Tissue specific characterisation of Lim-kinase 1 expression during mouse embryogenesis

Abstract

The Lim-kinase (LIMK) proteins are important for the regulation of the actin cytoskeleton, in particular the control of actin nucleation and depolymerisation via regulation of cofilin, and hence may control a large number of processes during development, including cell tensegrity, migration, cell cycling, and axon guidance. LIMK1/LIMK2 knockouts disrupt spinal cord morphogenesis and synapse formation but other tissues and developmental processes that require LIMK are yet to be fully determined. To identify tissues and cell-types that may require LIMK, we characterised the pattern of LIMK1 protein during mouse embryogenesis. We showed that LIMK1 displays an expression pattern that is temporally dynamic and tissue-specific. In several tissues LIMK1 is detected in cell-types that also express Wilms' tumour protein 1 and that undergo transitions between epithelial and mesenchymal states, including the pleura, epicardium, kidney nephrons, and gonads. LIMK1 was also found in a subset of cells in the dorsal retina, and in mesenchymal cells surrounding the peripheral nerves. This detailed study of the spatial and temporal expression of LIMK1 shows that LIMK1 expression is more dynamic than previously reported, in particular at sites of tissue-tissue interactions guiding multiple developmental processes. KeywordsLimk; Kidney; Heart; Epithelia-to-mesenchyme transition; Mesenchyme-to-epithelia transition; Eye; Testes The regulation of the actin cytoskeleton is essential for a very large number of cellular process including cellular migration, axon guidance, cell cycling, and polarity acquisition and maintenance. LIMK1 and LIMK2 control one of the fundamental aspects of actin dynamics, the depolymerisation of filamentous actin, by phosphorylation of ADF/cofilin (Arber et al., 1998). LIMK1 is primarily phosphorylated by the family of small RhoGTPases. When phosophorylated, LIMK1 in turn phosphorylates cofilin and blocks its ability to sever and de-nucleate actin filaments. Phosphorylation also inhibits the actin debranching properties that are normally exerted by cofilin competing with the actin-branching Arp2/3 complex (Arber et al., 1998;Bernard, 2007;Bernstein and Bamburg, 2010 Recently it has been shown that LIMK1 can act downstream of BMP signalling, modulate synapse stability by binding to BMP type II receptors, and control cell cycling by shuttling to the nucleus (Bernstein and Bamburg, 2010;Davila et al., 2007;Eaton and Davis, 2005;Hocking et al., 2009;Wen et al., 2007). In vivo and in vitro experiments on LIMK1 knockout mice have shown that the loss of LIMK1 results in neuronal growth cone, dendritic spine, and actin defects that are associated with abnormal hippocampal long term potentiation and synaptic changes (Meng et al., 2002). LIMK1 knockout mice also display elevated fear response and weakened learning abilities (Meng et al., 2002). Interestingly, the role of LIMK1 in controlling dendritic spine morphology is at least in part modulated by inhibition of LIMK1 through post-transcriptional microRNA-medi...

A novel Rho-dependent pathway that drives interaction of fascin-1 with p-Lin-11/Isl-1/Mec-3 kinase (LIMK) 1/2 to promote fascin-1/actin binding and filopodia stability

“…Importantly, the mechanistic basis for the pathway downstream of Rho and Rho kinases resides in a previously unidentified process, the interaction of LIMK1/2 with fascin-1. Both of the LIMK isoforms are expressed in many tissues, although specificity of expression patterns and subcellular localizations has been described [ 37 , 45 , 46 ]. In this study, we identified the interaction of fascin-1 with active LIMK1/2 in SW480 cells by biochemical pull-down from cell extracts and by FRET/FLIM in intact, migrating cells.…”

Overview of the Muscle Cytoskeleton

“…LIMK1 and LIMK2 are most abundant in neural tissue, but are also present in numerous tissues including in the Z-discs of the developing heart (384, 501). LIMK1 phosphorylates cofilin-1 at serine 3, which inhibits cofilin-1’s function as an actin-severing protein (24).…”

The interactome of LIM domain proteins: The contributions of LIM domain proteins to heart failure and heart development

“…They regulate actin cytoskeletal assembly via the actin‐binding protein, cofilin, of which only the dephosphorylated form is active 70. LIMK1 itself is phosphorylated by Rho‐GTPases which in turn inactivate cofilin, thereby blocking its action on actin filaments and inhibiting de‐branching 71. This inhibition normally acts through the competitive binding of cofilin and the Arp2/3 complex to actin filaments.…”