MGI:97307Homozygous targeted null mutants lack extraembryonic ectoderm, do not initiate gastrulation and die by embryonic day 7. Heterozygotes develop malignant tumors, especially osteosarcomas. Conditional Schwann cell knockouts resemble neurofibromatosis type 2. Mice homozygous for a conditional allele activated in the eye exhibit coloboma.