HLA-DR15 Molecules Jointly Shape an Autoreactive T Cell Repertoire in Multiple Sclerosis.

The HLA-DR15 haplotype is the strongest genetic risk factor for multiple sclerosis (MS), but our understanding of how it contributes to MS is limited. Because autoreactive CD4+ T cells and B cells as antigen-presenting cells are involved in MS pathogenesis, we characterized the immunopeptidomes of the two HLA-DR15 allomorphs DR2a and DR2b of human primary B cells and monocytes, thymus, and MS brain tissue. Self-peptides from HLA-DR molecules, particularly from DR2a and DR2b themselves, are abundant on B cells and thymic antigen-presenting cells. Furthermore, we identified autoreactive CD4+ T cell clones that can cross-react with HLA-DR-derived self-peptides (HLA-DR-SPs), peptides from MS-associated foreign agents (Epstein-Barr virus and Akkermansia muciniphila), and autoantigens presented by DR2a and DR2b. Thus, both HLA-DR15 allomorphs jointly shape an autoreactive T cell repertoire by serving as antigen-presenting structures and epitope sources and by presenting the same foreign peptides and autoantigens to autoreactive CD4+ T cells in MS.

Nf1 deletion results in depletion of the Lhx6 transcription factor and a specific loss of parvalbumin+ cortical interneurons.

Neurofibromatosis 1 (NF1) is caused by mutations in the NF1 gene, which encodes the protein, neurofibromin, an inhibitor of Ras activity. Cortical GABAergic interneurons (CINs) are implicated in NF1 pathology, but the cellular and molecular changes to CINs are unknown. We deleted mouse Nf1 from the medial ganglionic eminence, which gives rise to both oligodendrocytes and CINs that express somatostatin and parvalbumin. Nf1 loss led to a persistence of immature oligodendrocytes that prevented later-generated oligodendrocytes from occupying the cortex. Moreover, molecular and cellular properties of parvalbumin (PV)-positive CINs were altered by the loss of Nf1, without changes in somatostatin (SST)-positive CINs. We discovered that loss of Nf1 results in a dose-dependent decrease in Lhx6 expression, the transcription factor necessary to establish SST+ and PV+ CINs, which was rescued by the MEK inhibitor SL327, revealing a mechanism whereby a neurofibromin/Ras/MEK pathway regulates a critical CIN developmental milestone.

Galectin-1 binds different CD43 glycoforms to cluster CD43 and regulate T cell death.

Galectin-1 kills immature thymocytes and activated peripheral T cells by binding to glycans on T cell glycoproteins including CD7, CD45, and CD43. Although roles for CD7 and CD45 in regulating galectin-1-induced death have been described, the requirement for CD43 remains unknown. We describe a novel role for CD43 in galectin-1-induced death, and the effects of O-glycan modification on galectin-1 binding to CD43. Loss of CD43 expression reduced galectin-1 death of murine thymocytes and human T lymphoblastoid cells, indicating that CD43 is required for maximal T cell susceptibility to galectin-1. CD43, which is heavily O-glycosylated, contributes a significant fraction of galectin-1 binding sites on T cells, as T cells lacking CD43 bound approximately 50% less galectin-1 than T cells expressing CD43. Although core 2 modification of O-glycans on other glycoprotein receptors is critical for galectin-1-induced cross-linking and T cell death, galectin-1 bound to CD43 fusion proteins modified with either unbranched core 1 or branched core 2 O-glycans and expression of core 2 O-glycans did not enhance galectin-1 binding to CD43 on T cells. Moreover, galectin-1 binding clustered CD43 modified with either core 1 or core 2 O-glycans on the T cell surface. Thus, CD43 bearing either core 1 or core 2 O-glycans can positively regulate T cell susceptibility to galectin-1, identifying a novel function for CD43 in controlling cell death. In addition, these studies demonstrate that different T cell glycoproteins on the same cell have distinct requirements for glycan modifications that allow recognition and cross-linking by galectin-1.

Real-time quantification of microRNAs by stem-loop RT-PCR.

