A major transcription factor involved is Mitf that contains both basic helix-loop-helix and leucine zipper structural features. chymase activity may DC661 be responsible for some unique phenotypes observed in DBA/2 mice. == Introduction == Mast cells are innate immune cells best known for their involvement in anaphylaxis, atopic asthma and other IgE-associated allergic disorders[1]. They DC661 also carry out a number of beneficial functions to the host including immune responses toward various pathogens. They are derived from hematopoietic stem cells and are widely distributed in tissues. Mast cells express a number of proteases including chymase, tryptase, and carboxypeptidaseA[2]. In mice, Mcp-1, -2, -4, -5, -9, and -10 are designated as chymases based on deduced amino acid sequences, whereas Mcp-6 and -7 are tryptases. These enzymes are stored in high amounts as active enzymes in mast cell secretory granules. Upon activation, massive fully active mast cell proteases are released through mast cell degranulation and elicit essential impacts on many physiological and pathological events which include extracellular matrix remodeling, extravascular coagulation, fibrinolysis, angiogenesis as well as antibacterial inflammatory responses[3]. Expressions of chymases are strictly regulated. At the level of transcriptional regulation, a well-documented transcription factor is Mitf. Direct or indirect binding of Mitf to the promoter element CANNTG can significantly enhance the expression of Mcp-2, -4, -5, -6, and -9 genes in C57BL/6 mice[4]. In addition to Mitf, bifunctional transcription factors C/EBP and YY1 are thought to be responsible for the negative transcriptional regulation of Mcp-2 via intracellularly retained IL-15[5],[6]. In wild type bone marrow-derived mast cells (BMMCs), C/EBP is preferentially expressed over YY1 and binds to the Mcp-2 promoter. Rabbit Polyclonal to 5-HT-2B In contrast, in IL-15-deficient BMMCs, YY1 is dominantly expressed and binds to the Mcp-2 promoter, which allows hyper-transcription of the Mcp-2 gene[5]. Expression of chymases in mast cells is also known to be controlled at the post-transcriptional level. For example, an earlier study demonstrated that the half-life of the Mcp-2 transcript in mouse BMMCs was extended by 4-fold in the presence of IL-10[7]. Together, expressions of chymases are regulated at multiple levels. We previously generated a line of JAK2V617F transgenic mice that display polycythemia vera-like phenotypes[8]. Our most recent work demonstrated that the occurrence of PV-associated pruritus in these mice was associated with elevated levels of mast cells (Jin et al, unpublished). In this DC661 study, we DC661 identified a subpopulation of JAK2V617F transgenic mice that express very high levels of Mcp-2 and Mcp-4 in mast cells. However, this was found to be independent of JAK2V617F and due instead to the presence of Mcp-2 and Mcp-4 gene variants originated from DBA/2 mice. Our study thus provides a new line of congenic C57BL/6 mice with high expressions of specific chymases in mast cells. == Materials and Methods == == Mice == JAK2V617F transgenic mice were generated with a C57BL/6DBA/2 hybrid background and then crossed with wild type C57BL/6 mice for over 10 generations[8]. Wild-type C57BL/6 and DBA/2 mice were purchased from The Jackson Laboratory. Animals were housed in ventilated cages under standard conditions. This study was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by the Institutional Animal Care and Use Committee of the University of Oklahoma Health Sciences Center. == Culture of Mast Cells == Bone marrow and peritoneal cavity cells from mice were cultured in Iscoves modified Dulbeccos medium (IMDM) supplemented with 20% fetal bovine serum (FBS) and 1% each of conditioned media of cultured CHO cells overexpressing mIL-3 and DC661 mSCF. The resultant mast cells were analyzed after one month of culture initiation and maintained for up to four months with equal volumes of fresh medium added every 3 to 5 5 days. These cells were >95% pure based on positive staining for CD117 (c-Kit) and FcR1 upon flow cytometric analyses. == Proteomic Analyses == Protein identification was carried out by using the Mass Spectrometry and Proteomics core facility at the University of Oklahoma Health Sciences Center. In brief, proteins were separated on SDS gels, and protein bands were excised for digestion with trypsin..