Table 2.

Actin Regulating Proteins in the Lens

Protein	Known functions	Epithelial Cell Localization (age, species)	Fiber Cell Localization (age, species)	Interactions With Lens Proteins	Lens Phenotype of Knockouts, Mutants or Inhibitor Treatment	References
Abi-2 (c-abl- interactor)	Adaptor that interacts with c- abl kinase to regulate WAVE- mediated Arp2/3 activation-driven actin assembly and dynamics	Cytoplasm and enriched at the apical epithelial- fiber cell junction, especially near lens equator (embryo, mouse)	Cytoplasm (embryo, mouse)	Co-localizes with WAVE-2, cadherins and β- catenin at apical interface between epithelial and fiber cells	Secondary fiber cell migration and orientation defects	(Grove et al., 2004; Maddala et al., 2011)
Cdc42	Filopodia formation	Cytoplasm (neonatal, mouse)	Cytoplasm, especially in the cortex at the basal and apical tips of fibers (neonatal, mouse)	-	Loss of actin filopodia between the lens placode and developing retina leads to abnormal optic cup and lens pit shape	(Chauhan et al., 2009; Chen et al., 2006; Chen et al., 2008)
p120-catenin	Binds cadherins to activate Rho GTPases to modulate actin dynamics	-	-	-	Mislocalization of myosin IIB away from apical surface of lens placode leading to placode invagination defect	(Lang et al., 2014)
Rac1	Actin stress fiber formation	Cytoplasm (neonatal, mouse)	Cytoplasm (neonatal, mouse)	-	Secondary fiber cell migration and orientation defects	(Chen et al., 2006; Chen et al., 2008; Maddala et al., 2011)
Rap1	Ras-like small GTPase needed for Cdc42 activation during cell-cell junction formation	-	-	-	Incomplete elongation of primary fibers with gap between anterior tips of primary fibers and apical surface of anterior epithelium, decreased actin filaments and disrupted E- cadherin and β- catenin staining	(Maddala et al., 2015)
RhoA/B/C	Promotes actin stress fiber formation	Cytoplasm (RhoA, neonatal, mouse)	Cytoplasm, especially in the cortex at the basal and apical tips of fibers (RhoA, neonatal, mouse)	-	Transgenic lens expression of C3 Rho GTPase inhibitor leads to small lenses with swollen fibers and decreased actin filaments, adherens junctions, gap junction and water channels	(Chen et al., 2006; Chen et al., 2008; Maddala et al., 2004; Rao et al., 2002)
RLIP76/RALBP 1	Effector of Ral1 and Rho/Rac	-	-	-	Transgenic lens expression leads to small lenses and microphthalmia with abnormal actin filament networks, Cdc42 inactivation and lower levels of phospho-cofilin	(Sahu et al., 2014)
Shroom3	Recruits actin filaments via Mena-family of actin modulators that are needed for apical constriction	-	-	Rock1/2	Reduced actin filaments and myosin IIB at apical surface of lens placode leading to abnormal placode invagination	(Plageman et al., 2010)
WAVE-2	Activates Arp2/3 leading to actin polymerization	Cytoplamic and enriched at the apical epithelial- fiber cell junction, especially near the lens equator (embryo, mouse)	Cytoplasmic (embryo, mouse)	-	-	(Maddala et al., 2011)