Localization of insulin-like growth factor genes to human chromosomes 11 and 12

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Abstract
The insulin-like growth factors IGF-I and IGF-II are required for growth and development1–4. Both are single-chain proteins (of 70 and 67 amino acids respectively) derived from precursors by proteolytic processing5–6. IGF-I may be particularly important in promoting normal stature7 and IGF-II may be a fetal growth hormone8. The IGF proteins are probably synthesized by many normal tissues9 and by some tumours10. The secretion of growth factors by tumours and tumour-derived cell lines suggests that they may act as autocrine regulators of cell proliferation11. Because of the possible role of these proteins in growth disorders and cancer, and their sequence homology with insulin, we have determined their chromosomal localization. Using somatic cell hybrids12 and cloned cDNA probes6 for these proteins, we have assigned the genes for IGF-I and IGF-II to human chromosomes 12 and 11, respectively. We present evidence that the IGF-II gene is located on the short arm of chromosome 11 with a ras protooncogene and the insulin structural gene, and also suggest the existence of a fragment length polymorphism using the IGF-I probe.