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Molecular and functional analysis of DAND5 in human Congenital Heart Disease (CHD)

Publication . Cristo, Fernando Jorge Pego; Belo, José

The majority of congenital heart disease (CHD) is sporadic, with a minority of cases associated with a known genetic abnormality. Combinations of geneticenvironmental factors are implicated in the etiology of the disease. Recently, several studies, using mostly animal models, unraveled that perturbations in the molecular processes that precede the beginning of heart development might also be at the origin of CHD. In fact, some of the most complex CHDs are found associated with laterality defects, a disorder resulting from abnormal Left-Right axis formation. In our laboratory, the identified mouse Cerberus-like2 (Cerl2 – human DAND5), a protein that inhibit Nodal signaling, prompt us to study cardiac and laterality diseases, since the generated Cerl2 KO mice display a wide range of laterality defects and CHD. Considering the high conservation of genetic pathways regulating cardiac development in mouse and human, the main objective of the present thesis was the study of human genes involved in the Nodal pathway, focusing mostly in DAND5, in a CHD and/or laterality defects patients cohort. The sequence analysis of DAND5 revealed two patients displaying the same p.R152H variant, resulting in a substantial decreased in the function of the protein. We propose that p.R152H acts as a risk allele for CHD and/or laterality defects. In addition, we found two alterations in NODAL, two alterations in PITX2C and one alteration in CFC1. We hypothesized that the NODAL p.H165R variant can act as a common modifier and the intronic variants in NODAL and PITX2C might cause alterations in the splicing pattern of the mRNA molecules. Moreover, we generated patient-specific iPSCs to understand the molecular mechanisms of disease behind the DAND5 nucleotide variant. Although we cannot make a clearly genotype-phenotype correlation, the variants here identified probably increase the disease susceptibility due to the resulting abnormal Nodal signaling. Because most of the patients presented more than one alteration, the cumulative effect of each variant within the pathway seems to enhance even more these risk. Therefore, the imbalance in dosage-sensitive Nodal signaling is a common denominator for laterality defects and associated CHDs.

2017-05-19Doctoral thesis

Open Access