Xpression level of other sec1/munc18 family members, STXBP1+/+ and 1379592 STXBP12/2 LMCs were sensitized with anti-TNP IgE overnight and stimulated with TNP-BSA for 90 minutes or left untreated (NT). Gene expression was analyzed by RT-PCR using mRNA isolated from these cells. As expected, expression of the STXBP1 gene in STXBP12/2 LMC was not detected, while the expression of other members of the SM family were unimpaired (Fig. 1E). Indeed, all SM family members were expressed in wild-type BMMCs and wild-type LMCs, as previously reported [40].STXBP1 does not Impair in vitro IgE-dependent Mast Cell Degranulation, Intracellular Calcium Mobilization, or the Production of Reactive Oxygen Intermediates (ROI)Since STXBP1 plays a key role in eukaryotic trafficking, such as neurotransmitter release in neurons [39], granule release in platelets [22,41], etc, and since other SM family proteins, such as STXBP2 and STXBP3 are involved in mast cell degranulation [9], we set out to address the role of STXBP1 in mast cell degranulation. To examine whether deficiency of STXBP1 affected mast cell degranulation in vitro, STXBP1+/+ and STXBP12/2 LMCs were sensitized with anti-TNP IgE and stimulated with TNP-BSA for 20 minutes. The in vitro degranulation of LMCs was determined through Peptide M measurement of bhexosaminidase release. No impairment of b-hexosaminidase release in STXBP12/2 LMCs compared with WT LMCs was observed (Fig. 2A). Moreover, when histamine release was examined in this in vitro system, again no deficiency was detected in STXBP12/2 LMCs compared to wild-type cells (data not shown). Calcium influx is known to maintain and enhance signals after FceRI-mediated activation. To examine the role of STXBP1 in mast cell calcium mobilization, STXBP12/2 and STXBP1+/+ LMCs were sensitized with anti-TNP IgE and preloaded with Fura-2 AM followed by stimulation with 
TNP-BSA., No impairment in calcium mobilization was observed following FceRImediated activation (Fig. 2B).Statistical AnalysisThe paired Student’s t test was used for statistical evaluation of data. Results were considered significant when p,0.05. Data are expressed as means 6 SEM.Results STXBP1 Deficiency does not Impair Mast Cell MaturationSince STXBP1-deficient mice die prematurely due to an absence of neurotransmitter secretion in the brain [39], it is not feasible toSTXBP1 Is Not Required for AllergyFigure 1. STXBP1 is not required for mast cell maturation. A, Wild type, STXBP1 mutant, or AKT inhibitor 2 heterozygous mice were identified by PCR using DNA from liver cells. B, After 4? weeks of culture, liver-derived mast cells (LMC) were examined by toluidine blue staining to determine mast cell purity. A representative photomicrograph is shown (original magnification =6100). C, LMCs were sensitized with anti-TNP IgE, stained with FITCconjugated anti-IgE or anti-c-kit antibodies, and examined by flow cytometry. D, STXBP1+/+ and STXBP12/2 LMCs were sensitized with anti-TNP IgE and stimulated with TNP-BSA (10 ng/ml) for various times. Whole cell lysates were analyzed by Western blotting for STXBP1 and Actin. E, Sec1/ Munc18 (SM) family gene expression profiles were identified by RT-PCR using mRNA from wild type mouse bone marrow-derived mast cells (BMMC), and wild type (STXBP1+/+) or STXBP12/2 LMCs, with or without TNP-BSA stimulation. All members of SM family are expressed in wild type BMMCs and LMCs. Similar results were observed in 2 independent experiments. doi:10.1371/journal.pone.0058560.gPrevious studies have de.Xpression level of other sec1/munc18 family members, STXBP1+/+ and 1379592 STXBP12/2 LMCs were sensitized with anti-TNP IgE overnight and stimulated with TNP-BSA for 90 minutes or left untreated (NT). Gene expression was analyzed by RT-PCR using mRNA isolated from these cells. As expected, expression of the STXBP1 gene in STXBP12/2 LMC was not detected, while the expression of other members of the SM family were unimpaired (Fig. 1E). Indeed, all SM family members were expressed in wild-type BMMCs and wild-type LMCs, as previously reported [40].STXBP1 does not Impair in vitro IgE-dependent Mast Cell Degranulation, Intracellular Calcium Mobilization, or the Production of Reactive Oxygen Intermediates (ROI)Since STXBP1 plays a key role in eukaryotic trafficking, such as neurotransmitter release in neurons [39], granule release in platelets [22,41], etc, and since other SM family proteins, such as STXBP2 and STXBP3 are involved in mast cell degranulation [9], we set out to address the role of STXBP1 in mast cell degranulation. To examine whether deficiency of STXBP1 affected mast cell degranulation in vitro, STXBP1+/+ and STXBP12/2 LMCs were sensitized with anti-TNP IgE and stimulated with TNP-BSA for 20 minutes. The in vitro degranulation of LMCs was determined through measurement of bhexosaminidase release. No impairment of b-hexosaminidase release in STXBP12/2 LMCs compared with WT LMCs was observed (Fig. 2A). Moreover, when histamine release was examined in this in vitro system, again no deficiency was detected in STXBP12/2 LMCs compared to wild-type cells (data not shown). Calcium influx is known to maintain and enhance signals after FceRI-mediated activation. To examine the role of STXBP1 in mast cell calcium mobilization, STXBP12/2 and STXBP1+/+ LMCs were sensitized with anti-TNP IgE and preloaded with Fura-2 AM followed by stimulation with TNP-BSA., No impairment in calcium mobilization was observed following FceRImediated activation (Fig. 2B).Statistical AnalysisThe paired Student’s t test was used for statistical evaluation of data. Results were considered significant when p,0.05. Data are expressed as means 6 SEM.Results STXBP1 Deficiency does not Impair Mast Cell MaturationSince STXBP1-deficient mice die prematurely due to an absence of neurotransmitter secretion in the 
brain [39], it is not feasible toSTXBP1 Is Not Required for AllergyFigure 1. STXBP1 is not required for mast cell maturation. A, Wild type, STXBP1 mutant, or heterozygous mice were identified by PCR using DNA from liver cells. B, After 4? weeks of culture, liver-derived mast cells (LMC) were examined by toluidine blue staining to determine mast cell purity. A representative photomicrograph is shown (original magnification =6100). C, LMCs were sensitized with anti-TNP IgE, stained with FITCconjugated anti-IgE or anti-c-kit antibodies, and examined by flow cytometry. D, STXBP1+/+ and STXBP12/2 LMCs were sensitized with anti-TNP IgE and stimulated with TNP-BSA (10 ng/ml) for various times. Whole cell lysates were analyzed by Western blotting for STXBP1 and Actin. E, Sec1/ Munc18 (SM) family gene expression profiles were identified by RT-PCR using mRNA from wild type mouse bone marrow-derived mast cells (BMMC), and wild type (STXBP1+/+) or STXBP12/2 LMCs, with or without TNP-BSA stimulation. All members of SM family are expressed in wild type BMMCs and LMCs. Similar results were observed in 2 independent experiments. doi:10.1371/journal.pone.0058560.gPrevious studies have de.