A novel microRNA (miRNA) quantification method has been developed using stem-loop RT followed by TaqMan PCR analysis. Stem-loop RT primers are better than conventional ones in terms of RT efficiency and specificity. TaqMan miRNA assays are specific for mature miRNAs and discriminate among related miRNAs that differ by as little as one nucleotide. Furthermore, they are not affected by genomic DNA contamination. Precise quantification is achieved routinely with as little as 25 pg of total RNA for most miRNAs. In fact, the high sensitivity, specificity and precision of this method allows for direct analysis of a single cell without nucleic acid purification. Like standard TaqMan gene expression assays, TaqMan miRNA assays exhibit a dynamic range of seven orders of magnitude. Quantification of five miRNAs in seven mouse tissues showed variation from less than 10 to more than 30,000 copies per cell. This method enables fast, accurate and sensitive miRNA expression profiling and can identify and monitor potential biomarkers specific to tissues or diseases. Stem-loop RT-PCR can be used for the quantification of other small RNA molecules such as short interfering RNAs (siRNAs). Furthermore, the concept of stem-loop RT primer design could be applied in small RNA cloning and multiplex assays for better specificity and efficiency.

Potential role for mitogen-activated protein kinase phosphatase-1 in the development of atherosclerotic lesions in mouse models.

OBJECTIVE: Mitogen-activated protein kinase phosphatase-1 (MKP-1) is one of several oxidized-l-alpha-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (Ox-PAPC)-induced genes identified in human aortic endothelial cells (HAEC). We previously reported that MKP-1 activity is required for Ox-PAPC-mediated endothelial/monocyte interactions; however, an in vivo role of MKP-1 in atherogenesis has not been investigated. METHODS AND RESULTS: We now report that MKP-1 protein is expressed in the atherosclerotic lesions of mice. MKP-1 mRNA expression is highly induced in C57BL6/J mice on an atherogenic diet, low-density lipoprotein receptor (LDLR) (-/-) mice on a Western diet, and 10-week or older ApoE (-/-) mice on a chow diet. In ApoE (-/-) mice treated with 1 mg/mL of sodium orthovanadate (NaOV), a specific inhibitor of tyrosine phosphatases including MKP-1, total phosphatase activity and MKP-1 protein were decreased in both the aortic lesions and liver lysates. In 3 animal models of atherosclerosis [C57BL6/J mice on an atherogenic diet for 15 weeks, LDLR (-/-) mice on a Western diet for 10 weeks, and ApoE (-/-) mice on a chow diet for 8 weeks], mice treated with NaOV had significantly smaller atherosclerotic lesions when compared with the control group. CONCLUSIONS: MKP-1 expression is associated with hypercholesterolemia and atherosclerosis, and inhibition of MKP-1 activity may prevent atherosclerotic lesion development in mice. MKP-1 is required for Ox-PAPC-mediated endothelial/monocyte interactions; however, an in vivo role of MKP-1 in atherogenesis has not been investigated. We now report that MKP-1 protein is expressed in the atherosclerotic lesions of mice and inhibition of tyrosine phosphatase activity and MKP-1 protein reduce atherosclerotic lesions in mouse models.

Repetitive, noninvasive imaging of cyclooxygenase-2 gene expression in living mice.

The cyclooxygenase-2 (COX-2) gene plays a role in a wide variety of normal physiologic pathways and is a major target of pharmacologic intervention in a large number of pathophysiologic contexts, including pain, fever, inflammation, and cancer. Expression of the COX-2 gene is induced in a wide range of cells, in response to an ever-increasing number of stimuli. The regulation of the COX-2 gene has been the subject of extensive study, using traditional transfection techniques with reporter gene constructs. Regulation of the COX-2 gene in living animals, however, requires sacrifice of the animal and in situ hybridization and/or immunohistochemical studies. We have utilized in vivo optical imaging technology with a cooled charged coupled device camera to image the expression of the firefly luciferase gene in tumor xenografts that are stably transfected with a chimeric gene containing the first kilobase of the murine COX-2 promoter. Induction of luciferase gene expression following systemic lipopolysaccharide/endotoxin administration can be robustly demonstrated; both a dose-response relationship and a time course for luciferase expression from the COX-2 promoter can be noninvasively analyzed in the tumor xenografts. These data suggest expression from the COX-2 promoter will be easily analyzed in transgenic mice, in knock-in mice, and in somatic cell and gene transfer experiments.