Table 1.

Actin binding proteins (ABPs) that regulate Sertoli cell actin-based cytoskeleton at the BTB^*

Actin binding protein (ABP)	Mr in the testis (kDa)	Expression pattern in the seminiferous epithelium during the epithelial cycle	Function at the BTB	Phenotype(s) following KO in mice
Arp3	45	Expressed at the BTB in stage VII–IX tubules, highest at stage VIII) (Lie, et al. 2010a)	Induces branched actin polymerization	Arp3 KO mice died at blastocysts stage (Vauti, et al. 2007)
Eps8	97	Highly expressed at the BTB in stage V–VI (Lie, et al. 2009a)	Actin barded end capping and bundling	Eps8 KO mice were healthy and fertile (Scita, et al. 1999)
Espin	110	Expressed in the basal compartment, consistent with its localization at the BTB (Bartles, et al. 1996)	Actin bundling	Espin KO mice were viable and fertile (Revenu, et al. 2012)
Ezrin	85	Expressed in all stages at the BTB except stage IX (Gungor-Ordueri, et al. 2014b)	Actin bundling, constituent protein of intercellular bridges	Ezrin KO mice did not survive more than 1.5-wk after birth (Saotome, et al. 2004, Tamura, et al. 2005)
Drebrin E	110	Highly expressed at the BTB in stages IV–V and considerably diminished in stages VIII–XIV (Li, et al. 2011)	An adaptor protein with high affinity to Arp3 by recruiting Arp3 to the BTB	Not known
Fascin1	54	Expressed at the BTB in all stages but considerably diminished in stage VIII (Gungor-Ordueri, et al. 2014a)	Actin bundling	Fascin 1 KO mice were viable and fertile (Yamakita, et al. 2009)
Formin 1	180	Expressed at the BTB at stages I–VII, highly expressed at stage VI, diminished at stage VII, undetectable at stage VIII (Li, et al. 2015b)	Induces actin polymerization from the barbed (fast-growing) end	Formin 1 KO mice were viable and fertile (Zhou, et al. 2009)
Palladin	95	Highly expressed at stages I–V, diminished at stages VII–VIII (Qian, et al. 2013b)	Actin bundling	Palladin KO mice died around E15.5 day (Luo, et al. 2005)
Plastin 3	70	Expressed in all stages but considerably reduced at stage VIII (Li, et al. 2015c)	Actin bundling	Not known
Rai14	110	Expressed at the BTB in all stages but considerably diminished at stages VI–VII (Qian, et al. 2013a)	Actin binding, structurally associated with palladin	Not known
Vinculin	130	Expressed at the BTB (Mulholland, et al. 2001)	Adaptor protein, it has high affinity to α-actinin, an actin cross-linking protein	Vinculin KO mice could not survive beyond E10 day (Xu, et al. 1998)

^*This Table was not intended to be exhaustive, it summarized the functional properties of some actin binding proteins known to be involved in regulating Sertoli cell actin microfilaments or by recruiting proteins that can regulate actin microfilament dynamics. Abbreviations used: Arp3, actin-related protein 3; BTB, blood-testis barrier; Eps8, epidermal growth factor receptor pathway substrate 8; KO, knockout; Rai14, retinoic acid induced protein 14.