Expression of fibroblast growth factors 4, 8, and 10 in limbs, flanks, and blastemas of Ambystoma.
Members of the fibroblast growth factor (FGF) family of molecules are critical to limb outgrowth. Here, we examine the expression of Fgfs in three types of limbs-embryonic (developing), mature (differentiated), and regenerating-as well as in the surrounding non-limb tissues in the Mexican axolotl, Ambystoma mexicanum. We have previously cloned partial cDNAs of Fgf4, 8, and 10 from the axolotl (Christensen et al., 2001); the complete Fgf10 cDNA sequence is presented here. Axolotl Fgf10 showed deduced amino acid sequence identity with all other vertebrate Fgf10 coding sequences of >62%, and also included conserved 5' and 3' untranslated regions in nucleotide sequence comparisons. Semiquantitative reverse transcriptase-polymerase chain reaction showed that fibroblast growth factors are differentially expressed in axolotl limbs. Only Fgf8 and 10 were highly expressed during axolotl limb development, although Fgf4, 8, and 10 are all highly expressed during limb development of other vertebrates. Fgf4 expression, however, was highly expressed in the differentiated salamander limb, whereas expression levels of Fgf8 and 10 decreased. Expression levels of Fgf8 and 10 then increased during limb regeneration, whereas Fgf4 expression was completely absent. In addition, axolotl limb regeneration contrasted to limb development of other vertebrates in that Fgf8 did not seem to be as highly expressed in the distal epithelium; rather, its highest expression was found in the blastema mesenchyme. Finally, we investigated the expression of these Fgfs in non-limb tissues. The Fgfs were clearly expressed in developing flank tissue and then severely downregulated in mature flank tissue. Differential Fgf expression levels in the limb and shoulder (limb field) versus in the flank (non-limb field) suggest that FGFs may be instrumental during limb field specification as well as instrumental in maintaining the salamander limb in a state of preparation for regeneration.
Christensen
Randolph N
RN
Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA. christensen.40@osu.edu
Weinstein
Michael
M
Tassava
Roy A
RA
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000557:Ambystoma / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004848:Epithelium / Q000378:metabolism; D005121:Extremities / Q000293:injuries / Q000502:physiology*; D051526:Fibroblast Growth Factor 10; D051519:Fibroblast Growth Factor 4; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000096:biosynthesis* / Q000235:genetics; D005353:Fibronectins / Q000096:biosynthesis / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005796:Genes; D006801:Humans; D017403:In Situ Hybridization; D008648:Mesoderm / Q000378:metabolism; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D012038:Regeneration / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D013045:Species Specificity; D014714:Vertebrates / Q000235:genetics; D014945:Wound Healing / Q000502:physiology
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D018076:DNA, Complementary; C496463:FGF10 protein, human; C496445:FGF4 protein, human; D051526:Fibroblast Growth Factor 10; D051519:Fibroblast Growth Factor 4; D005353:Fibronectins; D011518:Proto-Oncogene Proteins; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors