PITX1 and Brachydactyly - elbow wrist dysplasia: Moreover, we also introduced Pen 7.7 kb upstream of the Pitx1 promoter (Pitx1EGFP;ΔPen;Rel3/EGFP;ΔPen;+: Pitx1EGFP;ΔPen;Rel3), in a similar genetic distance (10.5 kb enhancer-promoter distance) as the one found in the most severe case of Liebenberg syndrome described (Fig. 2C, Supplementary Fig. 1)15.