CCBE1 is required for coronary vessel development and proper coronary artery stem formation in the mouse heart.

BACKGROUND: Proper coronary vasculature development is essential for late-embryonic and adult heart function. The developmental regulation of coronary embryogenesis is complex and includes the coordinated activity of multiple signaling pathways. CCBE1 plays an important role during lymphangiogenesis, enhancing VEGF-C signaling, which is also required for coronary vasculature formation. However, whether CCBE1 plays a similar role during coronary vasculature development is still unknown. Here, we investigate the coronary vasculature development in Ccbe1 mutant embryos. RESULTS: We show that Ccbe1 is expressed in the epicardium, like Vegf-c, and also in the sinus venosus (SV) at the stages of its contribution to coronary vasculature formation. We also report that absence of CCBE1 in cardiac tissue inhibited coronary growth that sprouts from the SV endocardium at the dorsal cardiac wall. This disruption of coronary formation correlates with abnormal processing of VEGF-C propeptides, suggesting VEGF-C-dependent signaling alteration. Moreover, Ccbe1 loss-of-function leads to the development of defective dorsal and ventral intramyocardial vessels. We also demonstrate that Ccbe1 mutants display delayed and mispatterned coronary artery (CA) stem formation. CONCLUSIONS: CCBE1 is essential for coronary vessel formation, independent of their embryonic origin, and is also necessary for peritruncal vessel growth and proper CA stem patterning. Developmental Dynamics 247:1135-1145, 2018. © 2018 Wiley Periodicals, Inc.

Functional study of DAND5 variant in patients with Congenital Heart Disease and laterality defects.

BACKGROUND: Perturbations on the Left-Right axis establishment lead to laterality defects, with frequently associated Congenital Heart Diseases (CHDs). Indeed, in the last decade, it has been reported that the etiology of isolated cases of CHDs or cases of laterality defects with associated CHDs is linked with variants of genes involved in the Nodal signaling pathway. METHODS: With this in mind, we analyzed a cohort of 38 unrelated patients with Congenital Heart Defects that can arise from initial perturbations in the formation of the Left-Right axis and 40 unrelated ethnically matched healthy individuals as a control population. Genomic DNA was extracted from buccal epithelial cells, and variants screening was performed by PCR and direct sequencing. A Nodal-dependent luciferase assay was conducted in order to determine the functional effect of the variant found. RESULTS: In this work, we report two patients with a DAND5 heterozygous non-synonymous variant (c.455G > A) in the functional domain of the DAND5 protein (p.R152H), a master regulator of Nodal signaling. Patient 1 presents left isomerism, ventricular septal defect with overriding aorta and pulmonary atresia, while patient 2 presents ventricular septal defect with overriding aorta, right ventricular hypertrophy and pulmonary atresia (a case of extreme tetralogy of Fallot phenotype). The functional analysis assay showed a significant decrease in the activity of this variant protein when compared to its wild-type counterpart. CONCLUSION: Altogether, our results provide new insight into the molecular mechanism of the laterality defects and related CHDs, priming for the first time DAND5 as one of multiple candidate determinants for CHDs in humans.

Gene-Edited Human-Induced Pluripotent Stem Cell Lines to Elucidate DAND5 Function throughout Cardiac Differentiation.

