XRCC4-like factor (XLF) functions in classical non-homologous end-joining (cNHEJ) but is dispensable for the repair of DNA double-strand breaks (DSBs) generated during V(D)J recombination. A ...long-standing hypothesis proposes that, in addition to its canonical nuclease activity, the RAG1/2 proteins participate in the DNA repair phase of V(D)J recombination. Here we show that in the context of RAG2 lacking the C-terminus domain (Rag2(c/c) mice), XLF deficiency leads to a profound lymphopenia associated with a severe defect in V(D)J recombination and, in the absence of p53, increased genomic instability at V(D)J sites. In addition, Rag2(c/c) XLF(-/-) p53(-/-) mice develop aggressive pro-B cell lymphomas bearing complex chromosomal translocations and gene amplifications involving Igh and c-myc/pvt1 loci. Our results reveal an unanticipated functional interplay between the RAG complex and XLF in repairing RAG-induced DSBs and maintaining genome integrity during antigen receptor gene assembly.
Biallelic NF2 gene inactivation is common in sporadic and in neurofibromatosis type 2 (NF2)-related meningiomas. We show that, beginning at four months of age, thirty percent of mice with arachnoidal ...cell Cre-mediated excision of Nf2 exon 2 developed a range of meningioma subtypes histologically similar to the human tumors. Additional hemizygosity for p53 did not modify meningioma frequency or progression suggesting that Nf2 and p53 mutations do not synergize in meningeal tumorigenesis. This first mouse model initiated with a genetic lesion found in human meningiomas provides a powerful tool for investigating tumor progression and for the preclinical evaluation of therapeutic interventions.
Hemizygosity for the NF2 gene in humans causes a syndromic susceptibility to schwannoma development. However, Nf2 hemizygous mice do not develop schwannomas but mainly osteosarcomas. In the tumors of ...both species, the second Nf2 allele is inactivated. We report that conditional homozygous Nf2 knockout mice with Cre-mediated excision of Nf2 exon 2 in Schwann cells showed characteristics of neurofibromatosis type 2. These included schwannomas, Schwann cell hyperplasia, cataract, and osseous metaplasia. Thus, the tumor suppressor function of Nf2, here revealed in murine Schwann cells, was concealed in hemizygous Nf2 mice because of insufficient rate of second allele inactivation in this cell compartment. The finding of this conserved function documents the relevance of the present approach to model the human disease.
Abundant tau inclusions are a defining hallmark of several human neurodegenerative diseases, including Alzheimer's disease. Protein fragmentation is a widely observed event in neurodegenerative ...proteinopathies. The relevance of tau fragmentation for the neurodegenerative process in tauopathies has yet remained unclear. Here we found that co-expression of truncated and full-length human tau in mice provoked the formation of soluble high-molecular-weight tau, the failure of axonal transport, clumping of mitochondria, disruption of the Golgi apparatus and missorting of synaptic proteins. This was associated with extensive nerve cell dysfunction and severe paralysis by the age of 3 weeks. When the expression of truncated tau was halted, most mice recovered behaviorally and functionally. In contrast, co-expression of full-length tau isoforms did not result in paralysis. Truncated tau thus induces extensive but reversible neurotoxicity in the presence of full-length tau through the formation of nonfilamentous high-molecular-weight tau aggregates, in the absence of tau filaments. Targeting tau fragmentation may provide a novel approach for the treatment of human tauopathies.
•The use of ultra-short baseline (USBL) acoustic technique in subsea is explored.•Proposed method is built upon box-in estimation, which uses only the distance.•Redundant measurements and avoidance ...of angular errors aid in improving accuracy.•Proposed method involves, among others, offset transformation and M−estimation.•As a result, a marker buoy was positioned well within the desired accuracy of 10 m.
Positioning seabed objects in ultra-deep waters is critical in the mapping, exploration, and industrial exploitation of oceans. This paper presents research on a subsea wellhead positioning process for the marking of seabed positions and its subsequent as-built verification. The results indicate that the ultra-short baseline (USBL) acoustic technique can provide static positioning accuracy and precision comparable to those of a long-baseline method (LBL) and significantly reduces the time and cost of the offshore project. The new approach was tested at different stages of the process. First, an innovative offset transformation method, which increases the precision of alignments, was proposed, followed by a step-by-step procedure for determining the positions of marker buoys on the seabed based on spin tests and cardinal heading calibration. Finally, the M−estimation method, which has not yet been applied in subsea engineering, was implemented and proved to be a suitable alternative to the ordinary least squares method.
