Fig. 7.

Coordinated transposon repression in GCs of the human fetal testis. (A) (Top) Summary of the expression pattern of PIWI-piRNA pathway components and L1 protein in developing germ cells in the human fetal testis at indicated timepoints and in aged xenograft samples. (Bottom) Relationships between L1 expression (protein, except where indicated) and expression of PIWI-piRNA pathway factors and H3K9me3 at indicated developmental stages. By GW22, many L1-expressing AGCs also express components of the repression network. (B) Model for transposon expression and repression in developing AGCs. See Discussion for details.