Building on this, a de novo p.Gly77Arg variant of GNB2, identified by exome sequencing, was associated with a phenotype that was similar to a pathogenic variant of its homologue, GNB1. The global developmental delay and hypotonia that is a feature of these patients may overlap with those manifesting disease associated with GNB1 variants [55]. This evidence concerns the gene GNB1 and Global developmental delay.