NSD1 and Sotos syndrome: Sotos syndrome is caused by heterozygous inactivating variants in the nuclear receptor-binding SET domain protein gene (NSD1, OMIM #606681), which encodes a histone methyltransferase that preferentially methylates lysine 36 of histone H3 and lysine 20 of histone H4, either negatively or positively influencing transcription, depending on the cellular context [3,4].