Gene expression of insulin-like growth factor-I receptor and p53 suppressor during zebrafish (Danio rerio) embryogenesis.

In vertebrates insulin-like growth factors (IGFs) regulate important cellular activities involving proliferation, differentiation, and antiapoptosis and their biological activities are mediated through the insulin-like growth factor-I receptor (IGF-IR). To understand the functions of IGF-IR in zebrafish embryogenesis, the polymerase chain reaction (PCR) cloning technique was applied to isolate the IGF-IR gene. A 5'-truncated 3285-nucleotide zebrafish IGF-IR sequence was assembled from 3 overlapping clones. This contained a partial coding region of 1550 nucleotides and a 1735-nucleotide 3' untranslated region. The deduced 515 amino acid residues included the conserved kinase domain and shared 60.9%, 61.1%, and 59.9% homology to human, mouse, and frog, respectively. To understand the relationship of IGF-IR with p53 suppressor gene during embryogenesis, expression of both genes was analyzed in parallel by semicompetitive reverse transcriptase PCR and whole-mount in situ hybridization. This analysis indicated that messenger RNA of both genes was of maternal origin, but the p53 suppressor mRNA was relatively more abundant than the IGF-IR message in most of the developmental stages, except possibly at 28 hours postfertilization. At this stage the IGF-I receptor message was highly expressed and visible in whole internal organ regions by whole-mount in situ hybridization, while p53 message was concentrated in the head portion and barely detectable in the trunk portion. The results suggest that IGF-IR and p53 mRNA are expressed at different places and different times. However, the temporal and spatial relationship of IGF-IR and its relationship to p53 suppressor protein during developmental processes remain unknown.