 It has been suggested that the quantitative differences in expression between the different isoforms may be related to the phenotypic variability of neurofibromatosis type 1 patients.In the "NF1" mRNA, there is a site within the first half of the GRD where mRNA editing occurs.Deamination occurs at this site, resulting in the conversion of cytidine into uridine at nucleotide 3916.