Journal of Korean Endocrine Society 1996;11(4):409-417.
Published online November 7, 2019.
Expression of Exon 1 and 6 of Indulin-like Growth Factor - 1 (IGF - 1) Gene in Thyroid Tissues.
Sung Woon Kim, Hyun Ha Chang, In Kyung Jung, Jeong Taek Woo, In Myung Yang, Jin Woo Kim, Soung Seol Kim, Young Kil Choi
Abstract
Background
Goiter has been a common problem in the thyroid disease. The exact mechanism of goiter had not been clarified yet, but some goiters were increased with TSH(thyrotropin releasing hormone) dependent manner. TSH might be a major influencing factor for increasing size of goiter(goitrogen) and theres many cofactors those influenced to goiter size. One of the rnost prominent growth factor as a goitrogen is a IGF-I(insulin-like growth factor-I). IGF-I play a great role as a cofactor of goitrogen with TSH. This study, therefore, is aimed to investigate intracellular activation of IGF-I gene promoter in the surgical specimens of thyroid tumor. Methods: We used surgical specimen of various thyroid tissues from normal to malignant along its cell nature. Actually we used normal liver tissue as a IGF-I control tissue, normal thyroid, benign adenoma, and papillary thyroid cancer tissue with its malignat nature. We checked Mrna expression of whole IGF-I and IGF-I exon 6 by Northern blot method, and IGF-I, promoter 1 expression by RT-PCR-transcription method. Autoradiographied signals were analysed with densitometer. Results: We found whole IGF-I mRNAs were expressed with alternate splicing in exon 1, 2 and exon 4, 5 respectively. Striking events of IGF-I transcription were multiple tranascription initiatian in Pl and P2, and 3 sites for polyadenylation in exon 6. Four or more Mrna bands in Northern blot analysis of IGF-I(0.8, 1.4, 4.2, and 7.8kb) were noted. In low molecular weight IGF-I Mrna did not change their signal intensity with tissues, but exan 6(7.8kb) signals were significantly increased to its hepatic expression levels in malignant tissue. IGF-I, exon 1 expression by RT-PCR-T7 transcription was strikingly increased in thyroid cancer tissue, but exon 6 expression was not a great expession. Conclusion: One possible guess for this expression discrepancy of each exon may be originated from different Mrna degradation of each IGF-I signals. We need more preeise experiment for Mrna degradation speed of IGF-I.
Key Words: IGF-I mRNA, Thyroid tissues


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