Nonsyndromic total anomalous venous return associated with a de novo translocation inolving chromosomes 10 and 21 t(10;21)(q23.1;q11.2)

Myocardial overexpression of ANKRD1 causes sinus venosus defects and progressive diastolic dysfunction

AIMS

Increased Ankyrin Repeat Domain 1 (ANKRD1) levels linked to gain of function mutations have been associated to total anomalous pulmonary venous return and adult cardiomyopathy occurrence in humans. The link between increased ANKRD1 level and cardiac structural and functional disease is not understood. To get insight into this problem, we have generated a gain of function ANKRD1 mouse model by overexpressing ANKRD1 in the myocardium.

METHODS AND RESULTS

Ankrd1 is expressed non-homogeneously in the embryonic myocardium, with a dynamic nucleo-sarcomeric localization in developing cardiomyocytes. ANKRD1 transgenic mice present sinus venosus defect, which originates during development by impaired remodelling of early embryonic heart. Adult transgenic hearts develop diastolic dysfunction with preserved ejection fraction, which progressively evolves into heart failure, as shown histologically and haemodynamically. Transgenic cardiomyocyte structure, sarcomeric assembly, and stability are progressively impaired from embryonic to adult life. Postnatal transgenic myofibrils also present characteristic functional alterations: impaired compliance at neonatal stage and impaired lusitropism in adult hearts. Altogether, our combined analyses suggest that impaired embryonic remodelling and adult heart dysfunction in ANKRD1 transgenic mice present a common ground of initial cardiomyocyte defects, which are exacerbated postnatally. Molecular analysis showed transient activation of GATA4-Nkx2.5 transcription in early transgenic embryos and subsequent dynamic transcriptional modulation within titin gene.

CONCLUSIONS

ANKRD1 is a fine mediator of cardiomyocyte response to haemodynamic load in the developing and adult heart. Increased ANKRD1 levels are sufficient to initiate an altered cellular phenotype, which is progressively exacerbated into a pathological organ response by the high ventricular workload during postnatal life. Our study defines for the first time a unifying picture for ANKRD1 role in heart development and disease and provides the first mechanistic link between ANKRD1 overexpression and cardiac disease onset.

Maternal Obesity as a Risk Factor for the Development of Total Anomalous Pulmonary Venous Connection in Their Offspring

The incidence of total anomalous pulmonary venous connection (TAPVC) in the Caucasian population is 2.5/100,000 live births (LB), and the incidence in the Hispanic population is 19.8/100,000 LB. Without knowing the exact etiology for the development of congenital heart disease, our objective was to determine the maternal factors associated with the development of TAPVC.

METHODS

55 mother-child binomials with isolated TAPVC (group I) and 152 healthy mother-child binomials (group II) were included. Both groups had no maternal history of addiction, pre-eclampsia, or type 1, 2 or gestational diabetes mellitus. Complete clinical histories were obtained for the women in both groups and perinatal and birth data were recorded. In addition, genealogies across three generations were constructed to determine affected first- or second-degree relatives with complex congenital heart disease.

RESULTS

Among the maternal characteristics analyzed, women in group I had a higher number of pregnancies before gestation of the index case (p = <0.05), and the Body Mass Index (BMI) before pregnancy was higher compared to Group II (p < 0.05), with an adjusted risk of OR = 3.6 (p = 0.011). The family history showed a higher prevalence in the group of patients with TAPVC compared to healthy children (p < 0.05).

CONCLUSION

Maternal obesity before pregnancy is a risk factor for the development of CATVP in children in the Mexican population.

Transcriptional deregulation and a missense mutation define ANKRD1 as a candidate gene for total anomalous pulmonary venous return

Total anomalous pulmonary venous return (TAPVR) is a congenital heart defect in which the pulmonary veins fail to enter the left atrium and drain instead into the right atrium or one of its venous tributaries. Although a genetic basis for TAPVR has long been recognized, no single gene involved in the pathogenesis of this disease has been identified to date. We previously reported a TAPVR patient bearing a de novo 10;21 balanced translocation. In this work, we cloned both translocation breakpoints from this patient and mapped the ANKRD1 gene, encoding a cardiac transcriptional regulator, 130 kb proximally to the breakpoint on chromosome 10. In situ hybridization analysis performed on murine embryos showed ANKRD1 expression in the developing pulmonary veins, suggesting a possible role for this gene in TAPVR pathogenesis. Moreover, ANKRD1 expression levels were found to be highly increased in lymphoblastoid cell lines derived from both the translocation-bearing proband and a second independent sporadic TAPVR patient, suggesting that disruption of the normal ANKRD1 expression pattern is associated with TAPVR. Finally, a nonconservative missense mutation in the ANKRD1 gene was found in a third sporadic TAPVR patient. In vitro calpain-mediated degradation assays, coupled to reporter gene analysis in transfected HeLa cells, strongly suggested that this mutation enhances both the stability of the ANKRD1/CARP protein and its transcriptional repression activity upon the cardiac-specific atrial natriuretic factor (ANF) promoter. Taken together, these results define ANKRD1 as a possible candidate gene for TAPVR pathogenesis.

Mosaic ring 12p and total anomalous pulmonary venous return

An infant born with total anomalous pulmonary venous return (TAPVR) was found to have an extra chromosome present as a small ring. Spectral karyotyping and FISH analysis identified the material as a duplication involving the short arm of chromosome 12. Previous cases describing a variety of cytogenetic abnormalities that have been associated with TAPVR are reviewed along with prior cases of duplication 12p with their associated findings. We believe ours is the first case to report the occurrence of mosaic ring 12p and its association with TAPVR.