ANALYSIS OF THE SEQUENCE AND EMBRYONIC EXPRESSION OF CHICKEN NEUROFIBROMIN MESSENGER-RNA

Neurofibromatosis type 1 (NF1) is a common inherited disorder that pri marily affects tissues derived from the neural crest. Recent identific ation and characterization of the human NF1 gene has revealed that it encodes a protein (now called neurofibromin) that is similar in sequen ce to the ras-GTPase activator protein (or ras-GAP), suggesting that n eurofibromin may be a component of cellular signal transduction pathwa ys regulating cellular proliferation and/or differentiation. To initia te investigations on the role of the NF1 gene product in embryonic dev elopment, we have isolated a partial cDNA for chicken neurofibromin. S equence analysis reveals that the predicted amino acid sequence is hig hly conserved between chick and human. The chicken cDNA hybridizes to a 12.5-kb transcript on RNA blots, a mol wt similar to that reported f or the human and murine mRNAs. Ribonuclease protection assays indicate that NF1 mRNA is expressed in a variety of tissues in the chick embry o; this is confirmed by in situ hybridization analysis. NF1 mRNA expre ssion is detectable as early as embryonic stage 18 in the neural plate . This pattern of expression may suggest a role for neurofibromin duri ng normal development, including that of the nervous system.