TGFB1 and Marfan syndrome: Ski is a nuclear proto-oncogene protein homolog of the avian sarcoma viral (v-ski) oncogene and is a repressor of TGF-β and BMP signaling by inhibiting the transcription activity of SMAD complex.311 It also recruits histone deacetylases HDAC4 and HDAC5 as co-repressors.312SKI mutations in humans cause Shprintzen-Goldberg syndrome (GOSHS; MIM #182212),313 which share multiple skeletal anomalies with Marfan syndrome caused by mutations of FBN-1 (Table 2).