Cell type-specific chromatin immunoprecipitation from multicellular complex samples using BiTS-ChIP.
Bonn, S., Zinzen, R.P., Perez-Gonzalez, A., Riddell, A., Gavin, A.C. & Furlong, E.E.
Nat Protoc. 2012 Apr 26;7(5):978-94. doi: 10.1038/nprot.2012.049.
This protocol describes the batch isolation of tissue-specific chromatin for immunoprecipitation (BiTS-ChIP) for analysis of histone modifications, transcription factor binding, or polymerase occupancy within the context of a multicellular organism or tissue. Embryos expressing a cell type-specific nuclear marker are formaldehyde cross-linked and then subjected to dissociation. Fixed nuclei are isolated and sorted using FACS on the basis of the cell type-specific nuclear marker. Tissue-specific chromatin is extracted, sheared by sonication and used for ChIP-seq or other analyses. The key advantages of this method are the covalent cross-linking before embryo dissociation, which preserves the transcriptional context, and the use of FACS of nuclei, yielding very high purity. The protocol has been optimized for Drosophila, but with minor modifications should be applicable to any model system. The full protocol, including sorting, immunoprecipitation and generation of sequencing libraries, can be completed within 5 d.
Tissue-specific analysis of chromatin state identifies temporal signatures of enhancer activity during embryonic development.
Bonn, S., Zinzen, R.P., Girardot, C., Gustafson, E.H., Perez-Gonzalez, A., Delhomme, N., Ghavi-Helm, Y., Wilczynski, B., Riddell, A. & Furlong, E.E.
Nat Genet. 2012 Jan 8;44(2):148-56. doi: 10.1038/ng.1064.
Chromatin modifications are associated with many aspects of gene expression, yet their role in cellular transitions during development remains elusive. Here, we use a new approach to obtain cell type-specific information on chromatin state and RNA polymerase II (Pol II) occupancy within the multicellular Drosophila melanogaster embryo. We directly assessed the relationship between chromatin modifications and the spatio-temporal activity of enhancers. Rather than having a unique chromatin state, active developmental enhancers show heterogeneous histone modifications and Pol II occupancy. Despite this complexity, combined chromatin signatures and Pol II presence are sufficient to predict enhancer activity de novo. Pol II recruitment is highly predictive of the timing of enhancer activity and seems dependent on the timing and location of transcription factor binding. Chromatin modifications typically demarcate large regulatory regions encompassing multiple enhancers, whereas local changes in nucleosome positioning and Pol II occupancy delineate single active enhancers. This cell type-specific view identifies dynamic enhancer usage, an essential step in deciphering developmental networks.
Regulatory T cells contribute to diabetes protection in lipopolysaccharide-treated non-obese diabetic mice.
Caramalho, I., Rodrigues-Duarte, L., Perez, A., Zelenay, S., Penha-Goncalves, C. & Demengeot, J.
Scand J Immunol. 2011 Dec;74(6):585-95. doi: 10.1111/j.1365-3083.2011.02627.x.
It is well established that viral, parasitic or bacterial infections can prevent type 1 diabetes (T1D) occurrence in non-obese diabetic (NOD) mice. On the other hand, defects in CD4(+) Regulatory T cell (Treg) numbers and/or function contribute to T1D aetiology in NOD mice and in humans. In this work, we formally tested whether the protective role of the bacterial product lipopolysaccharide (LPS) on diabetes incidence results from enhanced Treg activity. We first report that weekly administration of LPS to young prediabetic NOD mice, presenting or not insulitis at the time of treatment, afforded full protection from diabetes. Taking advantage from the high but incomplete penetrance of diabetes in NOD mice raised in specific pathogen free (SPF) conditions we compared untreated disease-free old animals with gender- and age-matched LPS-treated mice. Histological and flow cytometry analysis indicated that LPS treatment did not prevent islet infiltration or priming of diabetogenic T cells but increased Foxp3(+) and CD103(+) Treg frequency and numbers. By performing adoptive transfer experiments into alymphoid NOD/SCID recipients, we further demonstrated that CD25(+) cells from LPS-treated NOD mice, but not from naturally protected animals, maintained diabetogenic cells at check. Our study suggests that T cell regulation represents a cellular mechanism to explain the 'hygiene hypothesis' and reinforces the notion that immune activity consolidates dominant tolerance.
Sphingosine kinase-1 (SphK-1) regulates Mycobacterium smegmatis infection in macrophages.