(1) Background: The contribution of gene-specific variants for congenital heart disease, one of the most common congenital disabilities, is still far from our complete understanding. Here, we applied a disease model using human-induced pluripotent stem cells (hiPSCs) to evaluate the function of DAND5 on human cardiomyocyte (CM) differentiation and proliferation. (2) Methods: Taking advantage of our DAND5 patient-derived iPSC line, we used CRISPR-Cas9 gene-editing to generate a set of isogenic hiPSCs (DAND5-corrected and DAND5 full-mutant). The hiPSCs were differentiated into CMs, and RT-qPCR and immunofluorescence profiled the expression of cardiac markers. Cardiomyocyte proliferation was analysed by flow cytometry. Furthermore, we used a multi-electrode array (MEA) to study the functional electrophysiology of DAND5 hiPSC-CMs. (3) Results: The results indicated that hiPSC-CM proliferation is affected by DAND5 levels. Cardiomyocytes derived from a DAND5 full-mutant hiPSC line are more proliferative when compared with gene-corrected hiPSC-CMs. Moreover, parallel cardiac differentiations showed a differential cardiac gene expression profile, with upregulated cardiac progenitor markers in DAND5-KO hiPSC-CMs. Microelectrode array (MEA) measurements demonstrated that DAND5-KO hiPSC-CMs showed prolonged field potential duration and increased spontaneous beating rates. In addition, conduction velocity is reduced in the monolayers of hiPSC-CMs with full-mutant genotype. (4) Conclusions: The absence of DAND5 sustains the proliferation of hiPSC-CMs, which alters their electrophysiological maturation properties. These results using DAND5 hiPSC-CMs consolidate the findings of the in vitro and in vivo mouse models, now in a translational perspective. Altogether, the data will help elucidate the molecular mechanism underlying this human heart disease and potentiates new therapies for treating adult CHD.

Depletion of DAND5 Hinders EMT in Mouse Embryonic Stem Cell Differentiation.

BACKGROUND: Dand5 encodes a protein that acts as an antagonist to Nodal/TGF-ß and Wnt pathways. A mouse knockout (KO) model has shown that this molecule is associated with left-right asymmetry and cardiac development, with its depletion causing heterotaxia and cardiac hyperplasia. OBJECTIVE: This study aimed to investigate the molecular mechanisms affected by the depletion of Dand5. METHODS: DAND5-KO and wild-type embryoid bodies (EBs) were used to assess genetic expression with RNA sequencing. To complement the expression results that pointed towards differences in epithelial to mesenchymal transition (EMT), we evaluated migration and cell attachment. Lastly, in vivo valve development was investigated, as it was an established model of EMT. RESULTS: DAND5-KO EBs progress faster through differentiation. The differences in expression will lead to differences in the expression of genes involved with Notch and Wnt signalling pathways, as well as changes in the expression of genes encoding membrane proteins. Such changes were accompanied by lower migratory rates in DAND5-KO EBs, as well as higher concentrations of focal adhesions. Within valve development, Dand5 is expressed in the myocardium underlying future valve sites, and its depletion compromises correct valve structure. CONCLUSION: The DAND5 range of action goes beyond early development. Its absence leads to significantly different expression patterns in vitro and defects in EMT and migration. These results have an in vivo translation in mouse heart valve development. Knowledge regarding the influence of DAND5 in EMT and cell transformation allows further understanding of its role in development, or even in some disease contexts, such as congenital heart defects.

CCBE1 in Cardiac Development and Disease.

The collagen- and calcium-binding EGF-like domains 1 (CCBE1) is a secreted protein extensively described as indispensable for lymphangiogenesis during development enhancing VEGF-C signaling. In human patients, mutations in CCBE1 have been found to cause Hennekam syndrome, an inherited disease characterized by malformation of the lymphatic system that presents a wide variety of symptoms such as primary lymphedema, lymphangiectasia, and heart defects. Importantly, over the last decade, an essential role for CCBE1 during heart development is being uncovered. In mice, Ccbe1 expression was initially detected in distinct cardiac progenitors such as first and second heart field, and the proepicardium. More recently, Ccbe1 expression was identified in the epicardium and sinus venosus (SV) myocardium at E11.5-E13.5, the stage when SV endocardium-derived (VEGF-C dependent) coronary vessels start to form. Concordantly, CCBE1 is required for the correct formation of the coronary vessels and the coronary artery stem in the mouse. Additionally, Ccbe1 was found to be enriched in mouse embryonic stem cells (ESC) and revealed as a new essential gene for the differentiation of ESC-derived early cardiac precursor cell lineages. Here, we bring an up-to-date review on the role of CCBE1 in cardiac development, function, and human disease implications. Finally, we envisage the potential of this molecule's functions from a regenerative medicine perspective, particularly novel therapeutic strategies for heart disease.

