Stat3 Signaling Promotes Survival And Maintenance Of Medullary Thymic Epithelial Cells

Medullary thymic epithelial cells (mTECs) are essential for establishing central tolerance by expressing a diverse array of self-peptides that delete autoreactive thymocytes and/or divert thymocytes into the regulatory T cell lineage. Activation of the NFκB signaling pathway in mTEC precursors is indispensable for mTEC maturation and proliferation resulting in proper medullary region formation. Here we show that the Stat3-mediated signaling pathway also plays a key role in mTEC development and homeostasis. Expression of a constitutively active Stat3 transgene targeted to the mTEC compartment increases mTEC cellularity and bypasses the requirement for signals from positively selected thymocytes to drive medullary region formation. Conversely, conditional deletion of Stat3 disrupts medullary region architecture and reduces the number of mTECs. Stat3 signaling does not affect mTEC proliferation, but rather promotes survival of immature MHCII^loCD80^lo mTEC precursors. In contrast to striking alterations in the mTEC compartment, neither enforced expression nor deletion of Stat3 affects cTEC cellularity or organization. These results demonstrate that in addition to the NFkB pathway, Stat3-mediated signals play an essential role in regulating mTEC cellularity and medullary region homeostasis.     

Invariant TAD Boundaries Constrain Cell-Type-Specific Looping Interactions between Promoters and Distal Elements around the CFTR Locus

Three-dimensional genome structure plays an important role in gene regulation. Globally, chromosomes are organized into active and inactive compartments while, at the gene level, looping interactions connect promoters to regulatory elements. Topologically associating domains (TADs), typically several hundred kilobases in size, form an intermediate level of organization. Major questions include how TADs are formed and how they are related to looping interactions between genes and regulatory elements. Here we performed a focused 5C analysis of a 2.8 Mb chromosome 7 region surrounding CFTR in a panel of cell types. We find that the same TAD boundaries are present in all cell types, indicating that TADs represent a universal chromosome architecture. Furthermore, we find that these TAD boundaries are present irrespective of the expression and looping of genes located between them. In contrast, looping interactions between promoters and regulatory elements are cell-type specific and occur mostly within TADs. This is exemplified by the CFTR promoter that in different cell types interacts with distinct sets of distal cell-type-specific regulatory elements that are all located within the same TAD. Finally, we find that long-range associations between loci located in different TADs are also detected, but these display much lower interaction frequencies than looping interactions within TADs. Interestingly, interactions between TADs are also highly cell-type-specific and often involve loci clustered around TAD boundaries. These data point to key roles of invariant TAD boundaries in constraining as well as mediating cell-type-specific long-range interactions and gene regulation.     

Aptamer-graphene oxide for highly sensitive dual electrochemical detection of Plasmodium lactate dehydrogenase

A 90 mer ssDNA aptamer (P38) enriched against Plasmodium falciparum lactate dehydrogenase (PfLDH) through SELEX process was immobilized over glassy carbon electrode (GCE) using graphene oxide (GO) as an immobilization matrix, and the modified electrode was investigated for detection of PfLDH. The GO was synthesized from powdered pencil graphite and characterized by XRD based on the increased interlayer distance between graphitic layers from 0.345 nm for graphite to 0.829 nm for GO. The immobilization of P38 on GO was confirmed by I_D/I_G intensity ratio in Raman spectra where, the ratio were 0.67, 0.915, and 1.35 for graphite, GO and P38-GO, respectively. The formation of the P38 layer over GO-GCE was evident from an increase in the surface height in AFM analysis of the electrode from ∼3.5 nm for GO-GCE to ∼27 nm for P38-GO-GCE. The developed aptasensor when challenged with the target, a detection of as low as 0.5 fM of PfLDH was demonstrated. The specificity of the aptasensor was confirmed through a voltametric measurement at 0.65 V of the reduced co-factor generated from the PfLDH catalysis. Studies on interference from some common proteins, storage stability, repeatability and analysis of real samples demonstrated the practical application potential of the aptasensor.     

Antibacterial effect of bestatin during periodontitis

Periodontitis is a polymicrobial disease inciting inflammatory destruction of the tooth-supporting tissues, i.e., periodontium. The initiation of this infectious disease is ascribed to the formation of subgingival biofilms. These biofilms cause stimulation of myriad of chronic inflammatory reactions by the affected tissue. The Gram-negative anaerobe Porphyromonas gingivalis is commonly found as part of the microbiota of subgingival biofilms, and is involved in the occurrence of the disease. P. gingivalis possesses numerous virulence factors supporting its survival, regulating its communication with other species in the biofilm, degrading host tissues. Fusobacterium nucleatum is pivotal for formation of biofilm and promotes growth and invasion properties of P. gingivalis. Bestatin is an aminopeptide inhibitor, produced by actinomycetes. It possesses antibacterial properties against P. gingivalis and F. nucleatum. The following review focuses on action of bestatin on the mentioned bacteria.