206 research outputs found
Impaired precursor B cell differentiation in Bruton's tyrosine kinase-deficient mice
Bruton's tyrosine kinase (Btk) is a cytoplasmic signaling molecule that is
crucial for precursor (pre-B) cell differentiation in humans. In this
study, we show that during the transition of large cycling to small
resting pre-B cells in the mouse, Btk-deficient cells failed to
efficiently modulate the expression of CD43, surrogate L chain, CD2, and
CD25. In an analysis of the kinetics of pre-B cell differentiation in
vivo, Btk-deficient cells manifested a specific developmental delay within
the small pre-B cell compartment of about 3 h, when compared with
wild-type cells. Likewise, in in vitro bone marrow cultures, Btk-deficient
large cycling pre-B cells showed increased IL-7 mediated expansion and
reduced developmental progression into noncycling CD2(+)CD25(+) surrogate
L chain-negative small pre-B cells and subsequently into Ig-positive B
cells. Furthermore, the absence of Btk resulted in increased proliferative
responses to IL-7 in recombination-activating gene-1-deficient pro-B
cells. These findings identify a novel role for Btk in the regulation of
the differentiation stage-specific modulation of IL-7 responsiveness in
pro-B and pre-B cells. Moreover, our results show that Btk is critical for
an efficient transit through the small pre-B cell compartment, thereby
regulating cell surface phenotype changes during the developmental
progression of cytoplasmic mu H chain expressing pre-B cells into immature
IgM(+) B cells
Function of Bruton's tyrosine kinase during B cell development is partially independent of its catalytic activity
The Tec family member Bruton's tyrosine kinase (Btk) is a cytoplasmic
protein tyrosine kinase that transduces signals from the pre-B and B cell
receptor (BCR). Btk is involved in pre-B cell maturation by regulating
IL-7 responsiveness, cell surface phenotype changes, and the activation of
lambda L chain gene rearrangements. In mature B cells, Btk is essential
for BCR-mediated proliferation and survival. Upon BCR stimulation, Btk is
transphosphorylated at position Y551, which promotes its catalytic
activity and subsequently results in autophosphorylation at position Y223
in the Src homology 3 domain. To address the significance of Y223
autophosphorylation and the requirement of enzymatic activity for Btk
function in vivo, we generated transgenic mice that express the
autophosphorylation site mutant Y223F and the kinase-inactive mutant
K430R, respectively. We found that Y223 autophosphorylation was not
required for the regulation of IL-7 responsiveness and cell surface
phenotype changes in differentiating pre-B cells, or for peripheral B cell
differentiation. However, expression of the Y223F-Btk transgene could not
fully rescue the reduction of lambda L chain usage in Btk-deficient mice.
In contrast, transgenic expression of kinase-inactive K430R-Btk completely
reconstituted lambda usage in Btk-deficient mice, but the defective
modulation of pre-B cell surface markers, peripheral B cell survival, and
BCR-mediated NF-kappaB induction were partially corrected. From these
findings, we conclude that: 1) autophosphorylation at position Y223 is not
essential for Btk function in vivo, except for regulation of lambda L
chain usage, and 2) during B cell development, Btk partially acts as an
adapter molecule, independent of its catalytic activity
Recent progress on the manipulation of single atoms in optical tweezers for quantum computing
This paper summarizes our recent progress towards using single rubidium atoms
trapped in an optical tweezer to encode quantum information. We demonstrate
single qubit rotations on this system and measure the coherence of the qubit.
We move the quantum bit over distances of tens of microns and show that the
coherence is reserved. We also transfer a qubit atom between two tweezers and
show no loss of coherence. Finally, we describe our progress towards
conditional entanglement of two atoms by photon emission and two-photon
interferences.Comment: Proceedings of the ICOLS07 conferenc
VAMP8-mediated NOX2 recruitment to endosomes is necessary for antigen release
Contains fulltext :
178043.pdf (publisher's version ) (Open Access)Cross-presentation of foreign antigen in major histocompatibility complex (MHC) class I by dendritic cells (DCs) requires activation of the NADPH-oxidase NOX2 complex. We recently showed that NOX2 is recruited to phagosomes by the SNARE protein VAMP8 where NOX2-produced reactive oxygen species (ROS) cause lipid oxidation and membrane disruption, promoting antigen translocation into the cytosol for cross-presentation. In this study, we extend these findings by showing that VAMP8 is also involved in NOX2 trafficking to endosomes. Moreover, we demonstrate in both human and mouse DCs that absence of VAMP8 leads to decreased ROS production, lipid peroxidation and antigen translocation, and that this impairs cross-presentation. In contrast, knockdown of VAMP8 did not affect recruitment of MHC class I and the transporter associated with antigen processing 1 (TAP1) to phagosomes, although surface levels of MHC class I were reduced. Thus, in addition to a secretory role, VAMP8-mediates trafficking of NOX2 to endosomes and phagosomes and this promotes induction of cytolytic T cell immune responses
Using animations to connect macroscopic, sub-microscopic, and symbolic representations of the world
PROBLEM
Chemistry is considered a difficult subject mainly due to multiplicity of representations, i.e. the Johnstone’s triangle of macroscopic, sub-microscopic, and symbolic domains (Johnstone, 1982). When students learn chemistry, moving between these domains is a well-recognised challenge (Cardellini, 2012).
