Mutation of conserved ETS motif or deletion of the composite element reduces intron 5 enhancer activity. Luciferase activity from exon 1 preceded by the wild-type intron 5 enhancer set and exon 1 preceded by the intron 5 enhancer containing either the 28 base deletion seen in patient 6.II.1 or the ETS motif C>T point mutation seen in patients 4.II.1, 11.II.1, 25.I.1, and 28.I.1. ***P < .001.