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Supplementary Information to Dissecting spatio-temporal protein networks driving human heart development and related disorders Kasper Lage1-5*, Kjeld Møllgård6, Steven Greenway7, Hiroko Wakimoto7, Joshua M. Gorham7, Christopher T. Workman4, Eske Bendsen8, Niclas T. Hansen4, Olga Rigina4, Francisco S. Roque4,5, Cornelia Weise9, Vincent M. Cristoffels9, Amy E Roberts10,11, Leslie B. Smoot11, William T. Pu11,12, Patricia K. Donahoe1,2,3, Niels Tommerup13, Søren Brunak4,5, Christine E Seidman7, Jonathan G Seidman7, Lars A. Larsen13* 1 Pediatric Surgical Research Laboratories, MassGeneral Hospital for Children, Massachusetts General Hospital, Boston, Massachusetts, USA. 2 Harvard Medical School, Boston, Massachusetts, USA. 3 Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA. 4 Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark. 5 Center for Protein Research, University of Copenhagen, Copenhagen, Denmark. 6 Developmental Biology Unit, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark. 7 Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA 8 Fertility Clinic, Department of Obstetrics and Gynaecology, University Hospital of Odense, Odense, Denmark 9 Center for Heart Failure Research, Academic Medical Centre, Amsterdam, The Netherlands. 10 Partners HealthCare Center for Genetics and Genomics, Boston, Massachusetts, USA 11 Department of Cardiology, Children's Hospital, Boston, Massachusetts, USA 12 Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts, USA. 13 Wilhelm Johannsen Centre for Functional Genome Research, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark. *Corresponding authors. K Lage, Pediatric Surgical Research Laboratory, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA, Tel.: +1 617 840 1799; Fax +1 617 726 5075; E-mail: [email protected] or LA Larsen , Wilhelm Johannsen Centre for Functional Genome Research, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark; Tel: +45 35327827; Fax +45 4535327845; E-mail: [email protected] 1 TABLE OF CONTENTS Supplementary text Supplementary experimental procedures References Table S1-S7 Figure S1-S15 2 SUPPLEMENTARY TEXT Generating a set of candidates for IH and expression profiling. Developing a score for identifying novel heart developmental candidates To systematically identify a set of proteins for validation of proteins and clusters in the networks, we made a set of raw candidates by determining a set of proteins that significantly interact with the 255 CD proteins using hyper geometric statistics. We first scored all 8,800 proteins in our protein interaction database based on their interaction pattern to the 255 CD proteins. Candidates were scored using the enrichment of CD proteins in their first order interaction network. The score assigned to a candidate was the hypergeometric p value of observing the amount of interactions to the CD set out of all interaction partners of the candidate (Figure S5A). For example: NKX2-5 has a total of seven interaction partners in our network of which five are other CD proteins. The hypergeometric probabillity that five of seven interaction partners are from the CD set (which constitutes less than 2% of the proteins with interactions in our interaction data) is p = 2.4e-06, which is the score of NKX2-5. Similarly, GATA4 has six interaction partners in our network of which three are other CD proteins, yielding a score p = 4.7e-4; and JAG1 has 13 interaction partners of which five are CD proteins yielding a score p = 1.5e-6. As expected, the first order network of JAG1 includes most of the known NOTCH pathway components (Ilagan and Kopan, 2007), thus supporting the biological signal of the interaction data in our network. 3 To see how well the hypergeometric pvalues correlate with the likelihood of being involved in cardiac development we calculated unadjusted p values for all CD proteins that have interactions in our network, and for a set of randomly chosen negative proteins not known to be involved in heart development. We then correlated the p values with the likelihood that a given protein is involved in heart development and see that these values are clearly correlated, indicating that the lower the p value of interactions to the CD set, the more likely a given protein is to be involved in heart developmental processes itself (Figure S5B). To be sure that this analysis was not positively biased in relation to the CD proteins and heart developmental processes we analyzed the interaction dataset for positive bias. Analyzing the interaction data for positive bias on