Vincent Christoffels

• PhD
• Academisch Medisch Centrum Universiteit van Amsterdam

Trabecular muscle makes up most of the ventricular wall of the human embryo. It is presumed that compaction in the foetal period changes ventricular wall morphology by converting weaker trabeculae to stronger compact muscle. Using developmental series covering the embryonic and foetal periods of human, mouse and chicken, we show ventricular morphol...

Early heart morphogenesis involves a process in which embryonic precursor cells are instructed to form a cyclic contracting muscle tube connected to blood vessels, pumping fluid. Subsequently, the heart becomes structurally complex and its size increases several orders of magnitude to functionally keep up with the demands of the growing organism. P...

The components of the cardiac conduction system, responsible for coordinated activation of the heart chambers, are well defined and their cells differ in gene expression profile and phenotype from those of the surrounding working myocardium. Yet, when and on what basis the myocardium of each of the conduction system components become distinguishabl...

The rate of contraction of the heart relies on proper development and function of the sinoatrial node, which consists of a small heterogeneous cell population, including Tbx3+ pacemaker cells. Here, we have isolated and characterized the Tbx3+ cells from Tbx3+/Venus knock-in mice. We studied electrophysiological parameters during development and fo...

Among lizards, only monitor lizards (Varanidae) have a functionally divided cardiac ventricle. This enables them to sustain higher systemic blood pressures and higher metabolic rates than other reptiles of similar size. The division results from the concerted action of three partial septa, which may have homology to the full ventricular septum of m...

Sustained pacemaker function is a challenge in biological pacemaker engineering. Human cardiomyocyte progenitor cells (CMPCs) have exhibited extended survival in the heart after transplantation. We studied whether lentivirally transduced CMPCs that express the pacemaker current If (encoded by HCN4) can be used as functional gene delivery vehicle in...

The cardiac conduction system (CCS) initiates and coordinately propagates the electrical impulse to orchestrate the heartbeat. It consists of a set of interconnected components with shared properties. A better understanding of the origin and specification of CCS lineages has allowed us to better comprehend the etiology of CCS disease and has provid...

Klebsiella (K.) pneumoniae is a common cause of pneumonia. Previous studies have documented an important role for Toll-like receptors (TLRs) expressed by myeloid cells in the recognition of K. pneumoniae and the initiation of a protective immune response. Lung epithelial cells also express TLRs and can participate in innate immune defense. The aim...

Digital reconstruction of human development The detailed morphology of human development has intrigued scientists and the medical field alike. However, the scarcity of specimens hampers detailed mapping of tissue architecture. Furthermore, inaccuracies in the description of human development have crept into textbooks from observations of animal mod...

Background: Ventricular noncompaction is characterized by excessive trabeculations and is associated with heart failure. The lesion is hypothesized to result from failed compaction and thus retention of embryonic trabeculations. Here, we assess for the first time the identity of trabeculations in noncompaction to test whether noncompacted hearts s...

Numerous signals drive the proliferative expansion of the distal endoderm and the underlying mesenchyme during lung branching morphogenesis, but little is known about how these signals are integrated. Here, we show by analysis of conditional double mutants that the two T-box transcription factor genes Tbx2 and Tbx3 act together in the lung mesenchy...

Background: In human fetuses with cardiac defects and increased nuchal translucency, abnormal ductus venosus flow velocity waveforms are observed. It is unknown whether abnormal ductus venosus flow velocity waveforms in fetuses with increased nuchal translucency are a reflection of altered cardiac function or are caused by local morphological alte...

The cardiac conduction system (CCS) consists of distinctive components that initiate and conduct the electrical impulse required for the coordinated contraction of the cardiac chambers. The development of the CCS involves complex regulatory networks of transcription factors that act in stage, tissue and dosedependent manners. As disrupted function...

The epicardium, the outermost layer of the heart, is an essential source of cells and signals for the formation of the cardiac fibrous skeleton and the coronary vasculature, and for the maturation of the myocardium during embryonic development. The molecular factors that control epicardial mobilization and differentiation, and direct the epicardial...

RT-PCR primer and conditions. The listed RT-PCR primer and conditions were used for qualitative RT-PCR experiments. (XLSX)

Absence of TBX18 and TBX2 protein in mutant embryos. (A) Immunofluorescence analysis of TBX18 on transverse E10.5 sections through right ventricles of control and Tbx18GFP/GFP mice. Epicardial and pericardial cells express TBX18 in the control (white arrows) but not in Tbx18GFP/GFP mice. (B) Immunofluorescence analysis of TBX2 on transverse E10.5 s...

