Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 25, Pages 11411-11416Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1001823107
Keywords
actin dynamics; ectoplasmic specialization; seminiferous epithelial cycle; spermiogenesis
Categories
Funding
- National Institutes of Health, National Institute of Child Health and Human Development [R01 HD056034, U54 HD029990]
- Hong Kong Research Grants Council [HKU7693/07M]
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In epithelia, a primary damage of tight junctions (TJ) always leads to a secondary disruption of adherens junction (AJ), and vice versa. This response, if occurring in the testis, would disrupt spermatogenesis because the blood-testis barrier (BTB) must remain intact during the transit of spermatids in the seminiferous epithelium, which is associated with extensive apical ectoplasmic specialization (apical ES, a testis-specific AJ type) restructuring. As such, apical ES restructuring accompanied with the transit of developing spermatids during spermiogenesis must be segregated from the BTB to avoid an immunological barrier breakdown in all stages of the seminiferous epithelial cycle, except at stage VIII when spermiation and BTB restructuring take place concurrently. We report herein a mechanism involving restricted spatial and temporal expression of Arp2/3 complex and N-WASP, whose actin branching activity associated with apical ES and BTB restructuring in the seminiferous epithelium. High expression of Arp3 at the apical ES was shown to correlate with spermatid movement and proper spermatid orientation. Likewise, high Arp3 level at the BTB associated with its restructuring to accommodate the transit of preleptotene spermatocytes at stage VIII of the epithelial cycle. These findings were validated by in vitro and in vivo studies using wiskostatin, an inhibitor that blocks N-WASP from activating Arp2/3 complex to elicit actin branching. Inhibition of actin branching caused a failure of spermatid transit plus a loss of proper orientation in the epithelium, and a tightened Sertoli cell TJ permeability barrier, supporting the role of Arp2/3 complex in segregating the events of AJ and BTB restructuring.
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