A novel biallelic loss-of-function variant in DAND5 causes heterotaxy syndrome.

The majority of heterotaxy cases do not obtain a molecular diagnosis, although pathogenic variants in more than 50 genes are known to cause heterotaxy. A heterozygous missense variant in DAND5, a nodal inhibitor, which functions in early development for establishment of right-left patterning, has been implicated in heterotaxy. Recently, the first case was reported of a DAND5 biallelic loss-of-function (LoF) variant in an individual with heterotaxy. Here, we describe a second unrelated individual with heterotaxy syndrome and a homozygous frameshift variant in DAND5 (NM_152654.2:c.197del [p.Leu66ArgfsTer22]). Using an in vitro assay, we demonstrate that the DAND5 c.197del variant is unable to inhibit nodal signaling when compared with the wild-type expression construct. This work strengthens the genetic and functional evidence for biallelic LoF variants in DAND5 causing an autosomal recessive heterotaxy syndrome.

Canonical Wnt signaling and its antagonist regulate anterior-posterior axis polarization by guiding cell migration in mouse visceral endoderm.

The mouse embryonic axis is initially formed with a proximal-distal orientation followed by subsequent conversion to a prospective anterior-posterior (A-P) polarity with directional migration of visceral endoderm cells. Importantly, Otx2, a homeobox gene, is essential to this developmental process. However, the genetic regulatory mechanism governing axis conversion is poorly understood. Here, defective axis conversion due to Otx2 deficiency can be rescued by expression of Dkk1, a Wnt antagonist, or following removal of one copy of the beta-catenin gene. Misexpression of a canonical Wnt ligand can also inhibit correct A-P axis rotation. Moreover, asymmetrical distribution of beta-catenin localization is impaired in the Otx2-deficient and Wnt-misexpressing visceral endoderm. Concurrently, canonical Wnt and Dkk1 function as repulsive and attractive guidance cues, respectively, in the migration of visceral endoderm cells. We propose that Wnt/beta-catenin signaling mediates A-P axis polarization by guiding cell migration toward the prospective anterior in the pregastrula mouse embryo.

Generation of a gene-corrected human induced pluripotent stem cell line derived from a patient with laterality defects and congenital heart anomalies with a c.455G > A alteration in DAND5.

Human induced pluripotent stem cells (hiPSCs) from individual patient basis are considered a powerful resource to model human diseases. However, to study complex multigenic diseases such as Congenital Heart Disease, it is crucial to generate perfect isogenic controls to understand gene singularity and contribution. Here, we report the engendering of an isogenic hiPSC line with homozygous correction of c.455G > A alteration in the DAND5 gene, using CRISPR/Cas9 technology. The characterization of a clone of this cell line demonstrates normal karyotype, pluripotent state, and potential to differentiate in vitro towards endoderm, mesoderm, and ectoderm.

Full-length human CCBE1 production and purification: leveraging bioprocess development for high quality glycosylation attributes and functionality.

Collagen and calcium-binding EGF domain-1 (CCBE1) is a secreted protein critical for lymphatic/cardiac vascular development and regeneration. However, the low efficient production of the recombinant full-length CCBE1 (rCCBE1) has been a setback for functional studies and therapeutic applications using this protein. The main goal of this work was to implement a robust bioprocess for efficient production of glycosylated rCCBE1. Different bioprocess strategies were combined with proteomic tools for process/product characterization, evaluating the impact of process parameters on cell performance, rCCBE1 production and quality. We have shown that rCCBE1 volumetric yield was positively correlated with higher cell density at transfection (HDT), and under these conditions the secreted protein presented a mature glycosylated profile (complex N-glycans). Mild hypothermia was also applied to HDT condition that resulted in enhanced cell viability; however an enrichment of immature rCCBE1 variants was detected. Mass spectrometry-based tools allowed the identification of rCCBE1 peptides confirming protein identity in the affinity chromatography enriched product. rCCBE1 biological activity was validated by in vitro angiogenesis assay, where enhanced vessel formation was observed. Herein, we report a step forward in the production and characterization of human glycosylated rCCBE1, amenable for in vitro and in vivo studies to explore its regenerative therapeutic potential.

