A novel DNAH11 variant segregating in a sibship with heterotaxy and implications for genetic counseling

Genetic Contributions to Biliary Atresia: A Developmental Cholangiopathy

Biliary atresia (BA) is the most prevalent serious liver disease of infancy and childhood, and the principal indication for liver transplantation in pediatrics. BA is best considered as an idiopathic panbiliary cholangiopathy characterized by obstruction of bile flow and consequent cholestasis presenting during fetal and perinatal periods. While several etiologies have been proposed, each has significant drawbacks that have limited understanding of disease progression and the development of effective treatments. Recently, modern genetic analyses have uncovered gene variants contributing to BA, thereby shifting the paradigm for explaining the BA phenotype from an acquired etiology (e.g., virus, toxin) to one that results from genetically altered cholangiocyte development and function. Herein we review recently reported genetic contributions to BA, highlighting the enhanced representation of variants in biological pathways involving ciliary function, cytoskeletal structure, and inflammation. Finally, we blend these findings as a new framework for understanding the resultant BA phenotype as a developmental cholangiopathy.

Pulmonary Hypertension in a Patient With Kartagener’s Syndrome and a Novel Homozygous Nonsense Mutation in CCDC40 Gene: A Case Report

Kartagener’s syndrome is a subgroup of primary ciliary dyskinesia (PCD), a genetically heterogeneous condition characterised by sinusitis, bronchiectasis, and situs in versus. Genetic testing has importance for their diagnosis. Here, we report a chinese patient with Kartagener’s syndrome. Transthoracic echocardiography showed severely elevated right ventricular systolic pressure. Right heart catheterisation demonstrated a pre-capillary pulmonary hypertension. Whole-exome sequencing indicated that she had a novel homozygous nonsense mutation, c.2845C > T, p.Gln949*, in exon 18 of CCDC40 and a heterozygotic mutation, c.73G > A, p.Ala25Thr, in exon 1 of DNAH11. She was diagnosed as Kartagener’s syndrome with pulmonary hypertension. Her symptoms improved significantly by treatment of antibiotics, expectorant drugs, bronchodilators, and oxygen therapy treatment. Our findings extend the mutation spectrum of CCDC40 gene related Kartagener’s syndrome, which is very important for gene diagnosis of the disease.

DNAH11 compound heterozygous variants cause heterotaxy and congenital heart disease

Heterotaxy (HTX), a condition characterized by internal organs not being arranged as expected relative to each other and to the left-right axis, is often accompanied with congenital heart disease (CHD). The purpose was to detect the pathogenic variants in a Chinese family with HTX and CHD. A non-consanguineous Han Chinese family with HTX and CHD, and 200 unrelated healthy subjects were enlisted. Exome sequencing and Sanger sequencing were applied to identify the genetic basis of the HTX family. Compound heterozygous variants, c.3426-1G>A and c.4306C>T (p.(Arg1436Trp)), in the dynein axonemal heavy chain 11 gene (DNAH11) were identified in the proband via exome sequencing and further confirmed by Sanger sequencing. Neither c.3426-1G>A nor c.4306C>T variant in the DNAH11 gene was detected in 200 healthy controls. The DNAH11 c.3426-1G>A variant was predicted as altering the acceptor splice site and most likely affecting splicing. The DNAH11 c.4306C>T variant was predicted to be damaging, which may reduce the phenotype severity. The compound heterozygous variants, c.3426-1G>A and c.4306C>T, in the DNAH11 gene might be the pathogenic alterations resulting in HTX and CHD in this family. These findings broaden the variant spectrum of the DNAH11 gene and increase knowledge used in genetic counseling for the HTX family.

A novel DNAH11 variant segregating in a sibship with heterotaxy and implications for genetic counseling

Background

Isomerism or heterotaxy syndrome is the loss of normal asymmetry of the internal thoraco‐abdominal organs in the left‐right axis and is associated with cardiovascular malformations. Mutations within DNAH11 can be associated with primary ciliary dyskinesia and heterotaxy syndromes.

Methods

We report a family of healthy, nonconsanguinous parents with subsequent pregnancies demonstrating a novel likely pathogenic variant in DNAH11 segregating in a sibship with varied presentations.

Result

The first affected pregnancy presented with right atrial isomerism. Further DNA testing identified three variants in DNAH11 related to primary ciliary dyskinesia: a maternally inherited heterozygous variant of unknown significance (VUS) c.2772G>A (p.Met924Ile), a maternally inherited novel likely pathogenic variant c.11662C>T (p.Arg3888Cys) as well as a paternally inherited pathogenic c.1648delA variant (p.Arg550GlyfsX16). The second pregnancy inherited the same variants including the pathogenic and likely pathogenic DNAH11 variants and presented with left isomerism and extracardiac abnormalities.

Conclusion

We present a novel likely pathogenic variant (c.11662C>T) in DNAH11 that has manifested in heterotaxy with variability in phenotypes for subsequent pregnancies of common parents. This report demonstrates that sibship illustrates potential variability in phenotypes associated with the same pathogenic variants within a family and highlights the difficulty in genetic counseling due to the variation in clinical presentation.