Fig. 4. Smads expression in postnatal testis and in PGCs. (A) Frozen sections from testes at 7 dpn were analyzed by immunofluorescence for the expression of Smad4 and Smad8, which shows ubiquitous immunostaining. (B) Frozen sections from testes at 4 and 7 dpn mice, (C) from 12.5 dpc fetal testis (200x magnification) and from 10.5 dpc genital ridges were analyzed for Smad5 expression, which shows a nuclear immunostaining pattern only in the germ cell compartment (arrowheads point to germ cells, within the seminiferous tubules or within the genital ridge; 400x magnifications).