Prakash, H., Luth, A., Grinkina, N., Holzer, D., Wadgaonkar, R., Gonzalez, A.P., Anes, E. & Kleuser, B.
PLoS One. 2010 May 17;5(5):e10657. doi: 10.1371/journal.pone.0010657.
Sphingosine kinase-1 is known to mediate Mycobacterium smegmatis induced inflammatory responses in macrophages, but its role in controlling infection has not been reported to date. We aimed to unravel the significance of SphK-1 in controlling M. smegmatis infection in RAW 264.7 macrophages. Our results demonstrated for the first time that selective inhibition of SphK-1 by either D, L threo dihydrosphingosine (DHS; a competitive inhibitor of Sphk-1) or Sphk-1 siRNA rendered RAW macrophages sensitive to M. smegmatis infection. This was due to the reduction in the expression of iNOs, p38, pp-38, late phagosomal marker, LAMP-2 and stabilization of the RelA (pp-65) subunit of NF-kappaB. This led to a reduction in the generation of NO and secretion of TNF-alpha in infected macrophages. Congruently, overexpression of SphK-1 conferred resistance in macrophages to infection which was due to enhancement in the generation of NO and expression of iNOs, pp38 and LAMP-2. In addition, our results also unraveled a novel regulation of p38MAPK by SphK-1 during M. smegmatis infection and generation of NO in macrophages. Enhanced NO generation and expression of iNOs in SphK-1++ infected macrophages demonstrated their M-1(bright) phenotype of these macrophages. These findings thus suggested a novel antimycobacterial role of SphK-1 in macrophages.
Role of lipids in killing mycobacteria by macrophages: evidence for NF-kappaB-dependent and -independent killing induced by different lipids.
Gutierrez, M.G., Gonzalez, A.P., Anes, E. & Griffiths, G.
Cell Microbiol. 2009 Mar;11(3):406-20. Epub 2008 Nov 7.
We have shown that several lipids can modulate the macrophage innate immune response against mycobacteria and enhance their killing. Since NF-kappaB is required for mycobacterial killing, we tested the ability of lipids to activate NF-kappaB in uninfected macrophages and those infected with mycobacteria. In uninfected cells, sphingomyelin (SM), phosphatidylinositol-4-phosphate (PIP) and arachidonic acid (AA) enhanced NF-kappaB activation and the cell surface expression of CD69, a macrophage activation marker regulated by NF-kappaB. Sphingosine (Sph), sphingosine-1-phosphate (S1P), diacylglycerol (DAG), eicosapentanoic acid (EPA) and phosphatidyl choline (PC) failed to activate either NF-kappaB or CD69. Ceramide (Cer) activated CD69 expression without activating NF-kappaB. In Mycobacterium smegmatis-infected cells, NF-kappaB was transiently activated in a manner that was enhanced by SM, PIP and AA. In contrast Mycobacterium avium mostly repressed NF-kappaB activation and only SM and AA could induce its partial activation. While lipids that activate NF-kappaB in uninfected cells tend to kill mycobacteria in macrophages Sph and S1P failed to activate NF-kappaB under most conditions but nevertheless enhanced killing of M. smegmatis, M. avium and M. tuberculosis H37Rv. Our results argue that both NF-kappaB-dependent and -independent mechanisms are involved in macrophage killing of mycobacteria and that both mechanisms can be enhanced by selected lipids.
Generation and characterization of an anti-idiotype monoclonal antibody related to GM3(NeuGc) ganglioside.
Rodriguez, M., Llanes, L., Perez, A., Perez, R. & Vazquez, A.M.
Hybrid Hybridomics. 2003 Oct;22(5):307-14.
The 14F7 monoclonal antibody (MAb), IgG1 isotype, which reacts specifically to GM3(NeuGc) ganglioside induced a specific IgG anti-idiotypic antibody (Ab2) response in syngeneic mice when it was administered coupled with KLH and in the presence of Freund's adjuvant. Spleen cells from these mice were used in somatic-cell hybridization experiments using the murine myeloma cell line P3-X63-Ag8 653 as fusion partner. An IgG1 Ab2 MAb was selected. This Ab2 MAb, called 4G9, was able to block the binding of 14F7 MAb to GM3(NeuGc) ganglioside and developed a strong IgG anti-anti-idiotypic antibody (Ab3) response, when injected into syngeneic mice. These Ab3 antibodies were characterized to bear 14F7 MAb idiotopes, but did not have the same specificity as 14F7 MAb. In the other hand, a very specific anti-NeuGc-containing ganglioside response was generated in chickens immunized with this Ab2 MAb, thus behaving, in this species as an "internal image" antibody.
