Noncompaction cardiomyopathy genetics

Overview
Noncompaction cardiomyopathy can appear sporadically or can be familial. Although mutations responsible for the sporadic cases have not been identified, several mutations that appear responsible for the familial transmission have been identified. 18% to 50% of family members are affected. There is predominantly an autosomal dominant mode of inheritance. There are more males with NCC than females which suggests a X linked pattern of inheritance in some patients. Noncompaction of ventricular myocardium was recently included in the 2006 classification of cardiomyopathies as a genetic cardiomyopathy.

Patterns of Inheritance
The majority of the time the pattern of inheritance is autosomal dominant. In some families, the mode of transmission appears to be x-linked or via mitochondrial transmission.

Genes Involved
Several potential genetic abnormalities have been identified:
 * The gene that encodes for alpha-dystrobrevin . This is a dystrophin-associated protein which has been mapped to chromosome 18q12. The role of this protein is to preserve the structural integrity of the muscle membrane.
 * An X-linked genetic defect which involves a mutation in the gene G4.5 (TAZ) of the Xq28 chromosome region (a gene which encodes for tafazzin), the same region of the chromosome involved in several myopathies with cardiac involvement are located. These include Barth syndrome, Emery-Dreifuss muscular dystrophy, and myotubular myopathy. As a result, some patients with NCC may have features of Barth syndrome.
 * Mutations of the ryanodine receptor 2 gene (RyR2) as has been seen in patients with arrhythmogenic right ventricular dysplasia.
 * Deletions of the FKBP12 gene result in noncompaction in the mouse.
 * Knockout of the Peg1 gene has been associated with NCC in the mouse.
 * LMNA mutations
 * Abnormalities of transcription factors such as NKX2.5 and TBX5.
 * Abnormalities of 11p15 as suggested in a GWAS analysis.
 * 22q11 deletion
 * Distal 5q deletion involving the CSX gene