Increase of NOTCH3+-epicardial cells in Tbx18-null mice is independent from Tbx2 or Tbx20. In order to quantify NOTCH3-expressing epicardial cells, immunofluorescent stainings against NOTCH3 were analyzed. (A) Quantification of NOTCH3-positive epicardial cells in Tbx18cre/GFP;Tbx2fl/fl (70.0±4.4%), Tbx18cre/GFP;Tbx2fl/+ (67.9±8.2%), Tbx18cre/+;Tbx2...

Normal fate of epicardium-derived cells in Tbx18cre/+;R26mTmG/+;HprtCAG::TBX2/y mice. Epicardial cells stained for the lineage label GFP enter the myocardium of Tbx18cre/+;R26mTmG/+;HprtCAG::TBX2/y hearts as in Tbx18cre/+;R26mTmG/+;Hprt+/+ controls and contribute to coronary SMCs as indicated by double-immunofluorescence staining against the SMC ma...

Myh11 expression in coronary arteries is unchanged in Tbx18- and Tbx2-deficient hearts at E18.5. (A) In situ hybridization analysis of Myh11 expression on transverse sections of hearts of control, Tbx18GFP/GFP and Tbx18cre/+;Tbx2fl/fl;R26mTmG/+ mice at E18.5. As in control hearts, SMCs of the coronary arteries of both mutant hearts show Myh11 expre...

Objective: To perform a morphological evaluation of the ductus venosus, heart and jugular lymphatic sac (JLS) in first-trimester human fetuses with normal and abnormal ductus venosus flow velocity waveforms (DV-FVWs) and normal and increased nuchal translucency (NT). Method: Postmortem examination was performed on fetuses with increased NT or st...

The paralogous genesNppaandNppbare organized in an evolutionary conserved cluster and are a valuable model to study coregulation and regulatory landscape organization during heart development and disease. Here, we analyzed the chromatin conformation, epigenetic status and enhancer potential of sequences of theNppa-Nppbclusterin vivo Our data indica...

The cardiac conduction system (CCS) consists of distinctive components that initiate and conduct the electrical impulse required for the coordinated contraction of the cardiac chambers. CCS development involves complex regulatory networks that act in stage-, tissue- and dose-dependent manners, and recent findings indicate that the activity of these...

Regulatory DNA elements, short genomic segments that regulate gene expression, have been implicated in developmental disorders and human disease. Despite this clinical urgency, only a small fraction of the regulatory DNA repertoire has been confirmed through reporter gene assays. The overall success rate of functional validation of candidate regula...

To assess whether cardiac failure, due to cardiac defects, and abnormal jugular lymphatic development are involved in nuchal edema (NE) - the morphological equivalent of increased nuchal translucency - in various euploid mutant mouse models. Mouse embryos with lymphatic abnormalities and NE (Ccbe1(-/-) ), with cardiac defects and NE (Fkbp12(-/-) ,...

Heart progenitor cells differentiate into various cell types including pacemaker and working cardiomyocytes. Cell-type specific gene expression is achieved by combinatorial interactions between tissue-specific transcription factors (TFs), co-factors, and chromatin remodelers and DNA binding elements in regulatory regions. Dysfunction of these trans...

This overview provides insight into the underlying genetic mechanism of the high incidence of cardiac defects in fetuses with increased nuchal translucency (NT). Nuchal edema, the morphological equivalent of increased NT, is likely to result from abnormal lymphatic development and is strongly related to cardiac defects. The underlying genetic pathw...

Objective Increased nuchal translucency (NT) origins from disturbed lymphatic development. Abnormal neural crest cell (NCC) migration may be involved in lymphatic development. Because both neuronal and lymphatic development share retinoic acid (RA) as a common factor, this study investigated the involvement of NCCs and RA in specific steps in lymph...

Rationale: Proper patterning of the atrioventricular canal (AVC) is essential for delay of electrical impulses between atria and ventricles, and defects in AVC maturation can result in congenital heart disease. Objective: To determine the role of canonical Wnt signaling in the myocardium during AVC development. Methods and results: We used a n...

Atrial septal defect (ASD) is the most common congenital heart defect clinically characterized by an opening in the atrial septum. Mutations in GATA4, TBX5, and NKX2-5 underlie this phenotype. Here, we report on the identification of a novel -6 G > C mutation in the highly conserved Kozak sequence in the 5'UTR of GATA4 in a small family presenting...

