Human GRB 10 on chromosome 7 , a homologue of the mouse imprinted gene Grb 10 , is a candidate , because GRB 10 has a suppressive effect on growth , through its interaction with either the IGF 1 receptor or the GH receptor , and two patients with RSS were shown to have a maternally derived duplication of 7p11 p 13 , encompassing GRB 10 . ^^^