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2016 ; 59
(ä): 62-70
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Cell polarity proteins and spermatogenesis
#MMPMID27292315
Gao Y
; Xiao X
; Lui WY
; Lee WM
; Mruk D
; Cheng CY
Semin Cell Dev Biol
2016[Nov]; 59
(ä): 62-70
PMID27292315
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When the cross-section of a seminiferous tubule from an adult rat testes is
examined microscopically, Sertoli cells and germ cells in the seminiferous
epithelium are notably polarized cells. For instance, Sertoli cell nuclei are
found near the basement membrane. On the other hand, tight junction (TJ), basal
ectoplasmic specialization (basal ES, a testis-specific actin-rich anchoring
junction), gap junction (GJ) and desmosome that constitute the blood-testis
barrier (BTB) are also located near the basement membrane. The BTB, in turn,
divides the epithelium into the basal and the adluminal (apical) compartments.
Within the epithelium, undifferentiated spermatogonia and preleptotene
spermatocytes restrictively reside in the basal compartment whereas spermatocytes
and post-meiotic spermatids reside in the adluminal compartment. Furthermore, the
heads of elongating/elongated spermatids point toward the basement membrane with
their elongating tails toward the tubule lumen. However, the involvement of
polarity proteins in this unique cellular organization, in particular the
underlying molecular mechanism(s) by which polarity proteins confer cellular
polarity in the seminiferous epithelium is virtually unknown until recent years.
Herein, we discuss latest findings regarding the role of different polarity
protein complexes or modules and how these protein complexes are working in
concert to modulate Sertoli cell and spermatid polarity. These findings also
illustrate polarity proteins exert their effects through the actin-based
cytoskeleton mediated by actin binding and regulatory proteins, which in turn
modulate adhesion protein complexes at the cell-cell interface since TJ, basal ES
and GJ utilize F-actin for attachment. We also propose a hypothetical model which
illustrates the antagonistic effects of these polarity proteins. This in turn
provides a unique mechanism to modulate junction remodeling in the testis to
support germ cell transport across the epithelium in particular the BTB during
the epithelial cycle of spermatogenesis.
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