Lack of association between insulin-like growth factor-I (IGF-I) gene polymorphism (rs35767) and power performance in professional, amateur athletes and non-athlete individuals in Iranian population

Growth hormone (GH) regulates insulin-like growth factor-I (IGF-I) gene expression through signal transducer and activator of transcription 5b (STAT5b) and STAT5a. The objective of this study was to identify the cis-regulatory DNA region involved in this process. By cotransfection analyses of shotgun DNA fragments of a bacterial artificial chromosome sequence containing the entire human IGF-I gene and a large 5'-flanking region, a approximately 700-bp DNA region approximately 75 kb 5' to the IGF-I gene was found to have the ability to enhance gene expression from both heterologous and homologous promoters in the presence of constitutively active STAT5a or STAT5b. This 700-bp DNA region contains two closely located consensus STAT5-binding sites, and its sequence appears to be evolutionarily conserved. Electrophoretic mobility shift assays verified the ability of the two putative STAT5-binding sites to bind to STAT5a and STAT5b. Cotransfection analyses confirmed that both STAT5-binding sites were necessary for the 700-bp DNA region to mediate STAT5a or STAT5b activation of gene transcription. Chromatin immunoprecipitation assays demonstrated that the chromosomal region containing these two STAT5-binding sites was bound by constitutively active STAT5b protein in HepG2 cells and that the binding was accompanied by increased expression of IGF-I mRNA. In reconstituted GH-responsive cells, this 700-bp DNA region was able to mediate GH-induced STAT5a or STAT5b activation of gene expression. These results together suggest that this STAT5-binding site-containing distal 5'-flanking region of IGF-I gene may be an enhancer mediating GH-induced STAT5 activation of IGF-I gene transcription.

We have characterized a second nonallelic insulin-like growth factor-I (IGF-I) gene in the chum salmon (Oncorhynchus keta) genome. This gene, IGF-I.2, differs from the previously described chum salmon IGF-I gene, IGF-I.1, in the E peptide-coding portion of exon 3; specifically, the IGF-I.2 gene lacks one codon present in the IGF-I gene and contains two potential splice donor sites at the 3' end of exon 3 rather than the single, more distal site present in the IGF-I.1 gene. The expression of these two IGF-I genes could give rise to as many as six IGF-I mRNA species, each of which would encode a unique E-peptide moiety of the IGF-I prohormone. Thus, the presence of multiple, distinct IGF genes adds an additional level of complexity to IGF-I gene expression and IGF-I biosynthesis in salmon.

Developmental regulation of insulin-like growth factor-I and growth hormone receptor gene expression

Molecular genetic selection on individual genes is a promising method to genetically improve economically important traits in chickens. The insulin-like growth factor-I (IGF-I) gene may play important roles in growth of multiple tissues, including muscle cells, cartilage and bone. In the present study, polymorphism of the promoter and 5' untranslated region of IGF-I gene of Mazandaran native fowls was investigated. In order to evaluate the IGF-I gene polymorphism, we used the restriction fragment length polymorphism (RFLP) method. Blood samples were collected from randomly chosen 100 Mazandaran native fowls. Genomic DNA was extracted using modified salting-out method and amplified polymerase chain reaction technique. The promoter and 5' untranslated region of the fowl IGF-I gene was amplified to produce a 621 bp fragment. The PCR products were electrophoresed on 2.5% agarose gel and stained by ethidium bromide. Then they were digested of amplicons with PstI, which revealed two alleles A and B. Data were analyzed using Pop Gene 32 software package. In this population, AA, AB, BB genotypes were identified with 25.88, 50.23 and 23.89% frequencies, respectively. Allele frequencies (A and B) were 0.51 and 0.49, respectively. The Chi-square (χ 2 ) test did not show deviation from Hardy–Weinberg equilibrium (P<0.05).

