ARHGEF39 and Delayed speech and language development: Theseproteins act as molecular switches to regulate diverse processes includingtranscriptional regulation, cell migration, cell growth and dendriticdevelopment.58, 59, 60 Other members of thisfamily have previously been implicated in language impairment(ARHGEF19),29intellectualdisability (ARHGEF6)61 andmoderate intellectual disability with speech delay (ARHGEF9).4 Future studies into the expression pattern and function ofthis gene may reveal a potential role for ARHGEF39 in the development oflanguage relevant circuitry in the brain.