Insights into the mechanisms of development of the mammalian four‐chambered heart are based on biological observations at organ, tissue, cell, and molecular levels, but the full integration of these experimental data awaits a systems biology approach. Such an approach can be employed to formulate and test conceptual models in a computational simula...

The transcriptional repressor Tbx3 is involved in lineage specification in several tissues during embryonic development. Germ-line mutations in the Tbx3 gene give rise to Ulnar-Mammary Syndrome (comprising reduced breast development) and Tbx3 is required for mammary epithelial cell identity in the embryo. Notably Tbx3 has been implicated in breast...

Rationale: Cardiac progenitor cells from the second heart field (SHF) contribute to rapid growth of the embryonic heart, giving rise to right ventricular and outflow tract (OFT) myocardium at the arterial pole of the heart, and atrial myocardium at the venous pole. Recent clonal analysis and cell-tracing experiments indicate that a common progenit...

Rationale: The evolutionary conserved Tbx3/Tbx5 gene cluster encodes T-box transcription factors that play crucial roles in the development and homeostasis of the cardiac conduction system in human and mouse. Both genes are expressed in overlapping patterns and function in strictly tissue-specific and dose-dependent manners, yet, their regulation...

Unlabelled: ChIP-seq has become a major tool for the genome-wide identification of transcription factor binding or histone modification sites. Most peak-calling algorithms require input control datasets to model the occurrence of background reads to account for local sequencing and GC bias. However, the GC-content of reads in Input-seq datasets de...

Variations and mutations in the human genome, such as 22q11.2 microdeletion, can increase the risk for congenital defects, including aortic arch malformations. Animal models are increasingly expanding our molecular and genetic insights into aortic arch development. However, in order to justify animal-to-human extrapolations, a human morphological,...

The sinus venosus, the cardiac chamber upstream of the (right) atrium, is a severely underinvestigated structure. Yet, its myocardium harbors the cardiac pacemaker in all vertebrates. In human, ectopic pacemaking and subsequent pathologies may originate from sinus venosus-derived myocardium surrounding the coronary sinus and the superior caval vein...

Background: The PR interval on the ECG reflects atrial depolarization and atrioventricular nodal delay which can be partially differentiated by P wave duration and PR segment, respectively. Genome-wide association studies have identified several genetic loci for PR interval, but it remains to be determined whether this is driven by P wave duration...

The embryonic vertebrate heart tube develops an atrioventricular canal that divides the atrial and ventricular chambers, forms atrioventricular conduction tissue and organizes valve development. Here we assess the transcriptional mechanism underlying this localized differentiation process. We show that atrioventricular canal-specific enhancers are...

Variants in SCN10A, which encodes a voltage-gated sodium channel, are associated with alterations of cardiac conduction parameters and the cardiac rhythm disorder Brugada syndrome; however, it is unclear how SCN10A variants promote dysfunctional cardiac conduction. Here we showed by high-resolution 4C-seq analysis of the Scn10a-Scn5a locus in murin...

The Brugada syndrome (BrS) is considered a rare mendelian disorder with autosomal dominant transmission. BrS is associated with an increased risk of sudden cardiac death and specific ECG features consisting of ST-segment elevation in the right precordial leads. Loss-of-function mutations in SCN5A, encoding the pore-forming subunit of the cardiac so...

The expression of Nppa (ANF) and Nppb (BNP) marks chamber myocardium in the embryo, and both genes serve as early and accurate markers for hypertrophy and heart failure. Non-invasive visualization of Nppa/Nppb expression in living mice would enable to evaluate the disease state during the course of time in heart disease models. We sought to develop...

Owing to its intrinsic beauty and biomedical importance, the heart has been the focus of intensive research. The recent EMBO/EMBL-sponsored symposium 'Cardiac Biology: From Development to Regeneration' gathered cardiovascular scientists from across the globe to discuss the latest advances in our understanding of the development and growth of the he...

The inaugural Kjell Johansen lecture in the Zoophysiology Department of Aarhus University (Aarhus, Denmark), afforded the opportunity for a focused workshop comprising comparative cardiovascular physiologists to ponder some of the key unanswered questions in the field. Discussions were centered around three themes. The first considered function of...

The coordinated contraction of the heart relies on the generation and conduction of the electrical impulse. Aberrations of the function of the cardiac conduction system have been associated with various arrhythmogenic disorders and increased risk of sudden cardiac death. The genetics underlying conduction system function have been investigated usin...

