Cloning of leptin cDNA and assignment to the long arm of chromosome 5 in the marsupial Sminthopsis crassicaudata

We have isolated and sequenced full-length cDNA clones for leptin in the da syurid marsupial Sminthopsis crassicaudata (fat-tailed dunnart). Southern a nd in situ hybridisation data indicated a single leptin gene in the S. cras sicaudata genome, localised to arbitrary chromosome bands 5q24--> q31 on th e long arm of chromosome 5, the short-arm terminus of which bears the only nucleolar organising region. The nucleotide sequence of the cDNAs revealed that the primary translation product of S. crassicaudata leptin is composed of 167 amino acid residues, with a potential signal peptide of 21 residues . The mature protein of 146 amino acids is 82% similar to both the mouse an d human proteins and is predicted to have a molecular weight of 16.26 kDa. Northern blot analysis revealed that the corresponding mRNA is approximatel y 3.9 kb in size and is expressed only in white adipose tissue of this mars upial species. Evolutionary analyses indicate that S. crassicaudata leptin cDNA has evolved at a significantly faster rate than cDNAs from eutherian m ammals. Copyright (C) 2000 S. Karger AG, Basel.