Conotruncus Research Articles

Evolución filogenética del corazón

In 1859 Charles Darwin in his “The Origin of Species” formulated three facts that explain the principle of evolution: the presence of a common ancestor, the existence of advantageous genetic mutations for survival and the elimination of unfavorable ones or Natural Selection. The embryological development of the mammalian heart improves the need for external oxygen uptake, transport and release in the tissues, which exists in all multicellular living beings from the most primitive and enables the function of all organs and systems. In invertebrates, such as insects, arthropods and molluscs, the open circulatory system reaches a development similar to that of human Carnegie stages 10-13: endocardial tubes, straight tube, or early stages of the bulboventricular loop. In vertebrates, the closed system of fish develops hearts with three and four chambers equivalent to the torsion phase of the loop in mammals, or the fifth week of human embryonic development, with a model closer to that of mammals appearing in reptiles with differences such as the incomplete septation of the ventricles and the development of two aortic trunks in crocodilians. Birds and mammals have reached a similar degree of embryonic development of their hearts, with four septate chambers, the same as the Cono Truncus one, and which separate the systemic and pulmonary circulation. All the embryological development of the human heart is completed between days 20 and 60 of gestation, concluding in the fetal phase its growth together with the rest of the organism.

Early Development of the Heart and Great Vessels

The cardiovascular system is one of the first organ systems to develop in the embryo. By day 21, three germ layers: endoderm, mesoderm, and ectoderm are formed by the gastrulation process. Cells in the mesoderm coalesce through a process called vasculogenesis to form two parallel endocardial tubes. Folding of the gut tube brings these two parallel endocardial tubes towards the midline enabling them to fuse into a single linear‐shaped heart tube. By day 18, the lateral plate mesoderm splits to form two layers – splanchnic (visceral) and somatic (parietal). The cells of the splanchnic mesoderm will develop into the myocardial cells of a Primary (PHF) and Secondary Heart field (SHF). By day 22, the heart begins to beat and lengthen by the addition of cells from the SHF to the PHF. This develops into the outflow tract ‐ aortic and pulmonary vessels, and the right ventricle. By day 28, the linear‐shaped heart tube contains regions called the sinus venosus, primitive atrium, primitive ventricle, and bulbus cordis (outflow). The proximal and distal ends become “fixed” by the pericardium, the bulbus cordis and primitive ventricle grow faster than the other regions of the heart tube, and the heart bends upon itself to form a u‐shape. The primitive atrium and sinus venosus are moved dorsally, and the heart begins septation into 4 chambers. As early as day 14, two actively growing ridges called Endocardial Cushion (of the PHF) nearly divide the single lumen into two separate cavities connected by a singular (atrioventricular) canal. Subsequently, a septum grows from the cushions toward the roof of the common atrium, and from the cushions toward the apex of the primitive ventricle. Continued addition of cushion cells to the atrioventricular canal divides a single canal into a left and right canal, as well as valves attached to the ventricular wall by muscular cords. Abnormalities of Endocardial cushion can affect structures derived from the PHF. For example, Tricuspid Atresia involves the malformation of the right Atrioventricular Canal and is associated with: (i) Atrial, and (ii) Ventricular Septal Defect; (iii) hypotrophy of the right ventricle; and (iv) hypertrophy of the left ventricle. Cells of the SHF are involved in the formation and lengthening of the outflow tract. Interestingly, this growth is regulated by neural crest cells. Insults to neural crest cell development or migration can affect structures derived from the PHF. For example, Tetralogy of Fallot involves an unequal division and laterality of the bulbus cordis associated with: (1) narrow right ventricular outflow; (2) interventricular septal defect; (3) over‐riding aorta directly above the septal defect; (4) hypertrophy of the right ventricular wall because of high pressure in the right side of the heart. Neural crest cells also contribute to craniofacial development leading to facial and cardiac abnormalities in the same individual.