The homeobox transcription factor Pitx2 displays a highly specific expression pattern during embryogenesis. Gain and loss of function experiments have unraveled its pivotal role in left-right signaling. Conditional deletion in mice has demonstrated a complex and intricate role for Pitx2 in distinct aspects of cardiac development and more recently a...

Brugada syndrome is a rare cardiac arrhythmia disorder, causally related to SCN5A mutations in around 20% of cases. Through a genome-wide association study of 312 individuals with Brugada syndrome and 1,115 controls, we detected 2 significant association signals at the SCN10A locus (rs10428132) and near the HEY2 gene (rs9388451). Independent replic...

The mammalian heart expresses two closely related natriuretic peptide (NP) hormones, atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP). The excretion of the NPs and the expression of their genes strongly respond to a variety of cardiovascular disorders. NPs act to increase natriuresis and decrease vascular resistance, thereby decr...

Tbx2 and Tbx3 are two highly related members of the T-box transcription factor gene family that regulate patterning and differentiation of a number of tissue rudiments in the mouse. Both genes are partially co-expressed in the ventral diencephalon and the infundibulum; however, a functional requirement in murine pituitary development has not been r...

Rationale: In patients with Brugada syndrome, arrhythmias typically originate in the right ventricular outflow tract (RVOT). The RVOT develops from the slowly conducting embryonic outflow tract. Objective: We hypothesize that this embryonic phenotype is maintained in the fetal and adult RVOT and leads to conduction slowing, especially after sodi...

Objective: Velopharyngeal hypotonia seems to be an important factor in velopharyngeal dysfunction in 22q11.2 deletion syndrome, but the etiology is not understood. Because TBX1 maps within the typical 22q11.2 deletion and Tbx1-deficient mice phenocopy many findings in patients with the 22q11.2 deletion syndrome, TBX1 is considered the major candid...

Tbx2 and Tbx3 exhibit dynamic expression in the developing mouse limb bud. Comparative expression analysis of Tbx2 and Tbx3 in whole forelimb (A–F) and hindlimb buds (G–L) of wild-type mouse embryos by in situ hybridization. Probes used and embryonic stages are indicated in the figure. At the posterior limb bud margin the distal limit of expression...

(A–D) Tbx2 expressing cells contribute to posterior digits 3, 4 and 5. (A, B) X-Gal stainings to detect ß-galactosidase activity in E13.0 Tbx2cre/+;R26lacZ/+ fore- and hindlimbs. Cells previously expressing Tbx2 as detected by β-galactosidase activity are present in the anterior and posterior flank mesenchyme and in the posterior half of the autopo...

(A–C) Expression analysis of the Bmp target genes Dkk1, Msx1 and Msx2 by whole mount in situ hybridization in E11.5 wild-type and Tbx2−/− hindlimbs. Magnified regions (1 and 2) in (A) show loss of mesenchymal Dkk1 expression in the posterior limb bud region (arrow) of Tbx2−/− mutants but maintained expression in the adjacent AER (asterisks). (B–C)...

TBX2 protein levels and apoptosis in misexpression embryos. (A, B) Analysis of endogenous Tbx2 and transgenic TBX2 protein expression. Anterior and posterior halves of E11.5 forelimbs were collected (as shown in the scheme in A), and lysates were analyzed by Western blot. TBX2 misexpression in Prrx1-TBX2 (Prrx1-cre/+;HprtTBX2/Y) embryos was found a...

Selective disruption of posterior e-m signaling following TBX2 misexpression in the limb. (A–F) In situ hybridization analysis of Spry4, Ptch1, Fgf9, Fgf17, Fgf8 and Etv4 expression in E10.5 wild-type and Prrx1-TBX2 (Prrx1-cre/+;HprtTBX2/Y) forelimbs. Spry4, Ptch1, Fgf9 and Fgf17 are strongly reduced (red arrowheads) following TBX2 misexpression, w...

Author Summary Developmental defects of the limb skeleton, such as variations from the normal number of digits, can result from an abnormal size of the early limb bud. The mechanisms that restrict limb bud growth to avoid polydactyly, i.e. the formation of extra digits, are unclear. Gremlin 1 (Grem1) has been identified as a key regulator in this p...

ChIP-seq is rapidly becoming a routine technique for the determination of the genome wide association of DNA binding proteins and histone modifications. Here we provide a protocol for the isolation, purification, and immunoprecipitation of DNA fragments associated with a target transcription factor of interest. Although the method makes use of adul...

