This report describes atrial septal defect 4 (ASD4), which is a sub-type of atrial septal defect (ASD); ASD exhibits autosomal dominant inheritance. The human gene implicated in this disease is TBX20, which encodes a T-box transcription factor. There are 2 high-scoring fly orthologs, H15 and mid, for which classical amorphic and loss-of-function alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated. The two Drosophila orthologs map within 60kb of each other. They exhibit different expression patterns: H15 is more specifically expressed in cardiac tissues, especially in adults; mid is more broadly expressed, including in early embryos.
The human TBX20 gene has not been introduced into flies.
Most animals homozygous for amorphic mutations of Dmel\mid die during late embryogenesis; among other embryonic phenotypes, a partially penetrant heart phenotype is observed. Mutations of Dmel\H15 have not been well characterized. The penetrance of heart morphogenesis defects in embryos observed for RNAi-induced knockdown of mid is increased in an H15 mutant background.
[updated Apr. 2017 by FlyBase; FBrf0222196]