relation to heart developmental processes First, due to the incorporation of hundreds of systematic large-scale interaction screens in our protein network the CD proteins should in principle not be better studied than the randomly chosen proteins and thus bias the significance assessment. However, to be sure that this was actually the case we confirmed that the random set of proteins had a similar distribution of interactions when compared to the 255 heart development proteins, suggesting that the amount of interaction data for the CD proteins and other proteins in the network does not differ (data not shown). Second, by text-mining PubMed we identified a small set of publications that described proteomic analyses of proteins involved in congenital heart defects and heart development. We then cross referenced this set of publications with the publications reporting data used in our protein interaction 4 network and found that there was no overlap, meaning that if they for some reason had not been included in the protein interaction databases we draw our data from, and that none of the thousands of interaction screens incorporated in our network were produced in an attempt to study congenital heart defects or heart development. This shows that our predictions should not be positively biased towards known CD proteins. Scoring all proteins in our database to identify novel heart developmental candidate proteins To identify likely novel candidates we then made a proteome-scale rank of all proteins with interaction data in our network, and identified a list of 70 proteins that had a significant pvalues after correction for multiple testing. The pvalue threshold for proteome-wide significance is indicated by the red dashed line in Figure S5B. Twenty one of 70 proteins are from the CD set yielding a set of 49 candidates (Table S2). We then analyzed how many of these candidates had been described in the context of relevant processes in the literature in PubMed and only considered them novel in relation to heart development, if they were undescribed in this regard (http://www.ncbi.nlm.nih.gov/pubmed/). Of the 49 candidates nineteen result in a cardiac or vascular phenotype when mutated in mice (Table S2). There are several explanations to why these 19 proteins were not in the input data; i) vascular phenotypes were not among the phenotypes we choose for our input data-set, ii) some of the data has been added to a later version of the MGI database and iii) database curator errors. Nevertheless, the large proportion of candidate genes associated with vascular or cardiac phenotypes in mice support that this group of genes are involved in heart development. 5 Using the morphological sub-groups to predict spatio-temporal function of the 49 candidates and to select 12 specific candidates for IH analysis. To validate further the identified 49 candidates and systematically identify the most likely developmental stages and processes in which each were involved, we used the morphological subgroups associated with the known CD proteins (Table S1) to infer developmental functions to the interacting candidates. We used a hypergeometric based score as described above, but for this analysis each candidate was assigned a score to the specific morphological subgroups depending on their interaction pattern to proteins represented in these specific groups. For example, the candidate SNX9 interacts with ADAM9 and ADAM15 from the morphological subgroups ‘abnormal atrioventricular valve morphology’ (AAVM) (Figure S2C), and ADAM9, ADAM15, and EGFR from the subgroup ‘abnormal semilunar valve morphology’ (ASVM) (Figure S6A). This interaction pattern yields scores to these two groups with adjusted (using a Bonferroni correction) p values 6.6e-3 and 3.1e-4 respectively and SNX9 is coloured in Figure S2C and Figure S3A according to these p values. SNX9 also interacts with TMOD1, from ‘abnormal heart tube morphology’ (AHTM), ‘abnormal looping morphogenesis’ (ALM), the subgroups ‘abnormal myocardial fiber morphology’ (AMFM) and ‘abnormal myocardial trabeculae morphology’ (AMTM). However, TMOD1 is the only interaction partner of SNX9 in these groups, and the interactions do not yield significant association of SNX9 to AHTM, ALM, AMFM and AMTM. Hereby, the analysis suggests that SNX9 has a role 6 specifically in valve formation. Similarly, JAG2 (Figure S5B) significantly interacts with proteins in the groups ‘abnormal sinus venosus’ (ASV) (Figure S1C), ‘atrial septal defect’ (ASD) (Figure S2A), ‘small heart’ (SH) (Figure S4F), ‘ventricular septal defect’ (VSD) (Figure S3D), and AMTM (Figure S5D), suggesting a role of JAG2 in septation and trabeculation (Figure S6B). We carried out this stratification for all 49 candidates and the 21 previously known CD proteins, the results can be seen in (Figure S6). Twelve of the 49 candidates were chosen for IH analysis based on the overlap between morphological subgroups and the developmental stages present in our panel of embryonic hearts available for validation experiments. 