Taken together, our data provide structural insight into the interaction of Spred1 and neurofibromin and characterize the structural or functional consequence of selected patient-derived mutations associated with Legius syndrome.
These syndromes include Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML or LEOPARD syndrome), neurofibromatosis type 1 (NF1), Costello syndrome (CS), cardio-facio-cutaneous (CFC) syndrome, neurofibromatosis type 1-like syndrome (NFLS or Legius syndrome) and capillary malformation-arteriovenous malformation syndrome (CM-AVM).
These data clearly demonstrate that SPRED1 inhibits the Ras-ERK pathway by recruiting neurofibromin to Ras through the EVH1-GRD interaction, and this study also provides molecular basis for the pathogenic mutations of NF1 and Legius syndrome.
Neurofibromatosis type 1 (NF1) and Legius syndrome are related diseases with partially overlapping symptoms caused by alterations of the tumor suppressor genes NF1 (encoding the protein neurofibromin) and SPRED1 (encoding sprouty-related, EVH1 domain-containing protein 1, Spred1), respectively.
The discovery of SPRED1 as a cause of Legius syndrome which is manifested by CAL, freckling and learning difficulties has introduced substantial heterogeneity to the NIH criteria.
Legius syndrome is a recently described syndrome caused by Sprouty-related, Ena/vasodilator-stimulated phosphoprotein homology-1 domain containing protein 1 (SPRED1) mutations that also has multiple café-au-lait macules and intertriginous freckling.
Loss-of-function mutations in one feedback regulator of Ras/MAPK signaling, SPRED1 (Sprouty-related protein with an EVH1 domain), cause Legius syndrome, an autosomal dominant human disorder that resembles Neurofibromatosis-1 (NF1).
To determine if copy number changes (CNCs) are a cause of Legius syndrome, we have used a Multiplex Ligation-dependent Probe Amplification (MLPA) assay covering all SPRED1 exons in a cohort of 510 NF1-negative patients presenting with multiple CALMs with or without freckling, but no other NF1 diagnostic signs.
To determine if copy number changes (CNCs) are a cause of Legius syndrome, we have used a Multiplex Ligation-dependent Probe Amplification (MLPA) assay covering all SPRED1 exons in a cohort of 510 NF1-negative patients presenting with multiple CALMs with or without freckling, but no other NF1 diagnostic signs.
Patients fulfilling the National Institutes of Health (NIH) diagnostic criteria for NF1 were enrolled at the University of Utah NF Clinic, and SPRED1 mutation analysis was performed to identify the frequency of Legius syndrome within an NF1 clinic population.