THE ZEBRAFISH FGF-3 GENE - CDNA SEQUENCE, TRANSCRIPT STRUCTURE AND GENOMIC ORGANIZATION

We report the isolation and characterization of genomic and cDNA clone s encoding zebrafish fibroblast growth factor 3 (FGF3). An initial cDN A clone was generated by PCR amplification using degenerate oligo prim ers corresponding to a conserved region of protein found in the mouse and human homologues. Screening a cDNA library made from 30-33-h-old z ebrafish embryos with this PCR product led to the isolation of two cDN A clones. Sequence analysis of the longest cDNA insert (1810 bp) revea led a 256-amino-acid (aa) orf. The central region, composed of approx. 155 aa, shares 78% identity with the analogous region of Xenopus laev is FGF3 and 72% identity with the product of the more distantly relate d human gene. However, the N- and C-terminal domains of zebrafish FGF3 are very different from those of other known homologues. The cDNA was used as a probe on genomic DNA to create a physical map of the locus and to isolate a genomic clone encompassing the entire coding region a nd 5' sequences. DNA sequencing and RNase protection analyses indicate that zebrafish Fgf-3 (ZFgf-3) is structurally analogous to the mouse gene sind regulated through two different promoters. The transcription start point of the proximal promoter aligns to that of mouse promoter P3 and lies within a conserved region of sequence.