Figure 6.

Intracellular modulators of TGFβ superfamily signaling are differentially expressed in germ cells of the developing and adult mouse testis. Striking differences in the expression of the related Hgs and Zfyve9, Smurf1 and SMURF2 and Net25 and MAN1 were detected within germ and Sertoli cells between the first wave of spermatogenesis and in the cycling adult seminiferous epithelium. Selective modulation of responses to TGFβ superfamily ligands during differentiation may be endowed by regulated production of positive (HGS, ZFYVE9) and negative signaling (SMURF1, SMURF2, NET25, MAN1) regulators. Due to their individual capacities to modulate signal transduction, differential expression of these functionally related pairs may confer important switches in the cellular responses to TGFβ superfamily ligands. Lower panel: dotted line indicates expression pattern in germ cells during the first wave of spermatogenesis; solid line indicates expression in germ cells of the adult testis. Gon, gonocyte; spg,spermatogonium; spc, spermatocyte; RS, round spermatid; ES, elongating spermatid.