Generation and characterization of a human iPS cell line from a patient-related control to study disease mechanisms associated with DAND5 p.R152H alteration.

A DAND5-control human iPSC line was generated from the urinary cells of a phenotypically normal donor. Exfoliated renal epithelial (RE) cells were collected and reprogrammed into iPSCs using Sendai virus reprogramming system. The pluripotency, in vitro differentiation potential, karyotype stability, and the transgene-free status of generated iPSC line were analyzed and confirmed. This cell line can be exploited as a control iPSC line to better understand the mechanisms involved in DAND5-associated cardiac disease.

The anterior-posterior axis emerges respecting the morphology of the mouse embryo that changes and aligns with the uterus before gastrulation.

BACKGROUND: When the anterior-posterior axis of the mouse embryo becomes explicit at gastrulation, it is almost perpendicular to the long uterine axis. This led to the belief that the uterus could play a key role in positioning this future body axis. RESULTS: Here, we demonstrate that when the anterior-posterior axis first emerges it does not respect the axes of the uterus but, rather, the morphology of the embryo. Unexpectedly, the emerging anterior-posterior axis is initially aligned not with the long, but the short axis of the embryo. Then whether the embryo develops in vitro or in utero, the anterior-posterior axis becomes aligned with the long axis of embryo just prior to gastrulation. Of three mechanisms that could account for this apparent shift in anterior-posterior axis orientation-cell migration, spatial change of gene expression, or change in embryo shape-lineage tracing studies favor a shape change accompanied by restriction of the expression domain of anterior markers. This property of the embryo must be modulated by interactions with the uterus as ultimately the anterior-posterior and long axes of the embryo align with the left-right uterine axis. CONCLUSIONS: The emerging anterior-posterior axis relates to embryo morphology rather than that of the uterus. The apparent shift in its orientation to align with the long embryonic axis and with the uterus is associated with a change in embryo shape and a refinement of anterior gene expression pattern. This suggests an interdependence between anterior-posterior gene expression, the shape of the embryo, and the uterus.

Molecular construction of bionanoparticles: chimaeric SIV p17-HIV I p6 nanoparticles with minimal viral protein content.

VLPs (virus-like particles) are promising delivery vectors for molecular therapy, since they combine the major advantages of viral vectors with significantly fewer viral vector disadvantages. The present paper describes the molecular construction of chimaeric VLPs based on minimal SIV (simian immunodeficiency virus) and HIV1 components. A chimaeric protein was constructed by fusion of SIV matrix protein (p17) and HIV1 p6 protein, and we demonstrated that the chimaeric proteins assemble as 80 nm nanoparticles containing approximately 7700 chimaeric protein units. Chimaeric VLPs are released from HEK-293T cells (human embryonic kidney cells expressing the large T-antigen of simian virus 40) and are fully encapsulated with lipid membrane. Chimaeric VLPs are produced at 3.7-fold higher levels when compared with SIV p17 VLPs owing to duplication of a PTAP (Pro-Thr-Ala-Pro) domain previously shown as essential for virus particle release. The chimaeric VLPs constructed in the present paper were efficiently pseudotyped with vesicular-stomatitis-virus glycoprotein, as shown by immunoprecipitation assays.

The Role of Cerl2 in the Establishment of Left-Right Asymmetries during Axis Formation and Heart Development.