Growth rate is one of the economically important quantitative traits that affect carcass quantity in beef cattle. Two genes, bovine insulin-like growth factor I (IGF-I) and myogenic factor 5 (MYF5), were chosen as candidate genes for growth traits due to their important role in growth and development of mammals. The objectives of this study were to determine gene-specific single nucleotide polymorphism (SNP) markers of the IGF-I and MYF5 positional candidate genes and to investigate their associations with growth traits in Korean cattle. Genotyping of the SNP markers in these candidate genes was carried out using the single strand conformation polymorphism (SSCP) analysis. The frequencies of A and B alleles were 0.72 and 0.28 for IGF-I gene and 0.39 and 0.61 for MYF5 gene, respectively, in Korean cattle population examined. The gene-specific SNP marker association analysis indicated that the SNP genotype in IGF-I gene showed a significant association (p<0.05) with weight at 3 months (W3), and cows with AB genotype had higher W3 than BB genotype cows. The SNP genotype of MYF5 gene was found to have a significant effect (p<0.05) on the weight at 12 months (W12) and average daily gain (ADG), and cows with BB and AB genotypes had higher W12 and ADG compared with cows with AA genotype, respectively. However, no significant association between the SNP genotypes and any other growth traits was detected. The gene-specific SNP markers in the IGF-I and MYF5 candidate genes may be useful for selection on growth traits in Korean cattle. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 8 : 1061-1065)

The effects of cortisol on hepatic GH receptor and insulin-like growth factor-I (IGF-I) gene expression were investigated in sheep fetuses during late gestation and after experimental manipulation of plasma cortisol levels by fetal adrenalectomy and exogenous infusion of cortisol. Hepatic GH receptor and IGF-I messenger RNA (mRNA) levels increased with increasing gestational age in parallel with the normal rise in fetal cortisol levels toward term (145 +/- 2 days). These increases in mRNA abundance toward term were prevented when the prepartum cortisol surge was abolished by fetal adrenalectomy and were stimulated prematurely in fetuses younger than 130 days by exogenous infusion of cortisol. Both the class 1 and class 2 transcripts of the IGF-I gene were increased when cortisol levels were elevated either endogenously or exogenously. However, there were no significant changes in fetal plasma IGF-I levels either with increasing gestational age or in response to experimental manipulation of the fetal cortisol level. When the data from all the fetuses were combined irrespective of treatment or gestational age, there were significant positive correlations between the log plasma cortisol concentration in utero and the abundance of GH receptor and IGF-I mRNA in the fetal liver. There was also a significant inverse relationship between log plasma cortisol and the ratio of class 1 to class 2 transcript abundance in the fetal liver. These findings show that cortisol is a physiological regulator of hepatic GH receptor and IGF-I gene expression in fetal sheep during late gestation and indicate that it preferentially increases the class 2 transcript of the IGF-I gene. The prepartum cortisol surge therefore appears to have an important maturational role in initiating the perinatal switch from the fetal to adult modes of somatotrophic regulation.

Identification of multiple transcription start sites in the human insulin-like growth factor-I gene

Immunolocalization and expression of insulin-like growth factor I (IGF-I) in the mammary gland during rat gestation and lactation

The possible involvement of the protein kinase C (PKC) pathway in transcriptional regulation of the human insulin-like growth factor-I (IGF-I) gene has been suggested. In this study, we sought to determine whether a PKC-dependent pathway is implicated in the transcriptional control, and if it is, how this occurs. Treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) caused an increase in the activity of the human IGF-I gene major promoter in HepG2 cells. A CCAAT/enhancer-binding protein (C/EBP) binding site located at +22 to +30 was bound by C/EBP beta in a TPA-dependent manner and was solely responsible for the TPA responsiveness. This increase in C/EBP beta activity occurs through transcriptional and posttranslational regulation, and the latter is mediated by activation of p90 ribosomal S6 kinase (RSK): co-expression of dominant negative RSK abolished the TPA-responsive and C/EBP beta-dependent transactivation. Also, TPA-responsive activation of GAL4-C/EBP beta chimera required the Ser residue known as the RSK target. In SK-N-MC cells, which display constitutive, high expression of IGF-I on use of the major promoter, a large amount of C/EBP beta binding was observed with the C/EBP site in the basal state. Treatment with PKC inhibitors substantially reduced the promoter activity and mRNA amounts of IGF-I, with the binding of C/EBP beta to the C/EBP site also being reduced. When the C/EBP site was disrupted, the basal promoter activity was reduced, but the reduction by the PKC inhibitor was no longer observed. These observations suggest that the increase of C/EBP beta binding to the C/EBP site, which is in part mediated via activation of RSK, can primarily explain the TPA responsiveness of the IGF-I gene promoter. The intrinsic PKC activity in SK-N-MC cells should play a major role in the constitutive, high expression of IGF-I and may therefore contribute in part to the maintenance of the tumor phenotype of the cells.

