STXBP1 and dentin dysplasia: The smallest region of deletion overlap affects only two coding genes, RALGPS1 and GARNL3 and is localized in close proximity to the known ID / epilepsy gene STXBP1. The seizure, ID, and DD phenotype in the deletions described here is at least partly independent from STXBP1, as shown by microdeletion sizes and expression studies.