 "NF1" exon 1 is 544-bp long, contains the 5’ UTR and encodes the first 20 amino acids of neurofibromin.The "NF1" promoter lies within a CpG island that is 472-bp long, consisting of 43 CpG dinucleotides, and extends into the start of exon 1.This CpG Island begins 731-bp upstream of the promoter and no core promoter element, such as a TATA or CCATT box, has been found within it.