Molecular analysis is an easier means to identify desirable genotypes for growth. Candidate gene (s) for growth trait like insulin like growth factor (IGF) has imperative function for growth, body composition, fat deposition, metabolic and skeletal traits and the molecular genetic selection on individual genes is a very efficient method to genetically improve economically important traits in chickens. In the present study, polymorphism of the promoter and 5' untranslated region of IGF-I gene of nativeAseel, was investigated. In order to evaluate the IGF-I gene polymorphism, we used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Feather samples were collected at random from 50 Aseel chickensof Pakistan. Genomic DNA was extracted using modified salting-out PCI (Phenol: Chlorophorm: Iso-amylacohol) method and amplified by polymerase chain reaction. The promoter and 5' untranslated region of the IGF-I gene was amplified to produce a 621 bp fragment. The PCR products were electrophoresed on 2.5% agarose gel and stained by ethidium bromide and then finally on confirmation of amplification the ampliconswere digested Hinf-I restriction enzyme and this revealed two alleles A and B having all three combinations of genotypes i.e. AA, AB were found. Data were analyzed using Pop Gene 3.1 software package. Allele frequencies (A and B) were 0.53 and 0.47 while genotypic frequency fo AB (66) was significantly higher than AA (20) and AB (66). The Chi-square (χ2) test did not show any deviation from Hardy–Weinberg equilibrium.

The research was aimed is to detect Insulin-like growth factor-I (IGF-I) gene polymorphism and their effect on growth traits in Indonesia natives chicken. Seventy two Indonesian native chicken are going to be used in this research. The polymorphism of IGF-I gene was detected by PCR-RFLP/Pst-I. Four growth traits (body weight at 1, 2, 3, and 4 months) were recorded for analyzing the association between IGF-I gene polymorphism and growth performance.The results showed that allele A (621 bp) and allele B (364 and 257 bp) were found in this research. It was found that Indonesian native chicken carried high frequencies of allele A (0.82), and frequencies of IGF-I genotypes (AA, AB, BB) were 68.0, 27.8, and 4,2%, respectively. When compared to the IGF-I genotypes, the BB genotype had the highest body weight at 1, 2, 3, and 4 month (P0.05). The results showed that the B allele was positive of associated to a higher growth rate. Therefore, these results suggest that there is a possibility of IGF-I genotypes acting as a molecular marker for growth rate of Indonesia native. Key words: Polymorphism, IGF-I, Polecular Marker, Growth, Indonesia Native

Insulin-like growth factor-I genotype and birthweight

The polymorphism of insulin-like growth factor-I (IGF-I) gene was examined in Japanese postmenopausal women to analyze the genetic background for osteoporosis. In this study, the dinucleotide (cytosine-adenine; CA) repeat sequence lying upstream of the transcription initiation site of this gene was examined. We named the most frequent allele including (CA) 19 as J allele. There were 6 alleles (J-4 containing 17 CA repeats: (CA)17, [J-2 (CA)18, J (CA)19, J + 2 (CA)20, J + 4 (CA)21, J + 6 (CA)22]) in the Japanese population. The genotype distribution was different from that of Caucasians. There was no different in bone mineral density (BMD) between the group with one or two alleles of each genotype and that without that genotype. When we separate the subjects into three groups having two alleles, one allele, and no alleles, the three subjects who possess the allele 'J-2' in both strands had low BMD (Z score of L2-4; -1.24 +/- 0.56, total body; -0.943 +/- 0.59, mean +/- SE). On the other hand, sequence of IGF-I gene in this study was different from reported sequence of IGF-I gene; that was 2 base pair (bp) deletion following 3'end of CArepeat (-645adenine/-646guanine). The present study showed that there was no association between the microsatellite polymorphism of IGF-I gene and BMD in Japanese postmenopausal women, but some possibility remains that the microsatellite polymorphism of IGF-I gene is useful to detect a kind of particular osteoporosis.

The human IGF-I gene contains two cell type-specifically regulated promoters

The insulin-like growth factor-I (IGF-I) gene was analyzed in a population of children with growth disorders presenting normal GH and low IGF-I. We thus tried to detect any mutation in the IGF-I gene that could be responsible for short stature in children, using PCR, single-strand conformation polymorphism (SSCP) analysis, followed by DNA cloning and sequencing. We demonstrated in all examined children significant changes in the promoter region of the IGF-I gene (P1 IGF-I). Nucleotide sequence changes, such as CC-->GT and A-->G, and their localization are described. The results obtained excluded mutations in the coding sequence of the IGF-I gene. We conclude that testing the IGF-I P1 region, using PCR/SSCP analysis, could be useful in the diagnosis of growth disorders.