Differential expression of divalent metal transporter DMT1 (Slc11a2) in the spermatogenic epithelium of the developing and adult rat testis.

Abstract

Iron is essential for male fertility, and disruptions in iron balance lead to impairment of testicular function. The divalent metal transporter DMT1 is a key modulator of transferrin- and non-transferrin-bound iron homeostasis. As a first step in determining the role of DMT1 in the testis, we have characterized the pattern of DMT1 expression in the developing and adult rat testis. Northern blot analysis and RT-PCR of testis polyadenylated RNA revealed the presence of iron-responsive element (IRE) and non-IRE transcripts. Semiquantitative immunoblotting of immature and adult rat testis uncovered the expression of two distinct DMT1 protein species. Immunohistochemistry showed that DMT1 was widespread throughout each seminiferous tubule and was expressed in the intracellular compartment. In the adult rat testis, DMT1 was immunolocalized to both the Sertoli and germ cells. In contrast to the immature testis, expression was dependent on the stage of the spermatogenic cycle. DMT1 was not detected on any plasma membranes in either the developing or the adult testis, suggesting that DMT1 is not primarily responsible for translocating iron across this epithelium. Our data suggest an important role for DMT1 in intracellular iron handling during spermatogenesis and imply that germ cells have a need for a precisely targeted and timed supply of iron. We suggest that DMT1 may, as it does in other tissues, play a role in transporting iron between intracellular compartments and thus may play an important role in male fertility.