Cross-Talk between Tight and Anchoring Junctions—Lesson from the Testis

Abstract

Spermatogenesis takes place in the seminiferous tubules in adult testes such as rats, in which developing germ cells must traverse the seminiferous epithelium while spermatogonia (2n, diploid) undergo mitotic and meiotic divisions, and differentiate into elongated spermatids (1n, haploid). It is conceivable that this event involves extensive junction restructuring particularly at the blood-testis barrier (BTB, a structure that segregates the seminiferous epithelium into the basal and the adluminal compartments) that occurs at stages VII-VIII of the seminiferous epithelial cycle. As such, cross-talk between tight (TJ) and anchoring junctions [e.g., basal ectoplasmic specialization (basal ES), adherens junction (AJ), desmosome-like junction (DJ)] at the BTB must occur to coordinate the transient opening of the BTB to facilitate preleptotene spermatocyte migration. Interestingly, while there are extensively restructuring at the BTB during the epithelial cycle, the immunological barrier function of the BTB must be maintained without disruption even transiently. Recent studies using the androgen suppression and Adjudin models have shown that anchoring junction restructuring that leads to germ cell loss from the seminiferous epithelium also promotes the production of AJ (e.g., basal ES) proteins (such as N-cadherins, catenins) at the BTB site. We postulate the testis is using a similar mechanism during spermatogenesis at stage VIII of the epithelial cycle that these induced basal ES proteins, likely form a "patch" surrounding the BTB, transiently maintain the BTB integrity while TJ is "opened", such as induced by TGF-b3 or TNFa, to facilitate preleptotene spermatocyte migration. However, in other stages of the epithelial cycle other than VII and VIII when the BTB remains "closed" (for ~10 days), anchoring junctions (e.g., AJ, DJ, and apical ES) restructuring continues to facilitate germ cell movement. Interestingly, the mechanism(s) that governs this communication between TJ and anchoring junction (e.g., basal ES and AJ) in the testis has remained obscure until recently. Herein, we provide a critical review based on the recently available data regarding the cross-talk between TJ and anchoring junction to allow simultaneous maintenance of the BTB and germ cell movement across the seminiferous epithelium.

Blood–testis barrier and Sertoli cell function: lessons from SCCx43KO mice

“…At the BTB level, the possibility that gap junctions exert such a control on the other components of the barrier has been postulated (Yan et al 2008, Lee et al 2009, Figure 1 Seminiferous epithelium of adult WT mice and BTB composition. (A) Toluidine blue stained semi-thin section of an adult WT testis.…”

“…testosterone, transcription factors, FSH and/or GC (Mruk & Cheng 2004, Yan et al 2008, Lie et al 2009, Morrow et al 2010. Interestingly, postmeiotic GC have been shown to have an inhibitory effect on CLAUDIN11 expression in rat seminiferous epithelium, whereas spermatogonia and premeiotic spermatocytes have no effect (Florin et al 2005).…”

Endogenous EGF maintains Sertoli germ cell anchoring junction integrity and is required for early recovery from acute testicular ischemia/reperfusion injury

“…These results also lend support to the above-mentioned notion that functional integrity of AJs is indispensable for early recovery from testicular IR injury. Essentially, the dynamic nature of spermatogenesis requires AJs to act rapidly to extracellular stimuli in order to permit a timely passage of developing germ cells across the seminiferous epithelium from the basal to the adluminal compartment (Yan et al 2008). Therefore, the half-life of AJs component proteins is usually short and thereby Sertoli germ cell contacts are subject to extensive alteration and remodeling (Cheng et al 2011).…”

Reinke´s Crystals in Perivascular and Peritubular Leydig Cells

“…Perivascular cells, in addition, thus control the hypothalamus-hypophysis-testis axis and activity of the two testis compartments. [1][2][3] Both perivascular and peritubular Leydig cells have Reinke´s crystals. Some investigators speculate that this crystal is a by-product of steroidogenesis and the production of testosterone.…”

“…[1][2][3] The vast majority of the male sex gonad is occupied by tortuous structures called seminiferous tubules, in which spermatogenesis and production of spermatozoa occur. The interstitial compartment consists of a loose connective tissue rich in blood vessels.…”