Expression of axolotl RNA-binding protein during development of the Mexican axolotl

Amphibians occupy a central position in phylogeny between aquatic and terre strial vertebrates and are widely used as model systems for studying verteb rate development. We have undertaken a comprehensive molecular approach to understand the early events related to embryonic development in the Mexican axolotl, Ambystoma mexicanum, which is an exquisite animal model for such explorations. Axolotl REP is a RNA-binding protein which was isolated from the embryonic Mexican axolotl by subtraction hybridization and was found to show highest similarity with human, mouse, and Xenopus cold-inducible RNA- binding protein (CIRP). The reverse transcriptase polymerase chain reaction (RT-PCR) analysis suggests that it is expressed in most of the axolotl tis sues except liver; the expression level appears to be highest in adult brai n. We have also determined the temporal and spatial pattern of its expressi on at various stages of development. RT-PCR and in situ hybridization analy ses indicate that expression of the AxRBP gene starts at stage 10-12 (gastr ula), reaches a maxima around stage 15-20 (early tailbud), and then gradual ly declines through stage 40 (hatching). In situ hybridization suggests tha t the expression is at a maximum in neural plate and neural fold at stage 1 5 (neurula) of embryonic development.