Whole-exome sequencing of pathogenic genes in a family with congenital heart disease: A case report

RATIONALE

Congenital heart disease (CHD) is the most common birth defect and an important cause of noninfectious deaths in infants and children. It has high prevalence globally, placing an enormous burden on society and families. Studies of individuals with hereditary or sporadic CHD have provided strong evidence for its genetic basis. The aim of this study was to identify causative gene variants in a Chinese family with congenital heart disease.

PATIENT CONCERNS AND DIAGNOSES

Three generations of a CHD family were recruited. Proband III.9 was diagnosed with congenital heart disease at age 11 months, and the echocardiogram showed arterial ductus arteriosus, with a left-to-right shunt at the level of the arteries. Precedent III.10 was a twin of Proband III.9 who was diagnosed with congenital heart disease at age 11 months, in whom the echocardiogram revealed an arterial ductus arteriosus, an unenclosed patent ductus arteriosus, and a left to right shunt at the level of the arteries (second figure). III.8 was diagnosed with congenital heart disease at age 15, but echocardiography in this study showed no abnormalities. No cardiac abnormalities were detected in any of his parents, grandparents, or maternal grandparents. We performed whole-exome sequencing on CHD sufferers and their unexpressing family members to investigate the genetic causes of CHD in this family line. Exome sequencing identified 4 mutation sites in this family line. The variant c.3245A>G (p.His1082Arg) of the AMER1 gene was consistent with concomitant X-chromosome recessive inheritance, the variant c.238G>C (p.Val80Leu) of the KCNE1 gene was consistent with autosomal accessory inheritance, and the other 2 variants did not conform to the law of the mode of inheritance of the disease.

OUTCOMES

The first identified variant, c.3245A>G (p.His1082Arg) of the AMER1 gene, with X-chromosome recessive inheritance, and the variant c.238G>C (p.Val80Leu) of the KCNE1 gene, which has been reported as autosomal dominant, may be the causative agent of CHD in this family line. These findings broaden the genetic scope of congenital heart disease and could help in the development of targeted drugs for the treatment of congenital heart disease.

Left atrial function during pregnancy: a three-dimensional echocardiographic study

BACKGROUND

Alteration of diastolic function is considered a sensitive means for detecting changes in the normal cardiac adaptation to pregnancy. Our aim was to evaluate volumetric and functional atrial parameters, using real time three-dimensional echocardiography (RT3DE) in women in early and late third trimester of pregnancy.

METHODS

We studied pregnant women in early third trimester (III-E = gestational age 26-33 weeks), in late third trimester (III-L = gestational age 34-40 weeks), and control nonpregnant women (C). Two-dimensional (2D-Echo) and RT3DE were used to study 3D left atrial (LA) systolic and diastolic stroke volumes and index (LASVI, LAEDVI), emptying fraction, left ventricular and LA cavities.

RESULTS

Although the LA end systolic volume index increased significantly (from 19.42 ± 0.1 to 24.7 ± 3.5 mm(2), P < 0.01), the EF did not change significantly. This was mainly achieved by increasing atrial contraction (A-wave), maintaining cardiac output by increasing heart rate. A decrease in diastolic E-wave, increased atrial kick (A-wave) with reduced E/A ratio, was noted as the pregnancy progressed. Pulmonary pressure increased from 16.9 ± 6.6 to 20.5 ± 2.9 mmHg (P < 0.01), Using 2D-Echo revealed no change in LA diameter from control to III-E and III-L, respectively (from 17.1 ± 2.3 to 16.7 ± 2.6, 17.5 ± 2.2 mm) and area (from 11.7 ± 3.1 to 16.5 ± 2.3, 17.6 ± 1.6 cm(2)). However, using RT3DE, a significant increase in the LASVI, LAEDVI, and LA stroke volume index (from 12.02 ± 2.5 to 14.7 ± 3.2, and 15.1 ± 2.7 mL/m(2)) was detected.

CONCLUSIONS

Enlargement of the LA volume with unchanged blood pressure values, as found using RT3DE, may be part of the adaptation to increased blood volume during pregnancy.

Islet1-expressing cardiac progenitor cells: a comparison across species

Adult mammalian cardiac stem cells express the LIM-homeodomain transcription factor Islet1 (Isl1). They are considered remnants of Isl1-positive embryonic cardiac progenitor cells. During amniote heart development, Isl1-positive progenitor cells give rise mainly to the outflow tract, the right ventricle, and parts of the atria. This led to the hypothesis that the development of the right ventricle of the amniote heart depends on the recruitment of additional cells to the primary heart tube. The region from which these additional, Isl1-positive cells originate is called second heart field, as opposed to the first heart field whose cells form the primary heart tube. Here, we review the available data about Isl1 in different species, demonstrating that Isl1 is an important component of the core transcription factor network driving early cardiogenesis in animals of the two clades, deuterostomes, and protostomes. The data support the view of a single cardiac progenitor cell population that includes Isl1-expressing cells and which differentiates into the various cardiac lineages during embryonic development in vertebrates but not in other phyla of the animal kingdom.

Improving cardiac regeneration after injury: are we a step closer?

During regeneration, lost functional tissue can, in general, be replaced by different mechanisms, including proliferation of terminally differentiated cells or through differentiation of resident stem cells. It is a well-accepted dogma that the mammalian heart cannot efficiently regenerate upon injury as a consequence of insufficient oxygen supply. This is in sharp contrast to the hearts of adult zebrafish or newts that are able to replace lost ventricular tissue. Novel data indicate that the young murine heart also has the ability to regenerate within the first week after birth using mechanisms apparently quite similar to those observed in fish. This now provides us with a good starting point to identify the molecular mechanisms that led to the loss of the regenerative capacity of the adult mammalian heart. These future studies will also indicate whether it will be possible to reawaken the regenerative capability of cardiomyocytes in the human heart by treatment with selected pharmaceuticals.

Signaling pathways in early cardiac development

Cardiomyocyte differentiation is a complex multistep process requiring the proper temporal and spatial integration of multiple signaling pathways. Previous embryological and genetic studies have identified a number of signaling pathways that are critical to mediate the initial formation of the mesoderm and its allocation to the cardiomyocyte lineage. It has become clear that some of these signaling networks work autonomously, in differentiating myocardial cells whereas others work non-autonomously, in neighboring tissues, to regulate cardiac differentiation indirectly. Here, we provide an overview of three signaling networks that mediate cardiomyocyte specification and review recent insights into their specific roles in heart development. In addition, we demonstrate how systems level, 'omic approaches' and other high-throughput techniques such as small molecules screens are beginning to impact our understanding of cardiomyocyte specification and, to identify novel signaling pathways involved in this process. In particular, it now seems clear that at least one chemokine receptor CXCR4 is an important marker for cardiomyocyte progenitors and may play a functional role in their differentiation. Finally, we discuss some gaps in our current understanding of early lineage selection that could be addressed by various types of omic analysis.