Generation of a CLTA reporter human induced pluripotent stem cell line, CRMi001-A-1, using the CRISPR/Cas9 system to monitor endogenous clathrin trafficking

The most highly studied endocytic pathway, clathrin-dependent endocytosis, mediates a wide range of fundamental processes including nutrient internalization, receptor recycling, and signal transduction. In order to model tissue specific and developmental aspects of this process, CRISPR/Cas9 genomic editing was utilized to fluorescently label the C-terminus of clathrin light chain A (CLTA) within the phenotypically normal, parental CRMi001-A human induced pluripotent stem cell line. Successfully edited cells were isolated by fluorescently activated cell sorting, remained karyotypically normal, and maintained their differentiation potential. This cell line facilitates imaging of endogenous clathrin trafficking within varied cell types

Human HLA-DR Transgenes Protect Mice from Fatal Virus-Induced Encephalomyelitis and Chronic Demyelination▿

We evaluated the participatory role of human HLA-DR molecules in control of virus from the central nervous system and in the development of subsequent spinal cord demyelination. The experiments utilized intracranial infection with Theiler's murine encephalomyelitis virus (TMEV), a picornavirus that, in some strains of mice, results in primary demyelination. We studied DR2 and DR3 transgenic mice that were bred onto a combined class I-deficient mouse (beta-2 microglobulin deficient; β2m0) and class II-deficient mouse (Aβ0) of the H-2b background. Aβ0.β2m0 mice infected with TMEV died within 18 days of infection. These mice showed severe encephalomyelitis due to rapid replication of virus genome. In contrast, transgenic mice with insertion of a single human class II major histocompatibility complex (MHC) gene (DR2 or DR3) survived the acute infection. DR2 and DR3 mice controlled virus infection by 45 days and did not develop spinal cord demyelination. Levels of virus RNA were reduced in HLA-DR transgenic mice compared to Aβ0.β2m0 mice. Virus-neutralizing antibody responses did not explain why DR mice survived the infection and controlled virus replication. However, DR mice showed an increase in gamma interferon and interleukin-2 transcripts in the brain, which were associated with protection. The findings support the hypothesis that the expression of a single human class II MHC molecule can, by itself, influence the control of an intracerebral pathogen in a host without a competent class I MHC immune response. The mechanism of protection appears to be the result of cytokines released by CD4+ T cells

Consequences of TCDD Treatment on Intra-Hepatic Lymphocytes During Liver Regeneration

Increasing evidence demonstrates a physiological role for the aryl hydrocarbon receptor (AhR) in regulating hepatocyte cell cycle progression. Previous studies have used a murine model of liver regeneration to show that exposure to the potent exogenous AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), suppresses hepatocyte proliferation in vivo. Based on recent reports that natural killer (NK) cells negatively regulate liver regeneration, coupled with the well-established immunomodulatory effects of TCDD, it was hypothesized that alterations in lymphocyte activation contribute to the suppression of liver regeneration in TCDD-treated mice. To test this, mice were treated with TCDD (20 μg/kg) 1 day prior to 70% partial hepatectomy (PH), in which two-thirds of the liver was surgically resected. Lymphocytes were collected from the remnant liver and analyzed by flow cytometry. Whereas exposure to TCDD did not alter the number of NK cells or CD3+ T-cells recovered from the regenerating liver, it reduced the percentage and number of intra-hepatic NKT cells 42 h after PH. With regard to lymphocyte activation, TCDD treatment transiently increased CD69 expression on NK and NKT cells 12 h after PH, but had no effect on intracellular levels of IFNγ in NK, NKT, or CD3+ T-cells. To determine the relevance of NK cells to the suppression of liver regeneration by TCDD, mice were treated with anti-Asialo GM-1 (ASGM-1) antibody to deplete NK cells prior to TCDD treatment and PH, and hepatocyte proliferation was measured using bromodeoxyuridine incorporation. Exposure to TCDD was found to inhibit hepatocyte proliferation in the regenerating liver of NK cell-depleted mice and control mice to the same extent. Hence, it is unlikely that enhanced numbers or increased activation of NK cells contribute to the suppression of liver regeneration in TCDD-treated mice