Nucleotide sequence and expression of ribosomal protein S3 mRNA during embryogenesis in the Mexican axolotl (Ambystoma mexicanum).

We have isolated and sequenced a full-length (0.9 kb) cDNA clone of ribosomal protein S3 by subtraction hybridization using a single-stranded cDNA library from stage 25-27 (tracer) and the mRNA from stage 15-17 (driver) of embryonic Mexican axolotl (Ambystoma mexicanum). The axolotl is a unique animal model for studying heart development as well as myofibrillogenesis because it carries a mutation in gene c. The deduced amino acid sequence of axolotl S3 protein shows about 93.9% identity with human S3 protein over a 243 amino acid residue overlap. When compared with mouse and Xenopus laevis ribosomal S3 proteins, the axolotl sequenc shows 94.3 and 93.9% identity respectively. Interestingly, the axolotl S3 sequence shows higher identity at the nucleic acid level with human and/or other mammals than with Xenopus. The S3 transcript, as determined by RT-PCR, is present at stage 2-4 in a lower amount and the onset of transcription is most likely at the beginning of gastrulation (10-12). The expression level of S3 transcripts reaches a maximum by mid gastrulation (stages 13-14) and then follows a biphasic pattern being lower at stages 16-17 with subsequently steady increases until the mid tailbud stages (25-27).