This model is also consistent with our observations in a mouse phenocopy of HOS, where we have shown that conditional deletion of Tbx5 in ICT fibroblasts, but not muscle or tendon cells, can cause abnormal muscle and tendon formation similar to that seen in HOS (Besse et al., 2020; Hasson et al., 2010). This evidence concerns the gene TBX5 and Holt-Oram syndrome.