P1468 a rare cause of chest pain:sudden rupture of aortic valsalva sinus aneurysm

Abstract Introduction Sinus of Valsalva aneurysms (SOVAs) occur when there is a congenital defect in the aortic media and incomplete fusion of distal bulbar septum (primitive bulbus cordis) and truncal ridges. These aneurysms usually rupture into the right side of the heart, with the right ventricle being the most common. Case Presentation A 32 year old male patient who presented to our facility with an attack of ulcerative colitis activity ,elevated inflammatory markers and thrombocytosis. During hospital stay, he developed sudden onset of retrosternal compressing chest pain. On examination he was afebrile with a blood pressure of 130/80 mm Hg and pulse rate 110 beats per minute. He had soft systolic and early diastolic murmurs with normal chest auscultation; there was no haemodynamic discrepancy between left and right sides or stigmata of endocarditis. His ECG showed sinus rhythm with no ST segment changes, and chest x ray was normal. Full blood count revealed thrombocytosis & normochromic normocytic anemia , cardiac enzymes were normal, blood cultures were sterile. A 2D transthoracic echocardiography (TTE) revealed dilated left ventricular dimensions , there is an aneurysm of the right sinus of Valsalva which is communicating with the right ventricle (RV)confirmed by color Doppler and negative contrast seen inside RV during bubble study. 3D TTE showed a small fistulous track between the right sinus and RV. The patient refused surgical or percutaneous closure. Conclusion Congenital RSVAs account for 0.1–3.5% of congenital heart defects.It has a higher incidence in Asian versus Western populations with male to female ratio 3:1. SOVAs arise from the right sinus of Valsalva in 80–85% of these cases and from the noncoronary sinus in 5–15%. They rarely arise from the left sinus, as the left coronary cusp embryologically is not derived from bulbar septum. This is distinct from acquired SOVAs, which can occur in any of the sinuses Traditionally, surgical closure has been the mainstay of treatment for RSOVAs, with an operative mortality rate of <5% and excellent long-term outcomes. Abstract P1468 Figure. RSOVA

Four-dimensional live imaging of hemodynamics in mammalian embryonic heart with Doppler optical coherence tomography.

Hemodynamic analysis of the mouse embryonic heart is essential for understanding the functional aspects of early cardiogenesis and advancing the research in congenital heart defects. However, high-resolution imaging of cardiac hemodynamics in mammalian models remains challenging, primarily due to the dynamic nature and deep location of the embryonic heart. Here we report four-dimensional micro-scale imaging of blood flow in the early mouse embryonic heart, enabling time-resolved measurement and analysis of flow velocity throughout the heart tube. Our method uses Doppler optical coherence tomography in live mouse embryo culture, and employs a post-processing synchronization approach to reconstruct three-dimensional data over time at a 100 Hz volume rate. Experiments were performed on live mouse embryos at embryonic day 9.0. Our results show blood flow dynamics inside the beating heart, with the capability for quantitative flow velocity assessment in the primitive atrium, atrioventricular and bulboventricular regions, and bulbus cordis. Combined cardiodynamic and hemodynamic analysis indicates this functional imaging method can be utilized to further investigate the mechanical relationship between blood flow dynamics and cardiac wall movement, bringing new possibilities to study biomechanics in early mammalian cardiogenesis. Four-dimensional live hemodynamic imaging of the mouse embryonic heart at embryonic day 9.0 using Doppler optical coherence tomography, showing directional blood flows in the sinus venosus, primitive atrium, atrioventricular region and vitelline vein.

The expression of diacylglycerol kinase theta during the organogenesis of mouse embryos

BackgroundDiacylglycerol kinase (DGK) is a key enzyme that regulates diacylglycerol (DG) turnover and is involved in a variety of physiological functions. The isoform DGKθ has a unique domain structure and is the sole member of type V DGK. To reveal the spatial and temporal expression of DGKθ we performed immunohistochemical staining on paraffin sections of mouse embryos.ResultsAt an early stage of development (E10.5 and 11.5), the expression of DGKθ was prominently detected in the brain, spinal cord, dorsal root ganglion, and limb bud, and was also moderately detected in the bulbus cordis and the primordium of the liver and gut. At later stages (E12.5 and 14.5), DGKθ expression persisted or increased in the neocortex, epithalamus, hypothalamus, medulla oblongata, and pons. DGKθ was also evident in the epidermis, and nearly all epithelia of the oropharyngeal membrane, digestive tract, and bronchea. At prenatal developmental stages (E16.5 and E18.5), the expression pattern of DGKθ was maintained in the central nervous system, intestine, and kidney, but was attenuated in the differentiated epidermis.ConclusionThese results suggest that DGKθ may play important physiological roles not only in the brain, but also in diverse organs and tissues during the embryonic stages.

