The gene for insulin-like growth factor-binding protein-1 is localized to human chromosomal region 7p14-p12

Genes, fat intake, and cardiovascular disease risk factors in the Quebec Family Study

OBJECTIVE

The aim of this study was to assess gene-diet interaction effects on cardiovascular disease (CVD) risk factors (waist circumference, plasma triacylglycerol, high-density lipoprotein-cholesterol and fasting glucose concentrations, and diastolic and systolic blood pressure) in the Quebec Family Study cohort.

DESIGN

Sixty-four polymorphisms from 45 candidate genes were studied in 645 subjects. Dietary fat intake was obtained from a 3-day weighted food record.

RESULTS

We observed 18 significant interactions at a p value <or= 0.01. Among them, the Pro12Ala polymorphism in peroxisome proliferator-activated receptor gamma, alone or in interaction with fat intake, significantly modulated waist circumference (p = 0.0005 for both effects). Additionally, the apolipoprotein E genotype in interaction with fat intake was significantly associated with diastolic and systolic blood pressure (p = 0.01 and p = 0.001, respectively). The ghrelin Leu72Met polymorphism also interacted with dietary fat in its relation to waist circumference and triacylglycerol concentrations (p = 0.0004 and p = 0.005).

DISCUSSION

These results suggest that several alleles at candidate genes interact with dietary fat intake to modulate well-known CVD risk factors. The identification of gene-diet interaction effects is likely to provide useful information concerning the etiology of CVD.

Conservation of IGFBP structure during evolution: cloning of chicken insulin-like growth factor binding protein-5

The insulin-like growth factor binding proteins (IGFBPs) have conserved characteristics of their genomic organization, including similar locations of exon borders relative to nucleotides encoding conserved cysteine residues. Furthermore, the human IGFBP genes, as well as the human homeobox (HOX) genes, are localized to chromosomes 2, 7, 12, and 17. Although little is known about the evolution of the IGFBP genes, the association of human IGFBP and homeobox (HOX) genes at four chromosomal loci may indicate that their ancestral genes were linked prior to the first duplication of chromosomal DNA containing the ancestral HOX cluster. The hypothesis that IGFBPs are ancient proteins is supported by the reported detection of IGFBP activity in serum from the Agnathan species, Geotria australis, a primitive vertebrate. Further studies of IGFBPs in different species are needed to understand the evolution of this protein/gene family. Chicken provides a good intermediate model, since birds diverged from mammals approximately 300 million years ago. A complementary DNA (cDNA) clone encoding chicken insulin-like growth factor binding protein-5 (cIGFBP-5) was isolated. The deduced amino acid sequence is 83% identical to human IGFBP-5 and encodes a mature polypeptide of 251 amino acids. The conservation of IGFBP-5 primary structure across vertebrate species suggests maintenance of important functions during evolution.

Insulinlike growth factors and binding proteins in colon cancer

Insulinlike growth factors (IGFs) express anabolic and mitogenic activity on wide variety of cells. Besides endocrine effects, IGFs have major autocrine and paracrine effects on many cellular functions. Two factors that significantly affect the extent of cellular response to IGFs include the membrane receptors for IGFs and the soluble binding proteins (BPs), which modulate the action of IGFs at the receptor level. IGFs, IGF receptors, and IGFs and their BPs (IGF-BPs) thus constitute three components of the IGF system. A role of IGFs in the transformation and proliferation of cancer cells has become increasingly evident in the past few years. Studies from several laboratories show that all three components of the IGF system may play an important role in the proliferation of colon cancers. It was recently shown that the relative expression of IGFs and IGF/BPs may critically control the metastatic potential of colon cancers. The purpose of this article is to summarize our current knowledge of the IGF system and to present support for a significant role of IGFs in the initiation and growth of colon cancers. The expression and structural aspects of IGFs, their receptors, and BPs are outlined first, followed by a discussion of the role of IGFs in gastrointestinal functions and in colon cancers.

Evolution of EF-hand calcium-modulated proteins. V. The genes encoding EF-hand proteins are not clustered in mammalian genomes

The chromosomal assignments of genes belonging to the EF-hand family which have a common origin are compiled in this article. So far data are available from 27 human gene loci belonging to 6 subfamilies and 8 murine loci belonging to 4 subfamilies. Chromosomal localization has been obtained by somatic-cell hybrid analysis using the Southern blot technique or PCR amplification, metaphase spread in situ hybridization, or isolation of the particular genes from chromosome-specific libraries. Except for genes of the S-100 alpha proteins which are grouped on human chromosome 1q12-25 and mouse chromosome 3, no linkage has been found for genes encoding EF-hand proteins, indicating absence of selective pressure for maintaining chromosomal clustering. Six of these genes map to known syntenic groups conserved in the human and mouse genomes. This suggests that chromosomal translocations occurred before divergence of these species. The possible significance of chromosomal positioning with respect to nearby located known genes and genetic disease loci is discussed.

The genes for the highly homologous Ca(2+)-binding proteins oncomodulin and parvalbumin are not linked in the human genome

The chromosomal loci of the human parvalbumin and oncomodulin single-copy genes that encode structurally and evolutionarily closely related Ca(2+)-binding proteins were determined by somatic cell hybrid analysis. Southern blot analysis of genomic DNA from 25 human-hamster somatic cell hybrids showed that the human gene for oncomodulin resides on chromosome 7. Analysis of human-mouse hybrids selectively retaining human chromosome 7 or a portion of it allowed specific assignment of the gene locus to the p11-p13 region of chromosome 7 known to be mutated or deleted in patients with the Greig cephalopolysyndactyly syndrome. By gene dosage analysis on Southern blots, we showed that the gene for human parvalbumin maps distally to the cat eye syndrome marker D22S9 on chromosome 22q. Using somatic cell hybrids containing parts of human chromosome 22, the parvalbumin gene was sublocalized to the region 22q12-q13.1. This region contains a linkage group that maps to mouse chromosome 15, region E, and includes the SIS, ARSA, and DIA 1 genes. Our findings are consistent with the recent localization of the mouse parvalbumin gene to this region by two independent methods (C. H. Zühlke et al., 1989, Genet. Res. 54:37-43; S. Adolph et al., 1989, Cytogenet. Cell Genet. 52:177-179).

