Tubulobulbar complexes (TBCs) are actin-related double-membrane invaginations 
formed at intercellular junctions in the seminiferous epithelium of mammalian 
testis. They occur at basal junction complexes between neighboring Sertoli cells 
and at apical junctions between Sertoli cells and spermatids. They are proposed 
to internalize intercellular junctions during the translocation of spermatocytes 
from basal to adluminal compartments of the seminiferous epithelium, and during 
sperm release from Sertoli cells. Although TBCs are specific to the seminiferous 
epithelium, they morphologically resemble podosomes in osteoclasts. Previously, 
we have reported that a key group of proteins consisting of N-WASp, Arp2/3, 
cortactin and dynamin that occur at podosomes also is present at TBCs. Here we 
explore the prediction that zyxin, a focal adhesion protein known to be present 
at podosomes, also is present at apical TBCs. A rabbit polyclonal anti-zyxin 
antibody (B71) was used to label fixed fragments and frozen sections of testis. 
In both fragments and sections, B71 labeled tubular regions of TBCs at apical 
sites of attachment between Sertoli cells and spermatids, in addition to being 
localized at actin related intercellular adhesion junctions termed ectoplasmic 
specializations. Although the function of zyxin at TBCs has yet to be 
determined, the protein is known to interact with the cytoplasmic domain of 
integrins at focal adhesions, and integrins are known to be present in TBCs.