Identification and verification of novel transcription factor interactions is an inherent step in the discovery of molecular mechanisms driving gene transcription and regulation. Co-immunoprecipitation and GST-pull down are often key techniques in the verification process. Despite wide applicability, their use may sometimes be restricted. We provid...

Author Summary During organ formation, proliferation rates and differentiation patterns vary widely between different stages and tissue compartments. It is poorly understood how cell cycle progression is locally controlled and integrated with patterning processes in these developmental programs. Here, we used the mouse lung as a model to study how...

Vertebrate organ development relies on the precise spatiotemporal orchestration of proliferation rates and differentiation patterns in adjacent tissue compartments. The underlying integration of patterning and cell cycle control during organogenesis is insufficiently understood. Here, we have investigated the function of the patterning T-box transc...

Quantification of Tbx2/TBX2 protein in TBX2-overexpressing lungs by Western blot analysis. 4 lungs each of E18.5 control and Tbx2cre/+;HprtTBX2/+ embryos were pooled and lysed in 1 ml of Nonidet-P40 buffer. After sonification, 2 µl of the lysate (1∶500) and 0.2 µl (1∶5000), respectively, were loaded on the gel and analyzed with an anti-Tbx2 antibod...

Branching morphogenesis is not affected in explant cultures of Tbx2cre/+;HprtTBX2/+ lungs. (A) Morphology of lung explants from E12.0 wildtype and Tbx2cre/+;HprtTBX2/+ embryos at the start and after 6 days of culture. Boxes show regions that were magnified to see branching endpoints in the lower panel. (B) Quantitative and statistical analysis of b...

Normal epithelial differentiation in P40 Tbx2cre/+;HprtTBX2/+ mice. Immunofluorescence (Tagln) and immunohistochemistry (Emcn, Sox2, Sox9, Tubb4a, Scgb1a1, Aqp5, Pdpn, Sftpc1) on frontal section of wildtype (wt) and TBX2-overexpressing (Tbx2cre/+;HprtTBX2/+) lungs for endothelial cells (Emcn), for smooth muscle cells surrounding the proximal airway...

Endogenous Tbx2/TBX2 represses endogenous Cdkn1b in B16 melanoma and MCF-7 breast cancer cell lines. Immunofluorescent stainings of TBX2/Tbx2 and CDKN1B/Cdkn1b protein in human MCF-7 (human) and mouse B16 cell lines transfected with siRNA specific for TBX2/Tbx2 or a non-silencing control siRNA. Knock-down of TBX2/Tbx2 results in upregulation of CDK...

Statistical analyses of morphological, cellular and molecular changes in lungs with loss or gain of Tbx2 activity. (PDF)

Primers and conditions for analysis of expression by semi-quantitative RT-PCR. (PDF)

Primers and conditions of PCRs for genotyping of mouse strains. (PDF)

Perturbations in cardiac development result in congenital heart disease, the leading cause of birth defect-related infant morbidity and mortality. Advances in cardiac developmental biology have significantly augmented our understanding of signalling pathways and transcriptional networks underlying heart formation. Cardiogenesis is initiated with th...

The heart is a structurally complex and functionally heterogeneous organ. The repertoire of genes active in a given cardiac cell defines its shapes and function. This process of localized or heterogeneous gene expression is regulated to a large extent at the level of transcription, dictating the degree particular genes in a cell are active. Therefo...

NKX2-5 is a homeodomain-containing transcription factor implied in both heart and thyroid development. Numerous mutations in NKX2-5 have been reported in individuals with congenital heart disease (CHD), but recently a select few have been associated with thyroid dysgenesis, among which the p.A119S variation. We sequenced NKX2-5 in 303 sporadic CHD...

Rationale: The Slit-Roundabout (Robo) signaling pathway has pleiotropic functions during Drosophila heart development. However, its role in mammalian heart development is largely unknown. Objective: To analyze the role of Slit-Robo signaling in the formation of the pericardium and the systemic venous return in the murine heart. Methods and resu...

In the mammalian heart a conduction system of nodes and conducting cells generates and transduces the electrical signals evoking myocardial contractions. Specialized pacemaker cells initiating and controlling cardiac contraction rhythmicity are localized in an anatomically identifiable structure of myocardial origin, the sinus node. We previously s...

Generation of a reporter transgenic line for isl1. (A) An expression cassette containing the GalFF gene [42] and kanamycin resistance gene was inserted by recombineering into BAC CH211-219F7 at the ATG site of the 1st exon of the isl1 gene. The site of recombineering is approximately 40 kb inside the BAC sequence, minimizing any risk of loss of isl...

