sible for regulating the shift in chondrocyte gene expression profile to a catabolic phenotype by increasing transcripts of specific matrix metallopro- teinases (MMP), including MMP-9 and MMP-12 and decreasing transcripts of selective cartilage matrix genes, including Col2a1, Hapln1 and Agc1. We determined that the activity of downstream transcription factor targets of TNF- α signaling, including NF-κB and Sox9, were independent of MEK1/2 activity. Promoter analysis of the rat Col2a1 and Agc1 genes identified overlapping Sp1/ Egr-1 binding sites. Egr-1 DNA binding, but not nuclear localization was increased by TNF-α in a MEK1/2-dependent manner. Inhibition of TNF-α- induced Egr-1 genomic DNA binding by oligonucleotide decoy determined that Egr-1 is a primary regulator of Col2a1, Hapln1 and Agc1. Thus, Egr-1 activation is required to initiate at least part of the changes in chondrocyte gene expression in response to TNF-α-activated MEK/ERK. Breakdown of TNF-α signaling into its component pathways may uncover new therapeutic targets, such as Egr-1, for treatmentof destructive joint disorders. doi:10.1016/j.matbio.2008.09.259 45 The protein arginine methyltransferase (PRMT5) associates with class II transactivator (CIITA) to repress collagen transcription Larry Luchsinger, B.D. Smith Department of Biochemistry, Boston University School of Medicine, Boston, MA, 02118, United States Wound healing proceeds through a series of overlapping, highly regulated stages with complex interplay of cells, extracellular matrix and soluble mediators to regenerate and remodel tissue. Investigation of collagen synthesis in wound healing has centered on repair, rather than inflammation. We have are characterizing the transcription factors responsible for up-regulation of immunity, which act by inducing major histocompatibility class II (MHC II) while simultaneously down-regulating collagen synthesis. Our published studies on the inflammatory cytokine interferon gamma (IFN) demonstrate that IFN increases expression of regulatory factor for X box 5 (RFX5) and class II transactivator (CIITA) to assemble a co-repressor complex at the collagen promoter. Our studies indicate that CIITA interacts with previously identified co- repressors (Sin3B and HDAC2) in a phosphorylation dependent manner through its proline/serine/threonine (PST) domain. However, the complete repertoire of molecules that aid CIITA in silencing collagen transcription remains unknown. MALDI-TOF mass spectrometry identified a novel protein, protein arginine methyltransferase (PRMT5), that associates with the PST-domain in co- immunoprecipitation experiments. Interaction of PRMT5 with CIITA was confirmed by reciprocal co-immunoprecipitation of CIITA with FLAG-PRMT5. Methylation assays show that the immunoprecipitates contain methyl transfer- ase activity. PRMT5 has been shown to preferentially symmetrically dimethy- lates histone arginine residues, H4R3 as well as H3R8, which places it in the rapidly expanding class of chromatin modifying proteins. The role of histone methylation by PRMT5 in gene expression remains elusive. Transfection of PRMT5 with collagen promoters indicates that PRMT5 represses collagen transcription; particularly in the presence of CIITA. Examination of the function of PRMT5 methylation on the collagen locus may lead to further insight into chromatin modification and its contribution in collagen repression. doi:10.1016/j.matbio.2008.09.260 46 Modulation of cell adhesion and migration by Bcl-2 Christine M. Sorenson, Nader Sheibani University of Wisconsin School of Medicine and Public Health, United States Bcl-2 is the founding member of a family of proteins that regulate apoptosis. During kidney development bcl-2 not only acts as a survival factor but also impacts cell adhesive mechanisms, perhaps through modulation of the composition of the extracellular matrix (ECM) milieu. Our hypothesis is that bcl-2 regulates renal development through modulation of the composi- tion of the extracellular microenvironment impacting cell adhesion, migra- tion, and apoptosis processes. Here we examined the effect lack of bcl-2 has on adhesion, migration, and apoptosis of ureteric bud (UB) and their matured progeny collecting duct (CD) cells, and whether alterations in production of ECM proteins occurs in the absence of bcl-2. In the normal kidney, production of ECM proteins is developmentally regulated. Significant expression of thromobospondin-1 (TSP1) and osteopontin is observed in bcl-2 +/+ UB cells, and later in postnatal day 10 (P10) CD cells. Following renal maturation, the expression of these proteins is significantly down-regulated. Fibronectin expression remains at a modest level throughout kidney development in bcl-2 +/+ cells. In contrast, bcl-2-/- UB cells and P10 CD cells demonstrated precocious down-regulation of TSP1 and osteopontin. The bcl-2-/- cells also exhibited increased fibronectin expression, increased cell migration, and decreased adhesion to vitronectin and fibronectin compared to bcl-2 +/+ cells. Bcl-2 +/+ UB and collecting duct cells readily branched in Matrigel and collagen gel, while bcl-2-/- cells did not undergo significant branching in either matrix protein. Taken together, these data suggest that bcl-2 expression significantly impacts cell adhesive and migratory mechanisms through modulation of ECM composition such that in its absence, branching morphogenesis is compromised both in vitro and in vivo. doi:10.1016/j.matbio.2008.09.261 47 Integrin-laminin interaction in kidney papillae development Tetyana L. Vasylyeva a , Qin Shan a , Yingjie Liu a , Charles Szekeres a , Mary Taglienti a , Jeffrey H. Miner b , Jordan A. Kreidberg a a Department of Medicine, Division of Nephrology, Children's Hospital Boston, Harvard Medical School, Boston, MA, United States b Renal Division, Washington University School of Medicine, St. Louis, MO, United States Integrins, as receptors for the extracellular matrix, play a significant role in kidney development. Mice deficient in α 3β1 integrin have abnormal glomeruli due to podocyte damage, and do not survive beyond the birth. The focus of this study was to investigate the role of α3 β 1 integrin in the development of the kidney collecting system. Branching and elongation events were assessed in early kidney morphogenesis in α3 integrin null (KO) and wild type (WT) embryos. An α3 integrin conditional allele was crossed with HoxB7-cre transgenic mice to study postnatal kidney development. To study a role of integrin-laminin(L) interaction, Lama5 transgenic mice were created by knocking out the α subunit in L10, using Pax2Cre in Lama5-flox/ null animals. Studies included morphometric analysis, immunohistochem- istry for Ki67, TUNEL assay, immunofluorescent staining and measurement of proteinurea. Both tubular elongation and branching were affected by a loss of α3 β 1 integrin or laminin. The difference in elongation became obvious in experimental embryonic kidneys by E18.5. Ki67 staining showed that the cKO had fewer proliferating cells in the tubular structures than did WT. cKO also had a higher number of apoptotic figures. We conclude that mice with deformed papillae can survive until adulthood under non-stress conditions. α 3β 1 integrin and L10 are important for normal development of collecting tubules, and play a significant role in tubular elongation and branching. doi:10.1016/j.matbio.2008.09.262 48 Matrilin-1 in the vertebral column of salmon with deformities Mona E. Pedersen a , Eva Veiseth a , Harald Takle b , Elisabeth Ytteborg b , Grete Baeverfjord c , Grethe Enersen a , Kirsten O. Hannesson a a Nofima Food Matforsk AS, N1430 Ås, Norway b Nofima Marine, N1432 Ås, Norway c Nofima Marine, N6600 Sunndalsøra, Norway Skeletal formation and growth in fish species as Atlantic salmon include intramembranous bone formation and perichondral/periostal ossification in Abstracts S20