Unidirectional blood flow, controlled by valves within the heart, is an essential component for proper and efficient heart function. 30% of patients exhibiting a congenital heart defect present with defects in these valves resulting in decreased heart function. In zebrafish, valve formation occurs at the atrioventricular canal (AVC) and outflow tract (OFT). The signaling pathways for valve formation are not completely understood. Here we present analysis of the novel pendulum mutant with a focus on its molecular nature. Phenotypic characteristics of the pendulum mutant include regurgitating blood flow in the heart, reduced heart rate, and reduced or absent blood circulation throughout the body at 3 days post fertilization (3 dpf). Preliminary analysis of pendulum mutants suggested that changes in gene expression result in defects in the development of the bulboventricular (BV) valve and nearby smooth muscle of the outflow tract. tbx5a is a gene that plays a critical role in the development of the heart and forelimbs in zebrafish. Lysine acetyltransferase KAT2b is responsible for the acetylation of the TBX5 protein in cell culture. Morpholino-mediated knockdown of kat2b in zebrafish has been shown to impact the expression of tbx5a, resulting in a phenotype comparable to that of pendulum mutants. To determine the possible relationship between the kat2b gene and pendulum mutants a characterization of the kat2b gene will be performed. This will include a detailed analysis regarding gene sequence in pendulum siblings and mutants, expression level and location using in situ hybridization, and the impact of kat2b mRNA over-expression in both pendulum mutants and their sibling counterparts. Understanding the molecular cause of this mutant will provide novel insight into valve and outflow tract development.
Author(s): Griffin Chadwick, Biology Major
Advisor(s): Jennifer Schumacher, Department of Biology