7 Validating the module maps by IH analyses of 12 candidates and two known CD proteins. For validation of the module maps we analyzed the spatial and temporal expression pattern of 14 proteins in the network (Table S4, Figure S7-S13). A total of 382 tissue sections from 19 human hearts were used, and the expression pattern in each tissues section was determined in a completely standardized fashion by the same person. Using this table we estimated the precision of our functional predictions by seeing how often the expression in a specific tissues and at a specific time point, correlated with our functional predictions. To be conservative we only considered a prediction to be true if the tissue and developmental stage corresponding to the function, showed the highest degree of expression for the relevant protein (Table S5). Precision was then calculated in a standardized manner as the amount of true positive predictions (TP) divided by the sum of TP and false positive (FP) predictions, which yielded a precision of 0.72, showing the strong biological signal in our networks. As positive controls we used the proteins EGFR and BMP4 which are known heart developmental proteins in mice. In our network, the proteins represent clusters of ERBB signalling and TGFbeta/BMP signalling, respectively. The network analysis suggest diverse roles of TGFbeta/BMP and ERBB signalling modules in human heart development, which is supported by the IH analyses (Table S4). In particular, the involvment of ERBB signalling in development of the semilunar (SL) and 8 atrioventricular (AV) valves and the involvment of TGFbeta/BMP signalling in development of the SL valves are supported by the IH analyses. A module of unknown function containing SNX9 is involved in development of the cardiac valves We identified a distinct PPI subcluster associated with development of the cardiac valves (Figure S2C and S3A). We were not able to assign a specific function to this subcluster, but a function in regulation of ERBB signalling and endothelial-mesenchymal transformation (EMT) is likely. SNX9 has been shown to regulate the endocytosis of EGFR (Lin et al., 2002). The cluster includes several members of the family of metalloproteases known as “a disintegrin and metalloprotease (ADAM)”. Proteins of the ADAM family have been implicated in ectodomain shedding of epidermal growthfactor receptor (EGFR) ligands (Blobel, 2005). The protein SH3PXD2A (SH3MD1, Tks5) is also included in this subcluster. SH3PXD2A is involved in degradation of the extracellular matrix and cell invasion (Seals et al., 2005). The specific expression of SNX9 within the endothelial cells lining the surface of endocardial cushions in the aortic trunk supports a role of this subcluster in EMT. During development of the EC endothelial cells receive signals from the underlying myocardium and transform into mesenchymal cells which invade the underlying cardiac jelly (Armstrong and Bischoff, 2004). 9 Notch Signalling is Involved in Several Aspects of Cardiac Morphology Hierachical clustering of 70 CD candidate proteins show that several proteins involved in Notch signalling is associated with a specific subset of morphological phenotypes (Figure S6C). These include abnormal sinus venosus, trabeculation, septal defects and double outlet right ventricle (DORV) - a condition in which both great arteries arise from the right ventricle. By IH analysis of a 6th week human embryonic heart, we were able to investigate the relationship between DLL1, JAG2,NOTCH3 and NOTCH4 and some of the morphological phenotypes these CD candidates were predicted to be involved in. We observed strong DLL1 expression in the endothelial cells lining the developing atrial septum (AS) with the strongest expression at the leading edge of the AS (Figure S9C-E). Furthermore we observed strong expression of NOTCH3 and JAG2 in endothelial cells aligning the left atrial side of the endocardial cushion (EC) (Figure S8C, D and S9A) and strong expression of DLL1 in cells within the EC (Figure S8A). These expression patterns support a role of Notch signaling in atrial septation since fusion of the EC with the mesenchymal cap