Getting the T-box dose right.

Reports on the results of a study of a mouse model of Holt-Oram syndrome, which has been associated with mutations in the T-box transcription factor TBX5. Its function; How mutations in it can cause disease; Results of previous studies; Effects of experimental changes in TBX5 expression on heart and limb development in various species; Influence of genetic background on disease manifestations; Importance of considering species-specific gene expression patterns; Conclusions.