Chimeric anti-N-glycolyl-ganglioside and its anti-idiotypic MAbs: immunodominance of their variable regions.
Lopez-Requena, A., Mateo de Acosta, C., Perez, A., Valle, A., Lombardero, J., Sosa, K., Perez, R. & Vazquez, A.M.
Hybrid Hybridomics. 2003 Aug;22(4):235-43.
P3 monoclonal antibody (MAb) is a murine IgM that specifically recognizes N-glycolyl (NeuGc)-gangliosides and sulfatides. It also reacts with antigens expressed in human breast tumors and melanoma. In syngeneic model, P3 MAb is able to elicit a strong anti-idiotypic (Ab2) antibody response, even in the absence of adjuvants or carrier proteins. 1E10 MAb is an anti-idiotypic antibody specific for P3 MAb that has demonstrated anti-tumoral effects in syngeneic and allogeneic animals. Here we report the construction of the human IgG(1) chimeric P3 and 1E10 antibodies, and the evaluation of the maintenance of the main properties of the murine MAbs. Chimeric P3 antibody specifically reacted with GM3(NeuGc) and GM2(NeuGc) gangliosides, and not with their acetylated variants. Also, it strongly recognized the anti-idiotypic 1E10 MAb. Chimeric 1E10 antibody specifically reacted with P3 MAb. Upon immunization of Balb/c mice with both chimeric antibodies, we were able to demonstrate the immunodominance of their variable regions. The anti-idiotypic response induced by both antibodies was strong and in most of the mice was even significantly higher than the anti-isotypic response, despite the fact that 70% of the chimeric molecule is xenogenic with respect to the animal model.
A monoclonal antibody against NeuGc-containing gangliosides contains a regulatory idiotope involved in the interaction with B and T cells.
Perez, A., Mier, E.S., Vispo, N.S., Vazquez, A.M. & Perez Rodriguez, R.
Mol Immunol. 2002 Sep;39(1-2):103-12.
P3 (IgM-kappa) is a monoclonal antibody (mAb) reacting with N-glycolyl neuraminic acid (NeuGc)-containing gangliosides and sulfated glycolipids. To explore the nature of the idiotope defined by 1E10, we used a phage-displayed random peptide library. After three rounds of selection, seven different phagotopes were isolated. Noteworthy, all the sequences were found to bear the basic amino acid-rich motifs KPPR (3) or RRPR/K (4). This recursive selection of basic sequences by 1E10 mAb confirmed previous suggestions of the involvement of charged residues in the interaction between gamma-type Ab2 and P3 mAb. The binding of 1E10 to phage peptides representing each group was completely inhibited by P3 mAb. In addition, other Ab2 to P3 were able to recognize these peptides. Thus, phage peptides seem to be mimotopes of the idiotope recognized by anti-idiotypic antibodies in P3. Phage motifs were represented in the lineal sequence of P3's heavy chain H-CDR3 and a 14-mer peptide representing this region was able to specifically inhibit 1E10 binding to P3. Previous studies showed that P3's idiotype was autoimmunogenic and shared by antibodies with different specificities. Now, we demonstrated that P3 mAb is able to activate a network cascade involving autologous anti-idiotypic and anti-anti-idiotypic T cells. Thus, P3's idiotype fulfill the three criteria previously established to define a "regulatory idiotype". Particularly, data presented here revealed the immunodominance of the H-CDR3 of this mAb as a T cell epitope. Thus, H-CDR3 is simultaneously involved in the interaction of P3 mAb with anti-idiotypic B and T cells, behaving as a potential regulatory idiotope.
An anti-idiotype vaccine elicits a specific response to N-glycolyl sialic acid residues of glycoconjugates in melanoma patients.
Alfonso, M., Diaz, A., Hernandez, A.M., Perez, A., Rodriguez, E., Bitton, R., Perez, R. & Vazquez, A.M.
J Immunol. 2002 Mar 1;168(5):2523-9.
