Differential Requirement of Cd8 Enhancers E8I and E8VI in Cytotoxic Lineage T Cells and in Intestinal Intraepithelial Lymphocytes

CD8 expression in T lymphocytes is tightly regulated by the activity of at least six Cd8 enhancers (E8I-E8VI), however their complex developmental stage-, subset-, and lineage-specific interplays are incompletely understood. Here we analyzed ATAC-seq data on the Immunological Genome Project database and identified a similar developmental regulation of chromatin accessibility of a subregion of E8I, designated E8I-core, and of E8VI. Loss of E8I-core led to a similar reduction in CD8 expression in naïve CD8+ T cells and in IELs as observed in E8I−/− mice, demonstrating that we identified the core enhancer region of E8I. While E8VI−/− mice displayed a mild reduction in CD8 expression levels on CD8SP thymocytes and peripheral CD8+ T cells, CD8 levels were further reduced upon combined deletion of E8I-core and E8VI. Moreover, activated E8I-core−/−E8VI−/− CD8+ T cells lost CD8 expression to a greater degree than E8I-core−/− and E8VI−/− CD8+ T cells, suggesting that the combined activity of both enhancers is required for establishment and maintenance of CD8 expression before and after TCR activation. Finally, we observed a severe reduction of CD4 CTLs among the TCRβ+CD4+ IEL population in E8I-core−/− but not E8VI−/− mice. Such a reduction was not observed in Cd8a−/− mice, indicating that E8I-core controls the generation of CD4 CTLs independently of its role in Cd8a gene regulation. Further, the combined deletion of E8I-core and E8VI restored CD4 CTL subsets, suggesting an antagonistic function of E8VI in the generation of CD4 CTLs. Together, our study demonstrates a complex utilization and interplay of E8I-core and E8VI in regulating CD8 expression in cytotoxic lineage T cells and in IELs. Moreover, we revealed a novel E8I-mediated regulatory mechanism controlling the generation of intestinal CD4 CTLs

The corepressor NCOR1 regulates the survival of single-positive thymocytes

Nuclear receptor corepressor 1 (NCOR1) is a transcriptional regulator bridging repressive chromatin modifying enzymes with transcription factors. NCOR1 regulates many biological processes, however its role in T cells is not known. Here we show that Cd4-Cre-mediated deletion of NCOR1 (NCOR1 cKOCd4) resulted in a reduction of peripheral T cell numbers due to a decrease in single-positive (SP) thymocytes. In contrast, double-positive (DP) thymocyte numbers were not affected in the absence of NCOR1. The reduction in SP cells was due to diminished survival of NCOR1-null postselection TCRhiCD69+ and mature TCRhiCD69 thymocytes. NCOR1-null thymocytes expressed elevated levels of the pro-apoptotic factor BIM and showed a higher fraction of cleaved caspase 3-positive cells upon TCR stimulation ex vivo. However, staphylococcal enterotoxin B (SEB)-mediated deletion of V8+ CD4SP thymocytes was normal, suggesting that negative selection is not altered in the absence of NCOR1. Finally, transgenic expression of the pro-survival protein BCL2 restored the population of CD69+ thymocytes in NCOR1 cKOCd4 mice to a similar percentage as observed in WT mice. Together, these data identify NCOR1 as a crucial regulator of the survival of SP thymocytes and revealed that NCOR1 is essential for the proper generation of the peripheral T cell pool.(VLID)463721

Correction: Alterations of Red Cell Membrane Properties in Neuroacanthocytosis.

Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an “acanthocytic state” of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration

RMH-1 promotes the bias for CO formation on chromosome arms.

<p>(A) Schematics of crosses to obtain the progeny of singled F2 individuals subjected to Next Generation Sequencing (NGS) for SNP analysis. White insert indicates the WT (Bristol) background, and black insert indicates the Hawaiian background. (B) Quantification of the overall recombination frequencies for assayed chromosomes; stacked bar graph indicates the fraction of meiotic products with zero, one, or two COs. For WT (<i>n</i> = 36 chromatids), for <i>rmh-1(jf54)</i> (<i>n</i> = 40 chromatids), and for <i>rmh-1(tn309)</i> (<i>n</i> = 45 chromatids). The frequency of COs was not found to be different between WT and both mutants (Chi² test). (C) Scheme of the different chromosomes used during the recombination assay. The chromosome domains (left arm in blue, center in yellow, and right arm in purple) are correlated with the physical map of each chromosome. (D) Locations of the recombination events (assayed for chromosomes X, IV, and V) in WT (<i>n</i> = 17 COs: three events on X, four on II, four on IV, and six on V), for <i>rmh-1(jf54)</i> (<i>n</i> = 20 COs: 11 events on II and 9 on V), and <i>rmh-1(tn309)</i> (<i>n</i> = 21 COs: nine events on X, nine on IV, and three on V); also see the <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002412#sec015" target="_blank">Experimental Procedures</a> section. The relative distribution of COs in the center versus arm domains differed from the WT for <i>tn309</i> (<i>p</i> = 0.046, Chi² test) and for <i>jf54</i>, (p = 0.062, Chi² test).</p