Rubella virus infection and fetal congenital heart diseases

Objective To investigate the fetal congenital heart diseases (CHD) caused by rubella virus infection, and to explore the methods for prenatal diagnosis of congenital rubella syndrome. Methods The rubella virus-specific IgM of cord blood were tested by ELISA in 38 fetuses with CHD detected by echocardiography after which the pregnancies were terminated. Results Eighteen (47. 4%) out of the 38 fetuses showed IgM( + ) and 20 were IgM( -). The most common seen cardiac abnormalities in the 18 IgM( + ) cases were ventricular septal defect (n = 10), pulmonary artery dysplasia(n = 9), abnormal atrioventricular valves(n = 6), transposition of the great arteries (n = 5) and aortic saddle(n=4). The number of cases with congenital conotruncal defects in IgM( + ) and IgM(-) groups were 11(61.1%) and 5(25.0%), respectively (P<0. 05). Conclusions Rubella virus may influence the development of fetal ventricles and conotruncus. Ultrasound detection of ventricular septal defect, pulmonary artery dysplasia, abnormal heart valves, transposition of the great arteries should alert the clinicians of rubella virus infection. Key words: Heart defects, congenital; Rubivirus infections; Fetal diseases

Repaired tetralogy of Fallot in the adult: monitoring and management

Tetralogy of Fallot (ToF) is the most common cyanotic congenital heart disease (CHD). The history of surgical treatment of ToF is closely linked with the origins of cardiac surgery. Before...

Homozygous Missense N629D hERG (KCNH2) Potassium Channel Mutation Causes Developmental Defects in the Right Ventricle and Its Outflow Tract and Embryonic Lethality

Loss-of-function mutations in the human ERG1 potassium channel (hERG1) frequently underlie the long QT2 (LQT2) syndrome. The role of the ERG potassium channel in cardiac development was elaborated in an in vivo model of a homozygous, loss-of-function LQT2 syndrome mutation. The hERG N629D mutation was introduced into the orthologous mouse gene, mERG, by homologous recombination in mouse embryonic stem cells. Intact homozygous embryos showed abrupt cessation of the heart beat. N629D/N629D embryos die in utero by embryonic day 11.5. Their developmental defects include altered looping architecture, poorly developed bulbus cordis, and distorted aortic sac and branchial arches. N629D/N629D myocytes from embryonic day 9.5 embryos manifested complete loss of I(Kr) function, depolarized resting potential, prolonged action potential duration (LQT), failure to repolarize, and propensity to oscillatory arrhythmias. N629D/N629D myocytes manifest calcium oscillations and increased sarcoplasmic reticulum Ca(+2) content. Although the N629D/N629D protein is synthesized, it is mainly located intracellularly, whereas +/+ mERG protein is mainly in plasmalemma. N629D/N629D embryos show robust apoptosis in craniofacial regions, particularly in the first branchial arch and, to a lesser extent, in the cardiac outflow tract. Because deletion of Hand2 produces apoptosis, in similar regions and with a similar final developmental phenotype, Hand2 expression was evaluated. Robust decrease in Hand2 expression was observed in the secondary heart field in N629D/N629D embryos. In conclusion, loss of I(Kr) function in N629D/N629D cardiovascular system leads to defects in cardiac ontogeny in the first branchial arch, outflow tract, and the right ventricle.

Cardiac Looping and Formation of the Heart Regions in Japanese Quail Embryo (Coturnix coturnix).

