CDK13 function in heart development and congenital heart disease

ABSTRACT Mutations in the CDK13 gene cause “Congenital Heart Defects, dysmorphic Facial features, and Intellectual Developmental Disorder” (CHDFIDD); the link to this congenital heart disease (CHD) has spurred great interest about its molecular mechanism of action. We have developed genetic mouse and iPS cell models to investigate how mutations in this kinase lead to the associated cardiac pathologies. Several recent reports have provided additional evidence that also supports our hypothesis that reduced CDK13 function affects transcriptional and post-transcriptional RNA processing to disrupt cellular function. Consequences of inadequate CDK13 function may lead to defects in RNA splicing; in addition, depending on the level of CDK13 functional deficiency, compensatory mechanisms may be activated in the cell in an effort to remove aberrant RNAs. This could include the increased expression of spliceosome components, exosome factors, or RNAses. Therefore, we will test the hypothesis that CDK13 deficiency induces heart defects through disruption of RNA processing, generating functional deficiencies at the cellular level and impairing normal heart development. To accomplish this, we propose three integrative aims, including studies in both mouse and human iPSC models. For Aim 1, we will employ Cdk13 mutant mice with the genetic lesion specifically targeted to cardiomyocytes within the first heart field (FHF) or the second heart field (SHF). We will also delete Cdk13 from neural crest cells (NCC) as part of a systematic strategy to characterize the cardiac phenotype. We will also employ cellular and molecular biology approaches to determine the role of Cdk13 in cell proliferation, differentiation, and migration. In Aim 2, we will employ a cell based approach, using the innovative induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) model. This model will facilitate the testing of mutations in the CDK13 gene that are associated with CHDFIDD, based on published studies. Our approach will yield important new information on how each mutation contributes to the individual defects. Our preliminary studies have established proof of principle with the generation of iPSCs with CDK13 mutations corresponding to those found in CHDFIDD patients. Our characterization of the CDK13 mutant iPSC-CMs will establish a high throughput model of CHDFIDD that will facilitate both mechanistic studies and approaches to intervention and potential treatments. In Aim 3, we will focus on the molecular mechanisms of Cdk13 function. We and others have observed abnormal RNA processing associated with insufficient CDK13 function; our preliminary data highlights important potential links to RBFOX1 as well as several ribosomal proteins. We have designed a chemically inhibitable CDK13 line that will facilitate the study of a complete or partial loss of CDK13 function and facilitate a dissection of the molecular mechanism disrupted in CHDFIDD patients. Our proposed studies will provide important insights into CDK13 function and possible approaches for the treatment of CHDs and heart disease.