The formation of the asymmetric left-right (LR) body axis is one of the fundamental aspects of vertebrate embryonic development, and one still raising passionate discussions among scientists. Although the conserved role of nodal is unquestionable in this process, several of the details around this signaling cascade are still unanswered. To further understand this mechanism, we have been studying Cerberus-like 2 (Cerl2), an inhibitor of Nodal, and its role in the generation of asymmetries in the early vertebrate embryo. The absence of Cerl2 results in a wide spectrum of malformations commonly known as heterotaxia, which comprises defects in either global organ position (e.g., situs inversus totalis), reversed orientation of at least one organ (e.g., situs ambiguus), and mirror images of usually asymmetric paired organs (e.g., left or right isomerisms of the lungs). Moreover, these laterality defects are frequently associated with congenital heart diseases (e.g., transposition of the great arteries, or atrioventricular septal defects). Here, reviewing the knowledge on the establishment of LR asymmetry in mouse embryos, the emerging conclusion is that as necessary as is the activation of the Nodal signaling cascade, the tight control that Cerl2-mediates on Nodal signaling is equally important, and that generates a further regionalized LR genetic program in the proper time and space.

Generation of human iPSC line from a patient with laterality defects and associated congenital heart anomalies carrying a DAND5 missense alteration.

A human iPSC line was generated from exfoliated renal epithelial (ERE) cells of a patient affected with Congenital Heart Disease (CHD) and Laterality Defects carrying tshe variant p.R152H in the DAND5 gene. The transgene-free iPSCs were generated with the human OSKM transcription factor using the Sendai-virus reprogramming system. The established iPSC line had the specific heterozygous alteration, a stable karyotype, expressed pluripotency markers and generated embryoid bodies that can differentiate towards the three germ layers in vitro. This iPSC line offers a useful resource to study the molecular mechanisms of cardiomyocyte proliferation, as well as for drug testing.

Matrix Gla Protein expression pattern in the early avian embryo.

MGP (Matrix Gla Protein) is an extracellular matrix vitamin K dependent protein previously identified as a physiological inhibitor of calcification and shown to be well conserved among vertebrates during evolution. MGP is involved in other mechanisms such as TGF-ß and BMP activity, and a proposed modulator of cell-matrix interactions. MGP is expressed early in vertebrate development although its role has not been clarified. Previous work in the chicken embryo found MGP localization predominantly in the aorta and aortic valve base, but no data is available earlier in development. Here we examined MGP expression pattern using whole-mount in situ hybridization and histological sectioning during the initial stages of chick development. MGP was first detected at HH10 in the head and in the forming dorsal aorta. At the moment of the onset of blood circulation, MGP was expressed additionally in the venous plexus which will remodel into the vitelline arteries. By E2.25, it is clear that the vitelline arteries are MGP positive. MGP expression progresses centrifugally throughout the area vasculosa of the yolk sac. Between stages HH17 and HH19 MGP is seen in the dorsal aorta, heart, notochord, nephric duct, roof plate, vitelline arteries and in the yolk sac, beneath main arterial branches and in the vicinity of several vessels and venules. MGP expression persists in these areas at least until E4.5. These data suggest that MGP expression could be associated with cell migration and differentiation and to the onset of angiogenesis in the developing chick embryo. This data has biomedical relevance by pointing to the potential use of chick embryo explants to study molecules involved in artery calcification.

Identification of alternative promoter usage for the matrix Gla protein gene. Evidence for differential expression during early development in Xenopus laevis.

Recent cloning of the Xenopus laevis (Xl) matrix Gla protein (MGP) gene indicated the presence of a conserved overall structure for this gene between mammals and amphibians but identified an additional 5'-exon, not detected in mammals, flanked by a functional, calcium-sensitive promoter, 3042 bp distant from the ATG initiation codon. DNA sequence analysis identified a second TATA-like DNA motif located at the 3' end of intron 1 and adjacent to the ATG-containing second exon. This putative proximal promoter was found to direct transcription of the luciferase reporter gene in the X. laevis A6 cell line, a result confirmed by subsequent deletion mutant analysis. RT-PCR analysis of XlMGP gene expression during early development identified a different temporal expression of the two transcripts, strongly suggesting differential promoter activation under the control of either maternally inherited or developmentally induced regulatory factors. Our results provide further evidence of the usefulness of nonmammalian model systems to elucidate the complex regulation of MGP gene transcription and raise the possibility that a similar mechanism of regulation may also exist in mammals.

