Disruption of the imprinted Grb10 gene leads to disproportionate overgrowth by an Igf2-independent mechanism

Abstract

To investigate the function of the Grb10 adapter protein, we have generated mice in which the Grb10 gene was disrupted by a gene-trap insertion. Our experiments confirm that Grb10 is subject to genomic imprinting with the majority of Grb10 expression arising from the maternally inherited allele. Consistent with this, disruption of the maternal allele results in overgrowth of both the embryo and placenta such that mutant mice are at birth Ϸ30% larger than normal. This observation establishes that Grb10 is a potent growth inhibitor. In humans, GRB10 is located at chromosome 7p11.2-p12 and has been associated with Silver-Russell syndrome, in which Ϸ10% of those affected inherit both copies of chromosome 7 from their mother. Our results indicate that changes in GRB10 dosage could, in at least some cases, account for the severe growth retardation that is characteristic of Silver-Russell syndrome. Because Grb10 is a signaling protein capable of interacting with tyrosine kinase receptors, we tested genetically whether Grb10 might act downstream of insulin-like growth factor 2, a paternally expressed growth-promoting gene. The result indicates that Grb10 action is essentially independent of insulinlike growth factor 2, providing evidence that imprinting acts on at least two major fetal growth axes in a manner consistent with parent-offspring conflict theory.adapter protein ͉ cell signaling ͉ genomic imprinting ͉ growth factor receptor-bound protein ͉ insulin-like growth factor

The RASSF8 candidate tumor suppressor inhibits cell growth and regulates the Wnt and NF-κB signaling pathways

“…Mouse mRNA in situ hybridization In situ hybridization was carried out on E15.5 embryos and adult mouse tissues sections using sense and antisense probes as previously described (Charalambous et al, 2003). The probes for RASSF8 were generated from a mouse Rassf8 containing pCRbluntII-topo vector (image clone: 40105476) using a T7 promoter (sense strand) or SP6 promoter (antisense) following digestion with EconI or PstI enzymes, respectively.…”

Grb10 characterization in bovine cumulus oocyte complexes from different follicle sizes

“…Also, the disruption of Grb10 maternal allele gene caused an overgrowth in mice at birth (CHARALAMBOUS et al, 2003) and in adult rats (WANG et al, 2007). Therefore, this failure in embryonic development may be due to lack of accumulated Grb10 mRNA and protein in female gamete.…”

Frequency and characterization of DNA methylation defects in children born SGA

“…Disruption of the maternal allele leads to overgrowth of placenta and embryo with the mutant mice being B30% larger than the wild-type mice. 36 Moreover GRB10 has long been proposed as responsible candidate gene for Silver-Russell syndrome in maternal uniparental disomy for chromosome 7 and maternal duplication of the chromosomal region 7p11.2-p12. 37,38 However, exclusion of causative mutations in GRB10 in patients with Silver-Russell syndrome and the identification of patients with segmental maternal uniparental disomy restricted to the long arm of chromosome 7 make a relevant role of GRB10 in patients with SilverRussell syndrome unlikely.…”