EXPRESSION OF THE AXOLOTL HOMOLOG OF MOUSE CHAPERONIN T-COMPLEX PROTEIN-1 DURING EARLY DEVELOPMENT

Molecular chaperones assist in the folding of proteins, but their role during development is not well understood. Here we report the tempora l and spatial expression pattern of the axolotl homologue of mouse cha peronin TCP-1 during normal amphibian embryogenesis and in several mod els of abnormal embryogenesis. A partial axolotl TCP-1 cDNA (646 bp; 5 19 coding bp) isolated by 3' RACE PCR shows considerable homology to m ouse TCP-1. Developmental Northerns and RT-PCR analyses of whole axolo tl embryos revealed a low level of maternal TCP-1 transcripts in ferti lized eggs. The maternal transcripts were down-regulated to a non-dete ctable level in early gastrulae. Zygotic TCP-1 transcripts first appea red during gastrulation. They were mainly expressed in mid-neurula and later stage embryos. Whole-mount in situ hybridization studies showed abundant TCP-1 transcripts in the blastopore at the mid-gastrula stag e and in the brain and spinal cord beginning at the neurula stage, and in the somites (myotomes) at the tailbud stage. RT-PCR analysis of TC P-1 expression in axolotl embryos treated with either high salt (causi ng exogastrulation) or ultraviolet (UV) irradiation (causing ventraliz ation) substantiated the correlation between TCP-1 expression and neur al and semitic development. In high salt-induced exogastrulated embryo s TCP-1 mRNA was detectable in the ectoderm part (with neural tissues) but not in its exogastrulated endoderm part. Lower levels of TCP-1 ex pression were detected in UV-irradiated, ventralized embryos with smal ler head and reduced neural and semitic tissues. Normal levels of TCP- 1 expression were detected in embryos with double axes/heads. These st udies provide strong evidence that at the transcript level axolotl cha peronin TCP-1 is regulated both temporally and spatially during embryo genesis, especially in neural and semitic development.