Increased IGF-II protein affects p57kip2 expression in vivo and in vitro: implications for Beckwith-Wiedemann syndrome.
In both human and mouse, the Igf2 gene, localized on chromosomes 11 and 7, respectively, is expressed from the paternally inherited chromosome in the majority of tissues. Insulin-like growth factor-II ( IGF-II) plays an important role in embryonic growth, and aberrant IGF2 expression has been documented in several human pathologies, such as Beckwith-Wiedemann syndrome (BWS), and a wide variety of tumors. Human and mouse genetic data strongly implicate another gene, CDKN1C (p57(kip2)), located in the same imprinted gene cluster on human chromosome II, in BWS. p57(KIP2) is a cyclin-dependent kinase inhibitor and is required for normal mouse embryonic development. Mutations in CDKN1C (p57(kip2)) have been identified in a small proportion of patients with BWS, and removal of the gene from mice by targeted mutagenesis produces a phenotype with elements in common with this overgrowth syndrome. Patients with BWS with biallelic expression of IGF2 or with a CDKN1C (p57(kip2)) mutation, as well as overlapping phenotypes observed in two types of mutant mice, the p57(kip2) knockout and IGF-II-overexpressing mice, strongly suggest that the genes may act in a common pathway of growth control in situations where Igf2 expression is abnormal. Herein, we show that p57(kip2) expression is reduced on IGF-II treatment of primary embryo fibroblasts in a dose-dependent manner. In addition, p57(kip2) expression is down-regulated in mice with high serum levels of IGF-II. These data suggest that the effects of increased IGF-II in BWS may, in part, be mediated through a decrease in p57(kip2) gene expression.[1]References
- Increased IGF-II protein affects p57kip2 expression in vivo and in vitro: implications for Beckwith-Wiedemann syndrome. Grandjean, V., Smith, J., Schofield, P.N., Ferguson-Smith, A.C. Proc. Natl. Acad. Sci. U.S.A. (2000) [Pubmed]
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