Abstract
We have investigated the occurrence of Insulin-like Growth Factor I (IGF-I) and IGF-II specific messenger RNAs in human fetal tissues (liver, kidney, lung, heart, adrenal, brain, muscle, jejunum, thymus, spleen, pancreas) and adult liver and kidney. In human fetal tissues and in the adult kidney IGF-I mRNA is barely detectable as a 7.6 kb band. In adult human liver a 7.6 kb mRNA species can be readily detected, along with species of around 1.1 kb and a broader zone of hybridization between 2.5 and 5 kb. In rat and mouse liver a similar pattern is observed. The pattern of hybridization with IGF-II cDNA contrasts sharply with these results: by far the highest abundance of IGF-II specific mRNA is found in fetal tissues, notably the liver (species of 6.0, 4.8, 4.1 and 2.1 kb). Tissue specificity is not very prominent. In human adult liver only a 5.3 kb IGF-II mRNA species can be detected, while the pattern in adult human kidney resembles that of fetal tissues. Combination of these data with the analysis of the human IGF-II gene has revealed that the different IGF-II mRNAs arise from the development and tissue-specific activation of at least three different promoters in the IGF-II gene. Considering the relative smallness of the preproIGF molecules encoded (less than 200 amino acid residues), the length of the mRNA transcripts is remarkable. The significance of this phenomenon, e.g. with respect to mRNA stability and translatability, requires further investigation.
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Jansen, M., de Pagter-Holthuizen, P., Sussenbach, J. et al. EXPRESSION OF THE INSULIN LIKE GROWTH FACTOR GENES IN HUMAN FETAL AND ADULT TISSUES. Pediatr Res 23, 108 (1988). https://doi.org/10.1203/00006450-198801000-00040
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DOI: https://doi.org/10.1203/00006450-198801000-00040