Organ-Specific and Age-Dependent Expression of Insulin-like Growth Factor-I (IGF-I) mRNA Variants: IGF-IA and IB mRNAs in the Mouse

Abstract

-Insulin-like growth factor-I (IGF-I) gene generates several IGF-I mRNA variants by alternative splicing. Two promoters are present in mouse IGF-I gene. Each promoter encodes two IGF-I mRNA variants (IGF-IA and IGF-IB mRNAs). Variants differ by the presence (IGF-IB) or absence (IGF-IA) of a 52-bp insert in the E domain-coding region. Functional differences among IGF-I mRNAs, and regulatory mechanisms for alternative splicing of IGF-I mRNA are not yet known. We analyzed the expression of mouse IGF-IA and IGF-IB mRNAs using SYBR Green real-time RT-PCR. In the liver, IGF-I mRNA expression increased from 10 days of age to 45 days. In the uterus and ovary, IGF-I mRNA expression increased from 21 days of age, and then decreased at 45 days. In the kidney, IGF-I mRNA expression decreased from 10 days of age. IGF-IA mRNA levels were higher than IGF-IB mRNA levels in all organs examined. Estradiol-17 β (E2) treatment in ovariectomized mice increased uterine IGF-IA and IGF-IB mRNA levels from 3 hr after injection, and highest levels for both mRNAs were detected at 6 hr, and relative increase was greater for IGF-IB mRNA than for IGF-IA mRNA. These results suggest that expression of IGF-I mRNA variants is regulated in organ-specific and age-dependent manners, and estrogen is involved in the change of IGF-I mRNA variant expression.

IGF1 mRNA isoform expression in the cervix of HPV-positive women with pre-cancerous and cancer lesions

“…Other studies have indicated that the locally acting iGF1 isoform also has neuroprotective effects and protects cardiomyocytes from hypertrophic and oxidative stress (9,23,24). Ohtsuki et al, using the pcr method, demonstrated that iGF1Ea mrna was more abundant than iGF1Eb mrna in a number of organs (uterus, ovary, liver and kidney) in the mouse, and was both organ specifically and temporally regulated (25). additionally, it has been suggested that E-peptides modulate the cell entry of mature iGF1 (26).…”

“…Recently, a number of studies have focused on the identification of different IGF1 isoforms and the evaluation of their functional significance (9,(20)(21)(22)(23)(24)(25)(26).…”

“…it has previously been suggested that E-peptides may have functions distinct from mature iGF1. Siegfried et al demonstrated that E-peptide derived from the iGF1Eb isoform exhibits mitogenic activity (25). later, it was shown that E-peptides increase IGF1 uptake into cells and enhance mature iGF1 activity (26).…”

Estradiol, Progesterone, and Transforming Growth Factor α Regulate Insulin-Like Growth Factor Binding Protein-3 (IGFBP3) Expression in Mouse Endometrial Cells

“…Estrogen stimulates Igf1 transcription (Murphy et al, 1987;Ghahary et al, 1990;Kapur et al, 1992;Zhou et al, 1994;Ohtsuki et al, 2005), and high levels of circulating estrogen at proestrus induced high Igf1 mRNA levels. Igf1r mRNA levels also changed during the estrous cycle; they were high at diestrus and low during proestrus and estrus, suggesting that the responsiveness of endometrial cells to IGF1 depends upon the stage of the estrous cycle, and possibly upon levels of estrogen and progestin.…”

Effects of Intestinal Microflora on Superoxide Dismutase Activity in the Mouse Cecum

“…The cDNA sequence was obtained from GenBank (accession number; NM_011434), and forward and reverse primers were designed to span different exons to avoid genomic DNA amplification. Quantitative measurement was performed by establishing a linear amplification curve from serial dilutions of cloned mouse CuZnSOD mRNA and GAPDH mRNA [21]. The amount of CuZn-SOD mRNA was normalized to the amount of GAPDH mRNA.…”