In this study the morphological changes of the de- veloping 100 heart tubes and formation of the heart regions in Quail embryos were examined from the first till the fourth day of development. Special dis- secting tools were prepared and used for dissecting the embryos, normal histological techniques for the histological study were adopted and the binocular stereomicroscope, inverted microscope and light microscopes were used. The study proved that the cardiac looping of the Quail embryos, like that of the chick embryos, took 3 stages but occurred earlier: the straight heart tube of the quail was formed at about 24-26 hours of the development. The stage of dextral looping took the period between 26 and 40 hours of the develop- ment. The Transformation of the C-shaped heart loop into the S-shaped heart loop started at 39-40 hours and finished at 52-55 hours of the development. The process of cardiac looping was accompanied by formation of the heart regions and followed by posi- tional changes and disappearance of the Bulbus cordis. The results obtained are important for the embryolo- gists using the quail-chick chimera system in the development. Both quail and chick embryos used in this system must be at the comparable not the same ages of the devel- opment to avoid the malformations resulted from using the miss ages.

Immunohistochemical Observation of Co-expression of E- and N-cadherins in Rat Organogenesis

Cadherins are a family of transmembrane glycoproteins that mediate cell-to-cell adhesion. Isoforms, including E- and N-cadherin, have been identified and shown to regulate morphogenesis through homophilic binding. In the ontogeny, the expressions of E- and N-cadherin change spatiotemporally, and the changes in cadherin isoforms, called cadherin switching, impact the mechanical adhesion of cells. Furthermore, cadherin functions as a receptor that transfers information from outside to inside cells, and in terms of switching, it affects cell phenotypes. To observe the expression patterns of E- and N-cadherins during embryogenesis and to identify cells that transiently coexpress both cadherins, we employed a recently developed immunohistochemical double staining technique in rat fetuses. At embryonic day 9, embryonic ectodermal cells more dominantly expressed E-cadherin, while mesodermal cells more dominantly expressed N-cadherin. At embryonic day 10, the expression pattern of E-cadherin in the surface ectoderm and endoderm and that of N-cadherin in the neuroectoderm were established. After embryonic day 10, unique co-expression of E- and N-cadherin was observed in primordia, such as the bulbus cordis, otic pit, notochord, and Rathke’s pouch. In the present study, it was possible to visualize the expression patterns of E- and N-cadherin during early fetal development, which enabled us to morphologically clarify cadherin switching.

Loss of the Atp2c1 Secretory Pathway Ca2+-ATPase (SPCA1) in Mice Causes Golgi Stress, Apoptosis, and Midgestational Death in Homozygous Embryos and Squamous Cell Tumors in Adult Heterozygotes

Loss of one copy of the human ATP2C1 gene, encoding SPCA1 (secretory pathway Ca(2+)-ATPase isoform 1), causes Hailey-Hailey disease, a skin disorder. We performed targeted mutagenesis of the Atp2c1 gene in mice to analyze the functions of this Golgi membrane Ca(2+) pump. Breeding of heterozygous mutants yielded a normal Mendelian ratio among embryos on gestation day 9.5; however, null mutant (Spca1(-/-)) embryos exhibited growth retardation and did not survive beyond gestation day 10.5. Spca1(-/-) embryos had an open rostral neural tube, but hematopoiesis and cardiovascular development were ostensibly normal. Golgi membranes of Spca1(-/-) embryos were dilated, had fewer stacked leaflets, and were expanded in amount, consistent with increased Golgi biogenesis. The number of Golgi-associated vesicles was also increased, and rough endoplasmic reticulum had fewer ribosomes. Coated pits, junctional complexes, desmosomes, and basement membranes appeared normal in mutant embryos, indicating that processing and trafficking of proteins in the secretory pathway was not massively impaired. However, apoptosis was increased, possibly the result of secretory pathway stress, and a large increase in cytoplasmic lipid was observed in mutant embryos, consistent with impaired handling of lipid by the Golgi. Adult heterozygous mice appeared normal and exhibited no evidence of Hailey-Hailey disease; however, aged heterozygotes had an increased incidence of squamous cell tumors of keratinized epithelial cells of the skin and esophagus. These data show that loss of the Golgi Ca(2+) pump causes Golgi stress, expansion of the Golgi, increased apoptosis, and embryonic lethality and demonstrates that SPCA1 haploinsufficiency causes a genetic predisposition to cancer.

