The Nf1 knockout (8 (link)), Nf1 flox (9 (link)), Hoxb7-Cre (47 (link)), Lats1 flox (48 (link)), Lats2 flox (48 (link)) ROSA26-YFP (49 (link)), ROSA26-lacZ and athymic nude mice (Foxn1−/−) are available from Jackson Laboratory (Bar Harbor, ME). Genotyping was performed by PCR as previously reported (8 (link), 9 (link), 47 (link)–49 (link)). All mice were housed in the Animal Care Facility at The University of Texas Southwestern Medical Center (Dallas, TX), and all procedures were approved by Institutional Animal Care and Use Committee at University of Texas Southwestern Medical Center and conformed to NIH guidelines. Human subjects and cNF sample collection and use were approved by Institutional Review Board at University of Texas Southwestern Medical Center and conformed to NIH guidelines. Written informed consent was obtained from patients.