Insertion of GCGG between bases 4:273692 and 4:273693 , base 4:273689 changed from A to G, and base 4:273690 changed from A to T resulting in the addition of RAEVGFPSSWKTQKRHYTRKSRGFCAIYNREKKINLCSLKPRSKGKNETN after lysine 86 of all NfI isoforms and premature truncation after these novel amino acids.