A Population-Based Study on the Association Between Parental Occupations and Some Common Birth Defects in Singapore (1994???1998)

We sought to study the association between some common birth defects and parental occupations. The live births and congenital malformation born between January 1994 and December 1998 were obtained from the Singapore National Registry of Births and Deaths (the National Birth Defect Registry). The prevalence of overall birth defects among Singapore live births during the study period is 13.9 per 1,000 live births. The most frequent single coding defects were "bulbus cordis anomalies and anomalies of cardiac septal closure (BCA)," "congenital anomalies of urinary system (CUS)," "cleft palate and cleft lip (CPL)," and "certain congenital musculoskeletal deformities (CMD)." Using the "Legislators, Senior Officers & Managers" as reference and adjusting for possible confounders, there were significant associations for: (1) paternal "clerical workers" (adjusted RR 2.25) with the BCA; (2) maternal "professionals" with CUS (adjusted risk ratio [RR] 3.58); (3) paternal "production craftsmen and related workers" with both the BCA (adjusted RR 2.04), and the CMD (adjusted RR 2.83); (4) paternal "plant and machine operators and assemblers" with the BCA (adjusted RR 2.49), and the CUS (adjusted RR 5.19), and the CMD (adjusted RR 3.01). Paternal rather than maternal exposure might be more important in the causation of some common birth defects in Singapore.

The structure and function of the helical heart and its buttress wrapping. II. Interface between unfolded myocardial band and evolution of primitive heart.

The unfolded myocardial band containing a central fold, extending between the pulmonary artery and aorta, has been used to explain the intact or wrapped cardiac structure, composed of a basal and apical loop forming a buttress and helix, connected to the outflow vessels of both ventricles. The interface between this simple structure, and embryologic development of the primitive heart evolving from a singular tube, into a dual pumping chamber with separate left and right sides, must be explained. The objective is to suggest that a simple and integrated triple figure-eight spiral band, with three S-shaped helixes and their apices may correlate the conventional embryologic development of the primitive heart (bulbus cordis, ventricle, and arterial outflow vessels), with the three stages of spatial orientation of the myocardial band (basal and apical loops), which extends between dual ventricular outflow vessels, in the sequence defined by the unwrapped myocardial band.

The rostro-caudal position of cardiac myocytes affect their fate.

During chick embryogenesis, cells destined to form cardiac myocytes are located within the primitive streak at stage 3 in the same relative anterior-posterior distribution as in the prelooped heart. The most rostral cells contribute to the extreme anterior pole of the heart, the bulbus cordis, and the most caudal to the extreme posterior end, the sinoatrial region. After gastrulation, these cells commit to the myocyte lineage and, retaining their relative positions, migrate to the anterior lateral plate. From stages 5 to 10 they diversify into atrial and ventricular myocytes, with the former located posteriorly and the latter, anteriorly. To determine the effect of a change in the rostro-caudal position of these cells on their diversification, anterior lateral plate mesoderm and the underlying endoderm were cut and rotated 180 degrees along the longitudinal axis, at stages 4-8. The subsequent diversification of these precursor cells into atrial and ventricular myocytes was examined using lineage-specific markers. Our results showed that altering location along the longitudinal axis through stage 6 changed the normal fate of a precursor cell. The orientation of the overlying ectoderm did not alter normal morphogenesis or determination of fate.

The application of adenoviral vectors in the study of mammalian cardiovascular development.

The application of adenoviral vectors in the study of mammalian cardiovascular development.

Jumonji gene is essential for the neurulation and cardiac development of mouse embryos with a C3H/He background

The recessive mutant mouse jumonji ( jmj), obtained by a gene trap strategy, shows neural tube defects in approximately half of homozygous embryos with a BALB/cA and 129/Ola mixed background, but no neural tube defects with BALB/cA, C57BL/6J, and DBA/2J backgrounds. Here, we show that neural tube and cardiac defects are observed in all embryos with a C3H/HeJ background. In addition, abnormal groove formation and prominent flexure are observed on the neural plate with full penetrance, suggesting that abnormal groove formation leads to neural tube defects. We found morphogenetic abnormalities in the bulbus cordis (future outflow tract and the right ventricle) of homozygous embryo hearts. Moreover, myocytes in the ventricular trabeculae show hyperplasia with cells filling the ventricles. Together with the observation that the jmj gene is expressed in the neural epithelium of the head neural plate and in myocytes in the bulbus cordis and trabeculae, the results show that the jmj gene plays essential roles in the normal development of the neural plate, morphogenesis of bulbus cordis, and proliferation of trabecular myocytes on a C3H/He background.

