TBX6 and Holt-Oram syndrome: 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).