The remaining three genes—NFIX, GPC3, and BRWD3—encode a transcription factor, a proteoglycan, and a bromodomain-containing protein, respectively6, 31, 32 (23 case subjects, 3.2%). There is currently no clear functional link between these genes and the other genes we report here. However, it is possible that BRWD3 mutations also cause overgrowth through epigenetic regulation dysfunction, as there are data suggesting it is involved in histone H3.3 regulation.43