Goosecoid and cerberus-like do not interact during mouse embryogenesis.

Mouse Cerberus-like (Cer-l) is a neural inducer molecule, capable of inhibiting Nodal and BMP-4 signals in the extracelular space. The cer-l expression domain in the Anterior Visceral Endoderm (AVE) and prechordal plate, tissues involved in head induction and patterning, respectively, suggested a role for this gene in head formation. However, animals homozygous for the cer-l null allele failed to show any abnormality, leading us to propose the existence of other factor(s) that might compensate for cer-l loss-of-function. Since goosecoid (gsc) shares some domains of expression with cer-l and was shown to be essential for head morphogenesis, we tested its ability to interact genetically with cer-l. With this aim we generated cer-l;gsc double mutants. These animals were analyzed at birth for skeletal defects and revealed the same phenotype as gsc-/- single mutants. We also investigated the proper patterning of structures adjacent to the prechordal plate by performing in situ hybridization of HNF-3beta, Six-3 and BF-1, genes whose expression domains remained unchanged. In conclusion, the analysis carried out indicated that gsc does not compensate for cer-l loss-of-function and that these genes do not interact genetically.

Expression pattern of zcchc24 during early Xenopus development.

We report the expression pattern of a novel Xenopus laevis gene, zcchc24, which encodes a protein containing two zinc finger domains from the zf-CCHC and zf-3CxxC superfamilies. This protein shares >84% amino acid identity with its vertebrate homologues. During X. laevis embryonic development, zcchc24 is expressed at gastrula stages in the dorsal mesoderm, including the cardiac precursors region. During neurula stages, zcchc24 is expressed as two stripes in the dorsal region, more precisely, in the somitogenic mesoderm until the cardiac mesoderm. At early tailbud stages, zcchc24 continues to be expressed in these regions, but starts to be expressed in the migrating neural crest. Later, this gene is expressed in the head, branchial arches, heart and somites. The zinc finger domains present in Zcchc24 protein and its dynamic gene expression pattern suggest that Zcchc24 might be involved in the regulation of heart, somites and of branchial arch formation/patterning, namely in the regulation of apoptosis.

Identification of differentially expressed genes in the heart precursor cells of the chick embryo.

Genetic evidence has implicated several genes as being critical for heart development. However, the inducers of these genes as well as their targets and pathways they are involved with, remain largely unknown. Previous studies in the avian embryo showed that at HH4 Cerberus (cCer) transcripts are detected in the anterior endomesoderm including the heart precursor cells and later in the left lateral plate mesoderm. We have identified a promoter element of chick cCer able to drive EGFP expression in a population of cells that consistently exit from the anterior primitive streak region, from as early as stage HH3+, and that later will populate the heart. Using this promoter element as a tool allowed us to identify novel genes previously not known to potentially play a role in heart development. In order to identify and study genes expressed and involved in the correct development and differentiation of the vertebrate heart precursor cell (HPC) lineages, a differential screening using Affymetrix GeneChip system technologies was performed. Remarkably, this screening led to the identification of more than 700 transcripts differentially expressed in the heart forming regions (HFR). Bioinformatic tools allowed us to filter the large amount of data generated from this approach and to select a few transcripts for in vivo validation. Whole-mount in situ hybridization and sectioning of selected genes showed heart and vascular expression patterns for these transcripts during early chick development. We have developed an effective strategy to specifically identify genes that are differentially expressed in the HPC lineages. Within this set we have identified several genes that are expressed in the heart, blood and vascular lineages, which are likely to play a role in their development. These genes are potential candidates for future functional studies on early embryonic patterning.