Abstract

Congenital Heart Disease (CHD) is the most common birth defect, affecting approximately 1% of live births. This dissertation explores the genetic mechanisms underlying CHD, focusing on the T-box transcription factors Tbx2a and Tbx2b in zebrafish. Utilizing advanced bioinformatics techniques, we reconstructed the ancestral sequences of these genes to understand their evolutionary trajectory and functional divergence. Our analysis highlights the evolutionary conservation of the DNA-binding domain in tbx2a and tbx2b, suggesting its crucial role in maintaining correct gene expression patterns during development. We observed unique and shared amino acid substitutions in these proteins, indicating potential adaptive changes and conserved functions. Comparative sequence analysis with human Tbx2 revealed a high degree of conservation, underscoring the importance of these transcription factors across species. Functional studies in zebrafish demonstrated that both homozygous and heterozygous mutations in tbx2a and tbx2b result in heart looping defects, challenging the assumption of their redundancy. This indicates that these genes have unique, non-overlapping functions essential for cardiac development. The observed phenotypic variability in heterozygous mutants suggests a complex interplay between these genes, highlighting the sensitivity of cardiac development to precise gene dosage. Given their highly conserved DNA-binding domains, we proposed that Tbx2a and Tbx2b interact with different nuclear factors to regulate distinct sets of genes. In examining the differential roles of Tbx2a and Tbx2b, we were able to identify distinct patterns of protein binding that support our hypothesis of their functional divergence. This was achieved through mass spectrometry-based proteomics, which provided insights into the unique nuclear interactions of Tbx2a and Tbx2b. Overall, this research provides new insights into the functional and evolutionary roles of Tbx2a and Tbx2b in heart development, with implications for understanding the genetic basis of CHD.

Degree

PhD

College and Department

Life Sciences; Physiology and Developmental Biology

Rights

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