NF1 and skeletal dysplasia: The hyperthropic chondrocytes of the Nf1+/− embryos presented a high expression of phosphorylated p44/42 MAPK, suggesting that the activation of the Ras-MAPK pathway, resulting from NF1 protein haploinsufficiency, may be involved in the development of congenital skeletal dysplasias in NF1 patients.