In humans, these heterozygous conditions can lead to syndromes, including Holt-Oram Syndrome (HOS, TBX5), ulna mammary syndrome (UMS, TBX3), DiGeorge syndrome (TBX1), spondylocostal dysostosis (TBX6) and cleft palate and ankyloglossia (TBX22) (reviewed in Ghosh et al., 2017). Here, TBX3 is linked to Holt-Oram syndrome.