Trp-Asp (WD) Repeat Domain 1 Is Essential for Mouse Peri-implantation Development and Regulates Cofilin Phosphorylation

Abstract

Edited by Xiao-Fan WangTrp-Asp (WD) repeat domain 1 (WDR1) is a highly conserved actin-binding protein across all eukaryotes and is involved in numerous actin-based processes by accelerating Cofilin severing actin filament. However, the function and the mechanism of WDR1 in mammalian early development are still largely unclear. We now report that WDR1 is essential for mouse periimplantation development and regulates Cofilin phosphorylation in mouse cells. The disruption of maternal WDR1 does not obviously affect ovulation and female fertility. However, depletion of zygotic WDR1 results in embryonic lethality at the periimplantation stage. In WDR1 knock-out cells, we found that WDR1 regulates Cofilin phosphorylation. Interestingly, WDR1 is overdosed to regulate Cofilin phosphorylation in mouse cells. Furthermore, we showed that WDR1 interacts with Lim domain kinase 1 (LIMK1), a well known phosphorylation kinase of Cofilin. Altogether, our results provide new insights into the role and mechanism of WDR1 in physiological conditions.The actin cytoskeleton is a highly dynamic structure that regulates cell motility, adhesion, division, and growth and has a fundamental function in embryonic development (1-3). In physiological conditions, actin filaments are continually assembled and disassembled in response to varied cellular activities (4, 5). The dynamics of F-actin is well orchestrated by a large number of actin-binding proteins (5, 6). Actin-depolymerizing factor Cofilin plays critical roles in the modulation of actin cytoskeleton dynamics (7). In vitro, Cofilin severs actin filament at low concentrations, whereas it fully decorates actin filaments and suppresses the severing activity at high concentrations (8, 9). In addition, Cofilin severing F-actin is not explained well for how the filaments of actin cytoskeleton can be rapidly disassembled in physiological conditions (4). Thus, the function of Cofilin in actin dynamics depends not only on its relative concentration to actin, but also on other regulatory proteins in vivo. Dysfunction of these regulating proteins results in aberrant actin cytoskeleton in various cellular and developmental processes (10 -12).Cofilin directly binds with actin to function as a regulator of the actin dynamics (13). However, the phosphorylation of Cofilin at Ser-3 blocks its binding site to actin (14, 15). Thus, the activity of Cofilin is controlled by phosphorylation and dephosphorylation processes, which are regulated by cascade reactions of several protein kinases and phosphatases. Lim domain kinases (LIMKs) 4 and testis-specific protein kinases (TESKs) are responsible for the phosphorylation of Cofilin, whereas slingshot (SSH) family protein phosphatases and pyridoxal phosphatase (PDXP) catalyze the dephosphorylation reaction (16 -20). These kinases and phosphatases are also regulated by their phosphorylation or localization in cytoplasm to maintain the level of Cofilin phosphorylation in response to extracellular stimuli (21-23).The activity of Cofilin on actin disassembly is gr...

Coronin 1A depletion restores the nuclear stability and viability of Aip1/Wdr1-deficient neutrophils

“…This overall dephosphorylation of cofilin was also found in Wdr1 knockout mouse cells (Xiao et al, 2017) and in the neutrophils of an LLS patient harboring a D26N mutation in Wdr1 (Kuhns et al, 2016). Xiao et al (2017) were able to explain this effect of Wdr1 deficiency by showing that mouse WDR1 binds to the LIM-kinase (LIMK1) microtubule binding domain, thus preventing its inhibitory localization to microtubules and enhancing its ability to phosphorylate cofilin. Interestingly, even though the two point mutations shown to cause cofilin unphosphorylation, our carmin W540R and the human D26N.…”

AIP1 and Cofilin control the actin dynamics to modulate the asymmetric division and cytokinesis in mouse oocytes

“…We found that phosphorylated Cofilin was distributed at the periphery of the spindle in mouse oocytes, which is consistent with previous studies. 23,50 Previous studies suggested that the interaction of AIP1 with LIMKs PDZ region might regulate Cofilin phosphorylation via LIMKs by inhibiting its binding to the microtubules in mouse embryonic fibroblast cells. 23 They suggest that mouse AIP1 binds to LIMKs and enhances its activity to phosphorylate ADF/Cofilin, which could result in stabilization, rather than disassembly, of actin filaments.…”

“…29 Furthermore, AIP1 is essential for mouse peri-implantation development. 23 AIP1 was identified as a major cofactor that collaborates with ADF/Cofilin-decorated actin filaments and enhances filament disassembly. 6 It binds to the Cofilin-F-actin complex and strongly enhances the severing activity of Cofilin on actin filaments by capping the barbed ends of the severed filaments, resulting in acceleration of actin depolymerization.…”

Functions of actin-interacting protein 1 (AIP1)/WD repeat protein 1 (WDR1) in actin filament dynamics and cytoskeletal regulation

“…Genetic studies show that AIP1 deficiency causes lethality in mice [81,82], insects [17], nematodes [20], and plants [83]. In addition, recessive point mutations in the human WDR1 gene cause severe blood disorders [84,85].…”

“…Although most of genetic observations are consistent with the function of AIP1 to disassemble ADF/cofilin-bound actin filaments, whether AIP1 has other ADF/cofilin-independent functions remains unknown. A recent study shows that mouse WDR1 binds to LIM-kinase and enhances its activity to phosphorylate ADF/cofilin [82], which could result in stabilization, rather than disassembly, of actin filaments. Therefore, consequences of AIP1/WDR1 up-regulation in cancer and other conditions need to be carefully evaluated in each case.…”