Holt-Oram syndrome is a human condition that occurs in 1 in 100,000 births resulting in developmental defects in both heart and hand/arm. It is a result of haploinsufficiency due to a mutated copy of TBX5. Unlike humans, zebrafish have two copies of tbx5: tbx5a and tbx5b. Both Tbx5a and Tbx5b-deficient embryos display defects in heart and pectoral fin development. Although the role of Tbx5a in zebrafish fin development and the role of Tbx5 in heart and limb development in other animals has been well studied, much less is known about the roles Tbx5b plays during zebrafish development.
From expression data and morpholino data, it appears that Tbx5a and Tbx5b have overlapping but distinct roles in the development of the fin and heart. The role of Tbx5b in the lateral plate mesoderm was investigated and compared to the previously characterized functions of Tbx5a. RNA-sequencing identified targets of Tbx5a and Tbx5b and allowed for an unbiased comparison and approach towards identifying differences between Tbx5a and Tbx5b function at multiple time points during lateral plate mesoderm migration. These transcriptomics methods reveal similarities and differences between Tbx5a and Tbx5b function that may be reflected in their transcriptional networks.