Analysis of the sequence and embryonic expression of chicken neurofibromin mRNA

Neurofibromatosis type 1 (NF1) is a common inherited disorder that primarily affects tissues derived from the neural crest. Recent identification and characterization of the human NF1 gene has revealed that it encodes a protein (now called neurofibromin) that is similar in sequence to the ras-GTPase activator protein (or ras-GAP), suggesting that neurofibromin may be a component of cellular signal transduction pathways regulating cellular proliferation and/or differentiation. To initiate investigations on the role of the NF1 gene product in embryonic development, we have isolated a partial cDNA for chicken neurofibromin. Sequence analysis reveals that the predicted amino acid sequence is highly 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 for the human and murine mRNAs. Ribonuclease protection assays indicate that NF1 mRNA is expressed in a variety of tissues in the chick embryo; this is confirmed by in situ hybridization analysis. NF1 mRNA expression is detectable as early as embryonic stage 18 in the neural plate. This pattern of expression may suggest a role for neurofibromin during normal development, including that of the nervous system.