of the leading edge of the primary AS is an important event in atrial septation (Anderson et al., 2003; Kirby, 2007; Mommersteeg et al., 2006). The ventricular septum (VS) is composed of a muscular part and a membranous part. Development of the muscular part of the VS is, at least in part, achieved by the 10 compaction of trabeculae (Contreras-Ramos et al., 2008; Kirby, 2007; Stadtfeld et al., 2007). The membranous part of the VS is formed from cushion tissue in the outflow tract (Kirby, 2007). The IH analysis of DLL1, JAG2 and NOTCH3 support involvement of Notch signaling in ventricular septation as we observed expression of all three proteins in endothelial cells lining the developing trabeculae of the ventricle (Figure S8A-C, E and S9A) and strong expression of NOTCH3 and JAG2 in endothelial cells of the outflow tract and in the cardiac cushions of the outflow tract (Figure S8C and S9A,B). The predicted involvement of Notch signaling in cardiac septation and DORV (Figure S2A, S3C,D) implies that mutations in the Notch signaling pathway should be found in a subset of patients with atrial septal defects (ASD), ventricular septal defect (VSD), DORV and tetralogy of Fallot (ToF). This hypothesis is in part supported by the clinical phenotype of patients with mutations in JAG1, NOTCH1 and NOTCH2 (Eldadah et al., 2001; Garg et al., 2005; McElhinney et al., 2002). JAG1 and NOTCH2 mutations are found in patients with Alagille syndrome (McDaniell et al., 2006; Warthen et al., 2006). The most prevalent cardiac defect in Alagille syndrome is pulmonary stenosis, but 1/5 of the patients have ASD, VSD or ToF (McElhinney et al., 2002). ToF is caused by malalignment of the conal part of the ventricular septum, which results in VSD, pulmonary stenosis, bi-ventricular connection of the aorta and right ventricular hypertrophy (Anderson and Weinberg, 2005). From a developmental point of view 11 DORV and ToF are very similar, but DORV represent a more extreme septal malalignment. Furthermore, JAG1 mutations have been reported in familial ToF (Eldadah et al., 2001) and in relatives to AS patients with isolated ASD and ToF (Krantz et al., 1999). ASD, VSD, DORV and ToF were observed in a subset of the affected family members in two families segregating NOTCH1 mutations (Garg et al., 2005). And interestingly, two out of ten de novo CNVs identified in patients with ToF contains NOTCH1 and JAG1, respectively (Greenway et al., 2009). The functional prediction of CD candidates also suggests an involvement of Notch signaling in trabeculation (Figure S6C, S2D). Our IH analysis showed that DLL1, JAG2 and NOTCH3 were expressed in the developing trabeculae (Figure S8A-C, E and S9A) in line with recent data (Grego-Bessa et al., 2007). However, our analysis does not predict involvement of Notch signalling in development of the cardiac valves (Figure S6C) although such a connection is well established (High and Epstein, 2008). This is due to the fact that valve defects were not among the phenotypes reported for mice with targeted mutations in Notch signalling proteins (Table S1) thus this is an example of the shortcommings of our strategy. 12 In summary, our analysis associates most of the proteins known to be involved in Notch signaling with specific events in cardiac development and we hypothesize that mutation in any of these proteins could lead to ASD, VSD, ToF or DORV in humans. PPI modules and candidates associated with myocardial growth and organisation Several PPI subclusters and a large proportion of the CD candidate proteins are involved in myocardial growth and organisation (Figures S6C and S4). IH analysis of seven of the proteins associated with myocardial development show that all proteins are expressed in the cardiomyocytes (Table S4, Figures S10, S11 and S13). Furthermore, the staining patterns suggested a spatial regulation of PTGS2 and CAV3 and a temporal regulation of BMX during cardiac development. Thus, the IH analysis supports a function in myocardial development of these proteins. The candidates belonging to the group of proteins associated with myocardial development can be divided further into three subgroups, which mainly differ by the proteins involvement in signalling transduction (Figure S6C, D). The candidate proteins in two of these subgroups are involved in a large number of signalling pathways. Examples of proteins within these groups are members of the RAS, SOS, MAPK and AKT families. Thus, these subgroups probably represent proteins involved in cross-talk between signalling pathways influencing the growth and organisation of the myocardium. The protein-protein interactions plotted in Figure S4 also suggest the existence of extensive signalling crosstalk during myocardial development. 