The human neurofibromatosis 2 (NF2) gene has recently been isolated and predicted to encode a novel protein named merlin. Based on its high homology to the moesin-ezrin-radixin family of proteins, it may be involved in mediating interactions between the plasma membrane and the cytoskeleton. Here we report the isolation and characterization of multiple transcript isoforms of the mouse NF2 gene. The full length coding complementary DNA sequence of transcript isoform I is 1788 base pairs in length, shares 90% sequence identity with the human NF2 complementary DNA, and encodes a putative protein of 596 amino acids sharing 98% homology with the human merlin protein. Transcript isoforms II and III carry a 45- and 16-base pair insertion, respectively, at nucleotide 1740 at the 3' end, generated by two different modes of alternative splicing; both insertions introduce premature termination codons. Thus, transcript isoforms II and III predict proteins of 591 and 584 amino acids with altered COOH-termini of more hydrophilic character as compared to isoform I. Northern blot analysis and reverse transcription-polymerase chain reaction analysis indicate that the mouse NF2 gene is widely expressed in different tissue types and that the alternative transcripts are variantly expressed. The results presented here indicate high conservation of the NF2 gene during evolution and suggest a possible role for the COOH-terminus in mouse merlin function.