The Clarion-Clipperton Zone (CCZ) in the tropical East Pacific is a region of interest for deep-sea mining due to its underwater deposits of polymetallic nodules containing economically important ...metals such as nickel, copper, and cobalt. It is also a region of extensive baseline studies aiming to describe the state of the environment, including the biodiversity of the benthic fauna. An abundant component of the abyssal plain ecosystem consists of sessile fauna which encrusts polymetallic nodules and are vulnerable to potential impacts arising from exploitation activities, particularly removal of substrate. Therefore, this fauna is often considered to have key species whose genetic connectivity should be studied to assess their ecological resilience. One such species is Abyssoprimnoa gemina Cairns, 2015, a deep-sea coral from the CCZ whose presence in the Interoceanmetal Joint Organization (IOM) claim area has been confirmed during samplings. In this study, we used next-generation sequencing (NGS) to obtain the 18S nuclear rRNA gene and the complete mitochondrial genome of A. gemina from IOM exploration area. The mitogenome is 18,825 bp long and encodes for 14 protein coding genes, 2 rRNAs, and a single tRNA. The two phylogeny reconstructions derived from these data confirm previous studies and display A. gemina within a highly supported cluster of seven species whose mitogenomes are all colinear and of comparable size. This study also demonstrates the suitability of NGS for DNA barcoding of the benthic megafauna of the CCZ, which could become part of the IOM protocol for the assessment of population diversity and genetic connectivity in its claim area.
This paper presents an original method for the comminution of polymetallic nodules in a hydro-jet mill of our own design, having the water jet pressure in the range of 70-200 MPa. The best ...comminution results are ensured by equipping the mill with a water jet having a diameter d
= 0.7 mm and a comminution-homogenization tube having a diameter d
= 2.4 mm, and by setting a distance s = 10 mm from the outlet of the homogenization tube to the comminuting disc. Particles of concretions comminuted under such conditions are characterized by a fairly regular isometric shape and favorable morphology represented by intense development of the specific surface.
The repair of DNA double strand breaks (DSBs) by the non-homologous end-joining pathway (NHEJ) is central for the proper development of the adaptive immune system. This repair pathway involves eight ...factors, including XRCC4-like factor (XLF)/Cernunnos and the paralog of XRCC4 and XLF, PAXX non-homologous end-joining factor (PAXX). Xlf-/- and Paxx-/- mice are viable and exhibit only a mild immunophenotype. However, mice lacking both PAXX and XLF are embryonic lethal because postmitotic neurons undergo massive apoptosis in embryos. To decipher the roles of PAXX and XLF in both V(D)J recombination and immunoglobulin class switch recombination (CSR), here, using Cre/lox-specific deletion to prevent the double-KO embryonic lethality, we developed two mouse models of a conditional Xlf KO in a Paxx-/- background. Cre expressed under the control of the iVav or CD21 promoter enabled Xlf deletion in early hematopoietic progenitors and splenic mature B cells, respectively. We demonstrate the XLF and PAXX interplay during V(D)J recombination in vivo, but not during CSR for which PAXX appeared to be fully dispensable. A Xlf/Paxx-double KO in hematopoietic progenitors resulted in a shorter lifespan associated with the onset of thymic lymphomas, revealing a genome caretaking function of XLF/PAXX.
The Cu-binding β-amyloid precursor protein (APP), and the amyloid Aβ peptide have been proposed to play a role in physiological metal regulation. There is accumulating evidence of an unbalanced Cu ...homeostasis with a causative or diagnostic link to Alzheimer's disease. Whereas elevated Cu levels are observed in APP knockout mice, APP overexpression results in reduced Cu in transgenic mouse brain. Moreover, Cu induces a decrease in Aβ levels in APP-transfected cells in vitro. To investigate the influence of bioavailable Cu, transgenic APP23 mice received an oral treatment with Cu-supplemented sucrose-sweetened drinking water (1). Chronic APP overexpression per se reduced superoxide dismutase 1 activity in transgenic mouse brain, which could be restored to normal levels after Cu treatment (2). A significant increase of brain Cu indicated its bioavailability on Cu treatment in APP23 mice, whereas Cu levels remained unaffected in littermate controls (3). Cu treatment lowered endogenous CNS Aβ before a detectable reduction of amyloid plaques. Thus, APP23 mice reveal APP-induced alterations linked to Cu homeostasis, which can be reversed by addition of dietary Cu.
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