Genetically engineered minipigs model the major clinical features of human neurofibromatosis type 1

Abstract

Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in Neurofibromin 1 (NF1). NF1 patients present with a variety of clinical manifestations and are predisposed to cancer development. Many NF1 animal models have been developed, yet none display the spectrum of disease seen in patients and the translational impact of these models has been limited. We describe a minipig model that exhibits clinical hallmarks of NF1, including café au lait macules, neurofibromas, and optic pathway glioma. Spontaneous loss of heterozygosity is observed in this model, a phenomenon also described in NF1 patients. Oral administration of a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor suppresses Ras signaling. To our knowledge, this model provides an unprecedented opportunity to study the complex biology and natural history of NF1 and could prove indispensable for development of imaging methods, biomarkers, and evaluation of safety and efficacy of NF1-targeted therapies.

Longitudinal phenotype development in a minipig model of neurofibromatosis type 1

“…We found statistically smaller long bones (femur, tibia, humerus, ulna, metacarpals) in the NF1 +/ex42del minipigs compared to their wildtype siblings. Previous NF1 minipig studies found no difference in stature using external measurement of length and height 23 . However, prior studies have recorded strong association between femur measurement and human stature in adults 50 and children 51 and have been used as a surrogate measure of growth differences between rats 52 and pigs 53 .…”

“…Weight was not statistically significantly different between NF1 +/ex42del and wildtype minipigs at any of the three study time points (4, 8 and 12 months of age). Previous studies have indicated a reduced weight NF1 minipigs using a small selected cohort (N = 3) 23 .…”

“…Tibial bowing is a rare but distinctive phenotype in NF1 (3-4%) 37 , we report quantitative results of increased bilateral and unilateral bowing in NF1 minipigs out of the range of wildtype sibling controls, indicating a potential phenotype. Isakson et al described bilateral tibial dysplasia narrowing in two cloned boars using qualitative radiograph assessment but did not note other skeletal abnormalities in the F1 cohort 23 . Weight was not statistically significantly different between NF1 +/ex42del and wildtype minipigs at any of the three study time points (4, 8 and 12 months of age).…”

“…In this study we have excluded those potential effects by using naturally bred first generation (F1) minipigs. Isakson et al recently reported in an Ossabaw minipig model the development of CALMs (F0, F1), freckling (F1), Lisch nodules (F0), dermal neurofibroma (F0, F1), a glioma-like lesion in optic chiasm (F1), and tibial narrowing (F0) 23 . In this study's Yucatan F1 cohort we found no evidence of optic chiasm lesion.…”

“…Retrospectively collected imaging studies have assessed prevalence and NF1 findings in radiograph 8 , computed tomography (CT) 9 , magnetic resonance (MR) imaging 7,10,11 , and positron emission tomography (PET) 12 . As the NF1 population is more susceptible to the effects of radiation 13 , prospective studies are often limited to non-ionization radiation modalities such as MR 5,6,14,15 and ultrasound 16,17 .Efforts to create animal models of NF1 seek to provide the opportunity to explore treatment response and natural course [18][19][20][21][22][23][24] . Several murine models of NF1 have already been developed; however, mice are too small for the relevant medical imaging systems to be used in detection and monitoring the progression of NF1's phenotypes [19][20][21]24 .…”