Recording of the heart beating of an isl1−/− embryo at 2 dpf. Ventral view (anterior to the left). Note the reduced speed of the contractions and their irregularity (also see Fig.1B). Playback speed (150 fps) is set to match recording speed to render natural speed of the embryo's heart beat. (AVI)

Expression of tbx2b at the venous pole in embryonic heart. Expression patterns by mRNA in situ hybridization of tbx2b and nppa in 2 dpf embryos. Expression of tbx2b at the venous pole (blue staining indicated with arrowheads) does not overlap with nppa expression (red staining), which is confined to atrium and ventricle chamber myocardium. Pictures...

Isl1 expression in the sinus node of the adult mouse heart. (A) 4-chamber view of section through adult wild-type mouse heart. Boxed region indicates the region shown enlarged in (B). (B) Expression of Isl1, depicted in red, colocalizes with the expression of the sinus node marker Hcn4, depicted in green. Dotted line in (B) demarcates the sinus nod...

Isl1BAC reporter activity in adult heart. Confocal images of Tg(isl1BAC:GalFF; UAS:RFP; myl7:eGFP) after immunolabeling with anti-RFP and anti-GFP antibodies (A), or Tg(isl1BAC:GalFF; UAS:GFP) after immunolabeling with anti-GFP and antitropomyosin antibodies (B). Isl1 expressing cells (indicated with arrows) are located at the base of the venous va...

Immunohistochemical detection of Islet-1 in human cardiomyocytes in the sinoatrial node. (A) Hematoxylin and eosin staining of the sinoatrial node. SN indicates the area of the node showing where the specialized cardiomyocytes are located. MC indicates myocardium adjacent to the node. NA indicates the nodal artery. The boundary between SN and MC is...

Recording of the heart beating of an isl1 sibling embryo at 2 dpf. Ventral view (anterior to the left). Note the speed and regularity of the contractions (also see Fig.1B). Playback speed (150 fps) is set to match recording speed to render natural speed of the embryo's heart beat. (AVI)

Early cardiac development involves the formation of a heart tube, looping of the tube and formation of chambers. These processes are highly similar among all vertebrates, which suggest the existence of evolutionary conservation of the building plan of the heart. From the jawless lampreys to man, T-box transcription factors like Tbx5 and Tbx20 are f...

At the end of the first week of mouse gestation, cardiomyocyte differentiation initiates in the cardiac crescent to give rise to the linear heart tube. The heart tube subsequently elongates by addition of cardiac progenitor cells from adjacent pharyngeal mesoderm to the growing arterial and venous poles. These progenitor cells, termed the second he...

Aims Transgenic mice are frequently used to investigate the role of genes involved in cardiac conduction. The QRS duration calculated from the electrocardiogram (ECG) is a commonly used measure for ventricular conduction time. However, the relation between ventricular activation and QRS duration calculated from a mouse surface ECG is not well under...

The endothermic state of mammals and birds requires high heart rates to accommodate the high rates of oxygen consumption. These high heart rates are driven by very similar conduction systems consisting of an atrioventricular node that slows the electrical impulse and a His-Purkinje system that efficiently activates the ventricular chambers. While e...

The pleuropericardial membranes are fibro-serous walls that separate the pericardial and pleural cavities and anchor the heart inside the mediastinum. Partial or complete absence of pleuropericardial membranes is a rare human disease, the etiology of which is poorly understood. As an attempt to better understand these defects, we wished to analyze...

Tbx18 expression in and around the sinuatrial ridges in Wt1-mutant hearts. (A–D) In situ hybridization analysis of Wt1 expression on sagittal sections trough the venous pole region of control and Wt1-deficient hearts at E11.5 and E13.0. Genotypes and stages are as indicated. Green arrowheads point to the mesenchymal ridges that are also established...

Pericardial defects in Wt1-deficient hearts. (A–H) Histological analysis by haematoxylin and eosin stainings on transverse sections through the PPCs of control (genotype: Wt1+/−) and Wt1-deficient embryos from E11.5 to E14.5. (I–L) In situ hybridization analysis of Tbx18 expression on transverse sections trough the venous pole region of control and...

Insufficient closure of the PPCs in Tbx18-mutant embryos. (A–J) Histological analysis by haematoxylin and eosin staining was performed on sagittal sections of E11.5 to E14.5 control (upper row) and Tbx18-deficient (lower row) hearts as indicated. Arrows highlight the remaining PPCs in Tbx18-deficient embryos. Green arrowheads mark the sinuatrial ri...