Inhibitory cholinergic effects on the autonomously contractile bulbus cordis branchialis of the cephalopod Sepia officinalis L.

In vitro experiments were performed on a standardized preparation of the autonomously contractile bulbus cordis branchialis of the branchial heart of Sepia officinalis to investigate its cholinergic neuroregulation. Apart from acetylcholine, nicotine and carbachol (nicotinic agonists), the muscarinic agonists muscarine, arecoline, pilocarpine, and oxotremorine also exerted concentration-dependent negative inotropic effects on the preparations. As both the muscarinic antagonist quinuclidinylbenzilate and the nicotinic antagonist α-bungarotoxin blocked the ACh action there might be a special, possibly mixed muscarinic/nicotinic ACh-receptor system in the myocytes of the bulbus cordis branchialis, which is different from the cholinergic receptor in the central part of the branchial heart.

Tbx5 is essential for heart development.

Mutations in the Tbx5 transcription factor cause heart septal defects found in human Holt-Oram Syndrome. The complete extent to which Tbx5 functions in heart development, however, has not been established. Here we show that, in Xenopus embryos, Tbx5 is expressed in the early heart field, posterior to the cardiac homeobox transcription factor, Nkx2.5. During morphogenesis, Tbx5 is expressed throughout the heart tube except the anterior portion, the bulbus cordis. When Tbx5 activity is antagonized with a hormone-inducible, dominant negative version of the protein, the heart fails to develop. These results suggest that, in addition to its function in heart septation, Tbx5 has a more global role in cardiac specification and heart development in vertebrate embryos.

Heart specific expression of mouse BMP-10 a novel member of the TGF-β superfamily

Here we report the cloning and expression of murine BMP-10, a novel member of the TGF-β superfamily. In the mouse embryo, BMP-10 expression begins at 9.0 d.p.c. and is restricted to the developing heart. Initially, BMP-10 expression localizes to the trabeculated part of the common ventricular chamber and to the bulbus cordis region. After 12.5 d.p.c., additional BMP-10 expression is seen in the atrial wall. The data presented here suggest that BMP-10 plays an important role in trabeculation of the embryonic heart.

Strain-dependent embryonic lethality in mice lacking the retinoblastoma-related p130 gene.

The retinoblastoma-related p130 protein is a member of a conserved family, consisting of Rb, p107 and p130, which are believed to play important roles in cell-cycle control and cellular differentiation. We have generated a null mutation in p130 by gene targeting and crossed the null allele into Balb/cJ and C57BL/6J strains of mice. In an enriched Balb/cJ genetic background, p130(-/-) embryos displayed arrested growth and died between embryonic days 11 and 13. Histological analysis revealed varying degrees of disorganization in neural and dermamyotomal structures. Immunohistochemistry with antibody reactive with Islet-1 indicated markedly reduced numbers of neurons in the spinal cord and dorsal root ganglia. Immunohistochemistry with antibody reactive with desmin indicated a similar reduction in the number of differentiated myocytes in the myotome. The myocardium of mutant embryos was abnormally thin and resembled an earlier staged two-chambered heart consisting of the bulbus cordis and the ventricular chamber. TUNEL analysis indicated the presence of extensive apoptosis in various tissues including the neural tube, the brain, the dermomyotome, but not the heart. Immunohistochemistry with antibody reactive with PCNA revealed increased cellular proliferation in the neural tube and the brain, and decreased proliferation in the heart. The placentas of p130(-/-) embryos did not display elevated apoptosis and were indistinguishable from wild type suggesting that the phenotype was not due to placental failure. Following a single cross with the C57BL/6 mice, p130(-/-) animals were derived that were viable and fertile. These results indicate that p130 in a Balb/cJ genetic background plays an essential role that is required for normal development. Moreover, our experiments establish that second-site modifier genes exist that have an epistatic relationship with p130.