Smad4 overexpression causes germ cell ablation and leydig cell hyperplasia in transgenic mice. Related Articles Smad4 overexpression causes germ cell ablation and leydig cell hyperplasia in transgenic mice. Am J Pathol. 2002 Nov;161(5):1723-34 Authors: Narula A, Kilen S, Ma E, Kroeger J, Goldberg E, Woodruff TKOriginal Article