PLAN
Teaching resources must address all three domains. For example, sub-microscopic level can be represented by cartoons, macroscopic level by video recordings of laboratory experiments, and symbolic by chemical reactions and mathematical calculations.
ACTION
To address this challenge, we developed a series of animations to illustrate the chemical phenomena most difficult for students. They were accompanied with the audio and text narration designed to get students to address their assumptions and misconceptions and to assist hearing-impaired and non-English speakers. The animations were evaluated using engagement analytics, test results, and student/academic comments.
REFLECTION
To develop these animations, we combined evidence-based pedagogy and technology, to improve student learning and enrich student experience. Animations address shifting expectations of our students by providing them with learner-centred approaches to enhance learning engagement and impact. Teaching and learning with animations is flexible and self-paced
Tumor suppressor function of Bruton tyrosine kinase is independent of its catalytic activity
During B-cell development in the mouse, Bruton tyrosine kinase (Btk) and
the adaptor protein SLP-65 (Src homology 2 [SH2] domain-containing
leukocyte protein of 65 kDa) limit the expansion and promote the
differentiation of pre-B cells. Btk is thought to mainly function by
phosphorylating phospholipase Cgamma2, which is brought into close
proximity of Btk by SLP-65. However, this model was recently challenged by
the identification of a role for Btk as a tumor suppressor in the absence
of SLP-65 and by the finding that Btk function is partially independent of
its kinase activity. To investigate if enzymatic activity is critical for
the tumor suppressor function of Btk, we crossed transgenic mice
expressing the kinase-inactive K430R-Btk mutant onto a Btk/SLP-65
double-deficient background. We found that K430R-Btk expression rescued
the severe developmental arrest at the pre-B-cell stage in Btk/SLP-65
double-deficient mice. Moreover, K430R-Btk co
Bruton's Tyrosine Kinase Cooperates with the B Cell Linker Protein SLP-65 as a Tumor Suppressor in Pre-B Cells
Expression of the pre-B cell receptor (pre-BCR) leads to activation of the adaptor molecule SLP-65 and the cytoplasmic kinase Btk. Mice deficient for one of these signaling proteins have an incomplete block in B cell development at the stage of large cycling pre-BCR+CD43+ pre-B cells. Our recent findings of defective SLP-65 expression in ∼50% of childhood pre-B acute lymphoblastic leukemias and spontaneous pre-B cell lymphoma development in SLP-65−/− mice demonstrate that SLP-65 acts as a tumor suppressor. To investigate cooperation between Btk and SLP-65, we characterized the pre-B cell compartment in single and double mutant mice, and found that the two proteins have a synergistic role in the developmental progression of large cycling into small resting pre-B cells. We show that Btk/SLP-65 double mutant mice have a dramatically increased pre-B cell tumor incidence (∼75% at 16 wk of age), as compared with SLP-65 single deficient mice (<10%). These findings demonstrate that Btk cooperates with SLP-65 as a tumor suppressor in pre-B cells. Furthermore, transgenic low-level expression of a constitutive active form of Btk, the E41K-Y223F mutant, prevented tumor formation in Btk/SLP-65 double mutant mice, indicating that constitutive active Btk can substitute for SLP-65 as a tumor suppressor
Ray chaos in optical cavities based upon standard laser mirrors
We present a composite optical cavity made of standard laser mirrors; the
cavity consists of a suitable combination of stable and unstable cavities. In
spite of its very open nature the composite cavity shows ray chaos, which may
be either soft or hard, depending on the cavity configuration. This opens a
new, convenient route for experimental studies of the quantum aspects of a
chaotic wave field.Comment: 4 pages, 3 figures, 1 tabl
Generation of pulsed and continuous-wave squeezed light with Rb vapor
We present experimental studies on the generation of pulsed and
continuous-wave squeezed vacuum via nonlinear rotation of the polarization
ellipse in a Rb vapor. Squeezing is observed for a wide range of input
powers and pump detunings on the D1 line, while only excess noise is present on
the D2 line. The maximum continuous-wave squeezing observed is -
dB (-2.0 dB corrected for losses). We measure -1.1 dB squeezing at the
resonance frequency of the Rb transition, which may allow
the storage of squeezed light generated by Rb in a Rb quantum
memory. Using a pulsed pump, pulsed squeezed light with -1 dB of squeezing for
200 ns pulse widths is observed at 1 MHz repetition rate.Comment: 9 pages, 5 figure
Experimental observation of wave chaos in a conventional optical resonator
Quantum Matter and Optic
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