth of axons along processes extended by TSCs.     

Spatio-temporal propagation of Ca2+ signals by cyclic ADP-ribose in 3T3 cells stimulated via purinergic P2Y receptors

The role of cyclic ADP-ribose in the amplification of subcellular and global Ca2+ signaling upon stimulation of P2Y purinergic receptors was studied in 3T3 fibroblasts. Either (1) 3T3 fibroblasts (CD38- cells), (2) 3T3 fibroblasts preloaded by incubation with extracellular cyclic ADP-ribose (cADPR), (3) 3T3 fibroblasts microinjected with ryanodine, or (4) 3T3 fibroblasts transfected to express the ADP-ribosyl cyclase CD38 (CD38+ cells) were used. Both preincubation with cADPR and CD38 expression resulted in comparable intracellular amounts of cyclic ADP-ribose (42.3 +/- 5.2 and 50.5 +/- 8.0 pmol/mg protein). P2Y receptor stimulation of CD38- cells yielded a small increase of intracellular Ca2+ concentration and a much higher Ca2+ signal in CD38-transfected cells, in cADPR-preloaded cells, or in cells microinjected with ryanodine. Confocal Ca2+ imaging revealed that stimulation of ryanodine receptors by cADPR or ryanodine amplified localized pacemaker Ca2+ signals with properties resembling Ca2+ quarks and triggered the propagation of such localized signals from the plasma membrane toward the internal environment, thereby initiating a global Ca2+ wave.     

Dachs: an unconventional myosin that functions downstream of Fat to regulate growth, affinity and gene expression in Drosophila

The dachs gene was first identified almost a century ago based on its requirements for appendage growth, but has been relatively little studied. Here, we describe the phenotypes of strong dachs mutations, report the cloning of the dachs gene, characterize the localization of Dachs protein, and investigate the relationship between Dachs and the Fat pathway. Mutation of dachs reduces, but does not abolish, the growth of legs and wings. dachs encodes an unconventional myosin that preferentially localizes to the membrane of imaginal disc cells. dachs mutations suppress the effects of fat mutations on gene expression, cell affinity and growth in imaginal discs. Dachs protein localization is influenced by Fat, Four-jointed and Dachsous, consistent with its genetic placement downstream of fat. However, dachs mutations have only mild tissue polarity phenotypes, and only partially suppress the tissue polarity defects of fat mutants. Our results implicate Dachs as a crucial downstream component of a Fat signaling pathway that influences growth, affinity and gene expression during development.     

Impact of Epstein-Barr virus co-infection on natural acquired Plasmodium vivax antibody response

BackgroundThe simultaneous infection of Plasmodium falciparum and Epstein-Barr virus (EBV) could promote the development of the aggressive endemic Burkitt’s Lymphoma (eBL) in children living in P. falciparum holoendemic areas. While it is well-established that eBL is not related to other human malaria parasites, the impact of EBV infection on the generation of human malaria immunity remains largely unexplored. Considering that this highly prevalent herpesvirus establishes a lifelong persistent infection on B-cells with possible influence on malaria immunity, we hypothesized that EBV co-infection could have impact on the naturally acquired antibody responses to P. vivax, the most widespread human malaria parasite.Methodology/Principal findingsThe study design involved three cross-sectional surveys at six-month intervals (baseline, 6 and 12 months) among long-term P. vivax exposed individuals living in the Amazon rainforest. The approach focused on a group of malaria-exposed individuals whose EBV-DNA (amplification of balf-5 gene) was persistently detected in the peripheral blood (PersV_DNA, n = 27), and an age-matched malaria-exposed group whose EBV-DNA could never be detected during the follow-up (NegV_DNA, n = 29). During the follow-up period, the serological detection of EBV antibodies to lytic/ latent viral antigens showed that IgG antibodies to viral capsid antigen (VCA-p18) were significantly different between groups (PersV_DNA > NegV_DNA). A panel of blood-stage P. vivax antigens covering a wide range of immunogenicity confirmed that in general PersV_DNA group showed low levels of antibodies as compared with NegV_DNA. Interestingly, more significant differences were observed to a novel DBPII immunogen, named DEKnull-2, which has been associated with long-term neutralizing antibody response. Differences between groups were less pronounced with blood-stage antigens (such as MSP1-19) whose levels can fluctuate according to malaria transmission.Conclusions/SignificanceIn a proof-of-concept study we provide evidence that a persistent detection of EBV-DNA in peripheral blood of adults in a P. vivax semi-immune population may impact the long-term immune response to major malaria vaccine candidates.     

Neutron crystallographic studies of T4 lysozyme at cryogenic temperature

Bacteriophage T4 lysozyme (T4L) has been used as a paradigm for seminal biophysical studies on protein structure, dynamics, and stability. Approximately 700 mutants of this protein and their respective complexes have been characterized by X‐ray crystallography; however, despite the high resolution diffraction limits attained in several studies, no hydrogen atoms were reported being visualized in the electron density maps. To address this, a 2.2 Å‐resolution neutron data set was collected at 80 K from a crystal of perdeuterated T4L pseudo‐wild type. We describe a near complete atomic structure of T4L, which includes the positions of 1737 hydrogen atoms determined by neutron crystallography. The cryogenic neutron model reveals explicit detail of the hydrogen bonding interactions in the protein, in addition to the protonation states of several important residues.