13 Independent validation of the network data and module maps by expression profiling across 12 developmental time points To validate the network data and module maps we carried out expression profiling of all 49 novel candidates determined by their interaction profile to set of 255 CD proteins in the previous section. This analysis was carried out using RNA extracted from 14 embryonic human hearts. We chose quantitative real-time quantitative RT-PCR for this analysis because it is considered to be the most accurate and sensitive method for detecting RNA differences also at very small amounts (Lang et al, 2009). First we analyzed the expression of 44 candidates, across two developmental time points and compared the differential expression of candidates to a set of 29 negative controls. For this analysis RNA was extracted from two human hearts at 46 days and 67 days post fertilization. The relative difference in the level of gene expression between day 46 and 67 were significantly larger in the group of candidates (median=0.44) compared to the group of negative controls (median=0.14) when compared using a Mann-Whitney (Wilcoxon) W test (p<0.006, Figure 3R), showing that the set of candidates are significantly more differentially expressed than the control set, indicating that a significant proportion of the candidates are temporally regulated across the two developmental time points. To investigate this trend in more detail, we analyzed the relative expression levels of a subset of the candidates in 12 additional hearts at 12 different time points between 40 and 67 days post fertilization. It was not possible to analyze all the candidates due to 14 limitations in the human heart material, but a large proportion (18 of 49), was tested. This analysis showed that half of the candidates were significantly differentially expressed across the two time points further supporting their role in heart development (Figure 3SW). To further validate the candidates and exclude that polymorphic gene expression between the individual developing hearts used in the previous analysis could account for the observed differential and temporal expression trends, we also used Polony Multiplex Analysis of Gene Expression (PMAGE) (Kim et al., 2007) to measure the expression of the 49 candidates in right ventricular outflow tract (RVOT) from TOF patients at the time of primary surgical repair and left ventricle (LV) collected from patients with either heart failure or diabetic cardiomyopathy. The expression levels of the candidates were compared to the expression levels of a different set of 49 randomly chosen controls after normalizing both gene sets against gene expression in glioblastoma tissue. Here, the heart developmental candidates were significantly higher expressed in heart tissue than the controls (p = 0.016, Figure S13 and below). In conclusion, the expression profiling experiments show that novel heart developmental genes can be identified by systematically analyzing the interaction patterns of the 255 known CD proteins. These results serve as an independent validation of the network data and module maps. 15 Focal adhesion signalling in cardiac development An interesting observation, which can be derived from the map of functional modules, is the implication of focal adhesion signalling in several aspects of cardiac development (Figure 2, Figures S1A, S2D, S3A, S4A, B, D, and E). Focal adhesion signalling is important for regulation of cell migration, cell proliferation and growth factor signalling (Mitra et al., 2005). Although such events are regarded as key elements in heart development, the focus on focal adhesion signalling in heart development has so far been limited. However, very recent investigations have shown that conditional targeted deletion of the Focal adhesion kinase (Fak) gene in mice results in CHD (Hakim et al., 2007; Peng et al., 2008). FAK (PTK2) was not included in our list of input proteins due to the recent publication of the knockout studies, and our network data precedes knowledge of FAKs involvement in heart development (see below). Thus, the phenotypes associated with defective focal adhesion signalling in mouse models are another functional verification of the predictive power of the networks. The publications reporting the involvement of focal adhesion signalling by FAK mutations in heart development are from May 2007 (Hakim et al., 2007) and April 2008 (Peng et al., 2008) respectively. The