Contiguous localization of the genes encoding human insulin-like growth factor binding proteins 1(IGBP1) and 3(IGBP3) on chromosome 7

In extracellular fluids the insulin-like growth factors (IGFs) are bound to specific binding proteins (IGBPs). The genes for two members of this protein family have been mapped, the IGBP1 gene to human chromosomal region 7p14-p12 and the IGBP2 gene to region 2q33-q34. In this study, somatic cell hybrid analysis indicated that IGBP3 is also located on chromosome 7. Pulsed-field gel electrophoresis was used to demonstrate the close physical linkage between IGBP1 and IGBP3. Overlapping cosmid clones encompassing these genes were isolated, and restriction endonuclease mapping showed that the genes are arranged in a tail-to-tail fashion separated by 20 kb of DNA. Further characterization of the IGBP1 DNA sequence disclosed a duplication of the intron 3-exon 4 junction within the third intron. In addition, we report RFLPs for ApaLI and TaqI in the IGBP1 locus.

Structure and localization of the human insulin-like growth factor-binding protein 2 gene

Insulin-like growth factor binding proteins (IGFBPs) are extracellular proteins that specifically bind IGF and modulate their effects. The human IGFBP2 gene was studied and shown to be localized to chromosome 2 region q33-q34, by somatic cell hybrid analysis and in situ hybridization. Structural characterization of the gene showed that it consists of four exons with three introns of lengths 27.0, 1.0, and 1.9 kilobase-pairs. Comparison of the encoded protein sequence of each exon in IGFBP1, 2, and 3 reveals the highest amino acid identity, 28%, in exon 1, while the lowest was found in exon 2. However, pairwise sequence comparisons demonstrate 50% identity between the protein sequences encoded by exon 4 in IGFBP1 and 2, while their respective identities with IGFBP3 are only 25 and 30%.

Sequence analysis, expression and chromosomal localization of a gene, isolated from a subtracted human retina cDNA library, that encodes an insulin-like growth factor binding protein (IGFBP2)

The metabolic functions of insulin-like growth factors (IGFs) I and II are modulated by a family of binding proteins which are present in biological fluids and are synthesized by a variety of cell types. A cDNA clone, isolated at random from a subtracted human retina library, has been identified to code for a novel IGF-binding protein (IGFBP2) by its sequence homology to the peptide sequence of IGF binding proteins purified from bovine MDBK and rat BRL-3A cells. The complete nucleotide sequence of the IGFBP2 cDNA is 1406 bp long, contains 66% G-Cs and an open reading frame of 328 amino acids with a putative signal or pro-peptide of 39 residues. The mature polypeptide of 289 amino acids has 18 cysteines, a putative ATP-binding site and an RGD tripeptide. The 1.4 kb IGFBP2 transcript is expressed in several human tissues including fetal eye and fetal brain, but not in the human lymphoblastoid cell line against which the retinal cDNA library was subtracted. In situ hybridization to sections of mouse retina localized the mRNA for IGFBP2 primarily in the outer nuclear layer of photoreceptors. Southern blot analysis of DNA from human x rodent and mouse x rodent somatic cell hybrids assigned the gene for IGFBP2 to human chromosome 2q33-qter and mouse chromosome 1 in a known conserved syntenic region.

Identification and molecular characterization of insulin-like growth factor binding proteins (IGFBP-1, -2, -3, -4, -5 and -6)

Six different insulin-like growth factor binding proteins (IGFBPs) have been identified by molecular cloning of their cDNAs from rat and human tissues and designated as IGFBP-1, -2, -3, -4, -5 and -6. The total number of amino acid residues for the mature rat BPs ranges from 201 for IGFBP-6 to 270 for IGFBP-2, while the human homologs range from 216 for IGFBP-6 to 289 for IGFBP-2. Except for IGFBP-6, all rat and human IGFBPs contain 18 homologous cysteines; twelve are located at the N-terminal and span approximately one-third of the total amino acid sequence, while the remaining six are distributed at the C-terminal and span the last one-third of the protein sequence. Both rat and human IGFBP-4 possess two extra cysteines at the mid-region of the molecule. By contrast, rat and human IGFBP-6 contain only 14 and 16 cysteines, respectively. Absence of the two and four cysteines in the N-terminal region in the human and rat IGFBP-6 resulted in the deletion of the invariant Gly-Cys-Gly-Cys-Cys sequence which is present in all the other five IGFBPs. Both rat and human IGFBP-3 possess multiple N-linked glycosylation sites at the mid-region of the molecule, which accounts for their apparent molecular size being larger than the calculated molecular weight, based on the amino acid sequence. One potential N-linked glycosylation site is located at the mid-region of rat and human IGFBP-4, whereas only human but not rat IGFBP-6 possesses one N-linked glycosylation site at the extreme C-terminal of the molecule. An RGD sequence is found in the C-terminal of IGFBP-1 and -2. In this short review, updated information on the structural identification and molecular cloning of the six IGFBPs will be presented. In addition, the potential regulation of the BPs at the transcriptional and translational levels will be discussed.