Advantages of this platform include the application of versatile cell assays to quantitative (residual) munc13-4 function, and to rank severity of FHL3 mutations. It also offers the possibility to test small molecular weight compounds for their ability to restore secretory lysosome degranulation in FHL3. Antibodies were obtained from the indicated sources: p80 mouse hybridoma 5G10 (J. Bonifacino, NIH Bethesda), mouse anti serotonin (DAKO), mouse anti rat CD63 (BD Biosciences), mouse IgE anti DNP clone SPE-7 and corresponding

antigen Selleck Target Selective Inhibitor Library HSA-DNP (Sigma), mouse anti GFP (Roche), conjugated secondary antibodies (Jackson Immuno Research Laboratories). The rabbit antibody against munc13-4 has been described (Neeft et al., 2005). Following plasmids were generously provided by indicated

colleagues: peYFP-N1-Munc13-4 Forskolin solubility dmso cDNA (V.Gerke, ZMBE Münster), pLNT-SFFV-WPRE-Gateway (G. Griffiths, CIMR Cambridge), lentiviral helper plasmids psPAX2 and pMD2.G (A. Mertens UMC Utrecht). cDNAs encoding human munc13-4 and munc13-4-Δ608-611 were generated previously in this lab (Neeft et al., 2005). The RBL-2H3 cell line was generously provided by Ronit Sagi Eisenberg (Tel Aviv University) and cloned by limited dilution to obtain clones in which β-hexosaminidase secretion could be stimulated to yield at least 30% release. The cells were cultured in DMEM containing 1 mg ml−1 glucose, 10% heat-inactivated FCS (Bodinco), 100 U ml−1 penicillin, 100 μg ml−1 streptomycin, 2 mM l-glutamine, 50 nM 2-mercaptoethanol and passaged 3 times a week 1/20. Degranulation of RBL-2H3 cells is influenced by FCS and care was taken Immune system to obtain a batch that did not affect degranulation. HEK293T were cultured in DMEM (Invitrogen) 5 mg ml−1 glucose, 10% heat-inactivated fetal calf serum (Sigma), 100 U ml−1

penicillin, 100 μg ml−1 streptomycin and 2 mM l-glutamine. YFP-tagged munc13-4 cDNAs were extended with attB sites for cloning in pDONr201 (Invitrogen). After amplification inserts were transferred to the lentiviral plasmid pLNT–SFFV–WPRE–Gateway (Demaison et al., 2002) using LR Clonase II (Invitrogen). This lentiviral plasmid was developed to induce gene expression in hematopoietic cells using a spleen focus forming virus (SFFV) promoter, Woodchuck hepatitis virus posttranscriptional regulatory element (WPRE), central polypurine tract (cPPT) and appended with a gateway cloning cassette between the long terminal repeats (LTR). Primers GGGGACAAGTTTGTACAAAAAAGCAGGCTTCATGGTGAGCAAGGGCGAGGAGCTG (f), GGGGACCACTTTGTACAAGAAAGCTGGGTCCTACGGTGCCGGCCGCAAGGC (r) were used for YFP on the N-terminus, and GGGGACAAGTTTGTACAAAAAAGCA GGC TTCATGGCGA CACTCCTCTCCCATCC (f), and GGGGACCACTTTGTACAAG AAAGCTGGGTCTTACTTGTACAGCTCGTCCATGC for YFP at the C-terminus. All constructs obtained through PCR were verified by sequencing. VSV-G pseudotyped lentivirus was prepared in low passage number HEK293T cells.