We generated the 1E10 gamma-type anti-idiotype mAb (Ab2) specific to an Ab1 mAb able to react specifically with N-glycolyl-containing gangliosides and with Ags expressed on human melanoma and breast carcinoma cells. This Ab2 mAb induced an Ab response in animal models sharing immunochemically defined idiotopes with the Ab1. The treatment of tumor-bearing mice with 1E10 mAb induced a strong antitumor activity. A clinical trial was conducted in 20 patients with advanced malignant melanoma. Patients were treated with six intradermal injections of aluminum hydroxide-precipitated 1E10 anti-Id mAb given at 2-wk intervals. Sixteen of the 17 patients who received at least four doses of the anti-Id vaccine develop Ab3 Abs capable of inhibiting Ab2 binding to Ab1 (Ab3Id+). In contrast to the incapacity of 1E10 mAb to generate Ab3 Abs with the same antigenic specificity as the Ab1 mAb in mice, a very specific and strong Ab3 response against N-glycolyl-containing gangliosides was induced in 16 patients (Ab3Ag+). No evidence of serious or unexpected adverse effects has been observed in this clinical trial. 1E10 anti-Id vaccine was safe, well tolerated, and immunologically effective, with most patients being able to generate a specific immune response against 1E10 and Neu-glycolyl-GM(3) ganglioside.
Immunogenetic analysis of variable regions encoding AB1 and gamma-type AB2 antibodies from the NeuGc-containing ganglioside family.
Perez, A., Lombardero, J., Mateo, C., Mustelier, G., Alfonso, M., Vazquez, A.M. & Perez, R.
Hybridoma. 2001 Aug;20(4):211-21.
The variable regions from P3, a murine monoclonal antibody (MAb) against NeuGc-containing gangliosides, and two anti-idiotype MAbs directed to P3 MAb were cloned and sequenced. Comparisons with previously reported sequences showed that P3 is a germline antibody encoded by genes from the V(H)Q52 and V(kappa)19 families. Analysis of nucleotides at the heavy chain CDR3 (H-CDR3) showed the presence of an extensive 3' N region that contains almost 50% of the nucleotides of this CDR. In addition, amino acid sequence analysis of the H-CDRs of this MAb revealed the presence of three arginines, two of which are present in the H-CDR3, that could be involved in the interaction of P3 MAb with its electronegative epitope on gangliosides. Anti-idiotype 1E10, which seems to define a "regulatory" idiotope on P3 MAb (it induces Id+ Ab3), represents a germline Ab2 that belongs to the V(H)J558 and V(kappa)10 gene families. By contrary, the anti-idiotype 3B11 is an extensively mutated antibody that belongs to the V(H)3660 and V(kappa)4/5 gene families, defining a "private" idiotope on P3 MAb. Even when different V genes contribute to the variable regions of 1E10 and 3B11 MAbs, they share an acidic motif E/D-D-Y/D-Y-D in H-CDR3, suggesting that both Ab2s recognize paratope positive residues on the Ab1. Therefore, complementary electrostatic interactions involving H-CDR3 from both Ab1 and Ab2, might provide a clue to understand the molecular basis for the generation of gamma-type anti-idiotype antibodies to V regions recognizing glycolylated ganglioside antigens.
Syngeneic anti-idiotypic monoclonal antibodies to an anti-NeuGc-containing ganglioside monoclonal antibody.
Vazquez, A.M., Perez, A., Hernandez, A.M., Macias, A., Alfonso, M., Bombino, G. & Perez, R.
Hybridoma. 1998 Dec;17(6):527-34.
An IgM monoclonal antibody (MAb), named P3, has the characteristic to react specifically with a broad battery of N-glycolyl containing-gangliosides and with antigens expressed on breast tumors. When this MAb was administered alone in syngeneic mice, an specific IgG anti-idiotypic antibody (Ab2) response was induced, this Ab2 response was increased when P3 MAb was injected coupled to a carrier protein and in the presence of Freund's adjuvant. Spleen cells from these mice were used in somatic-cell hybridization experiments, using the murine myeloma cell line P3-X63-Ag8.653 as fusion partner. Five Ab2 MAbs specific to P3 MAb were selected. These IgG1 Ab2 MAbs were able to block the binding of P3 MAb to GM3(NeuGc) ganglioside and to a human breast carcinoma cell line. Cross-blocking experiments demonstrated that these Ab2 MAbs are recognizing the same or very close sites on the Abl MAb. The five Ab2 MAbs were injected into syngeneic mice and four of them produced strong anti-anti-idiotypic antibody (Ab3) response. While these Ab2 MAbs were unable to generate Ab3 antibodies with the same antigenic specificity than P3 MAb, three of them induced antibodies bearing P3 MAb idiotopes (Ag-Id+ Ab3). These results demonstrated that these Ab2 MAbs are not "internal image" antibodies, but they could define "regulatory idiotopes."