In terms of the clinical and biochemical phenotype of 3-M syndrome, we have demonstrated that i) 3-M children with mutations in CUL7 are significantly shorter than those with either OBSL1 or CCDC8 mutations (Hanson et al. 2012), ii) there is clinical evidence of GH and/or IGF1 resistance (Hanson et al. 2012), iii) associated with this, growth factor signalling in exvivo 3-M fibroblast cells is disrupted (Hanson et al. 2012), and iv) IGF2 expression and IGF2 secreted from 3-M fibroblasts is very low (Murray et al. 2013). Here, OBSL1 is linked to 3M syndrome.