networks reported here were all generated in January 2008, using data downloaded two months before. Thus, the only possibility of bias is the article by Hakim et al. To investigate the putative bias we investigated if the Hakim et al. publication was represented in our PPI data and used to construct our networks, which was not the case. We then tracked down all publications citing the Hakim et al., publication. None of these articles were published before our networks were generated 16 and none of these articles affect the data represented in our networks making it highly unlikely that our findings are biased by the Hakim et al., publications and supporting the predictive power of our networks. Modules of cardiac progenitor cell growth and differentiation Several of the functional modules identified in this study are known to be involved in growth and differentiation of cardiac progenitor cells. These include markers for progenitor cells in the first heart field (TBX5) and second heart field (ISL1) (Domian et al, 2009; Moretti et al, 2006) and functional modules involved in differentiation of cardiac progenitors (e.g. transcription modules; Notch signaling modules; WNT signaling modules and BMP/TGFbeta signaling modules (Dyer & Kirby, 2009; Kwon et al, 2009; Moretti et al, 2006). Thus, the map of functional modules presented here may aid in the discovery of new factors involved in growth and differentiation of cardiac progenitors and in the illumination of molecular events involved in cardiomyogenesis. 17 SUPPLEMENTARY EXPERIMENTAL PROCEDURES PPI Data We have previously generated and thoroughly validated an experimentally derived human protein interaction network which is described in detail in (Lage et al., 2007; Lage et al., 2008), which integrates and refines experimental proteomic data from more than 13 million articles in Medline. Interested readers can consult these publications and the online information harbored at: http://www.cbs.dtu.dk/suppl/dgf/phenome_interactome/index.php, click on the ‘Methods’ link, for the details on generating this interaction resource. The resulting network includes many unbiased large-scale proteomics datasets, meaning we are not confined to exploring only existing well-known pathways. An updated version of this network, containing 12,507 human proteins connected by a total of 350,029 unique interactions, was used in this work. The underlying data in this network stems from the databases BIND (Bader et al., 2003), MINT (Zanzoni et al., 2002), IntAct (Hermjakob et al., 2004), KEGG (Kanehisa et al., 2006), Reactome (Franke et al., 2006), HPRD (Peri et al., 2003), DIP (Salwinski et al., 2004) and GRID (Breitkreutz et al., 2003). Data is transferred between organisms using the Inparanoid orthology database (O'Brien et al., 2005) as previously described in the aforementioned publications. 18 Differential expression in human heart tissues measured by PMAGE Expression libraries were created from RNA isolated from right ventricular outflow tract tissue collected from four TOF patients at the time of primary surgical repair (mean patient age 2.6 ± 2 months), left ventricle collected from patients with either heart failure or diabetic cardiomyopathy. Tissue was snap-frozen in liquid nitrogen and maintained at –80˚C prior to processing. RNA extraction and library construction and amplification was carried out as previously described (Kim et al., 2007). Amplified library was sequenced on a Illumina Genome Analyzer (Illumina, San Diego, CA). Each library generated more than 2,000,000 reads with a Chastity score (Illumina, San Diego, CA) > 2. Sense tags were assigned to cognate gene identities and unique tags assigned to the same UniGene cluster or gene symbol were combined. For candidates and controls we measured the fold difference by dividing the tag count in RVOT or LV by the tag count in glioblastoma (collected and analyzed by the same method) and treated all data points independently. We pooled the RVOT and LV data points to make the final distributions, meaning that candidate or control gene is represented by 6 data points in the distribution (4 from RVOT and 2 from LV), ensuring robustness. The fold expression difference distributions were compared using a Mann-Whitney u-test. 19 REFERENCES Anderson, RH, Webb, S, Brown, NA, Lamers, W, Moorman, A (2003) Development of the heart: (2) Septation of the atriums and ventricles. Heart 89: 949-958. Anderson, RHWeinberg, PM (2005) The clinical anatomy of tetralogy of fallot. Cardiol Young 15 Suppl 1: 38-47. 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