Abstract
ELMO1 (Engulfment and Cell Motility1) is a gene involved in regulating cell motility through the ELMO1-DOCK2-RAC complex. Contrary to DOCK2 (Dedicator of Cytokinesis 2) deficiency, which has been reported to be associated with immunodeficiency diseases, variants of ELMO1 have been associated with autoimmune diseases, such as diabetes and rheumatoid arthritis (RA). To explore the function of ELMO1 in immune cells and to verify the functions of novel ELMO1 variants in vivo, we established a zebrafish elmo1 mutant model. Live imaging revealed that, similar to mammals, the motility of neutrophils and T-cells was largely attenuated in zebrafish mutants. Consequently, the response of neutrophils to injury or bacterial infection was significantly reduced in the mutants. Furthermore, the reduced mobility of neutrophils could be rescued by the expression of constitutively activated Rac proteins, suggesting that zebrafish elmo1 mutant functions via a conserved mechanism. With this mutant, three novel human ELMO1 variants were transiently and specifically expressed in zebrafish neutrophils. Two variants, p.E90K (c.268G>A) and p.D194G (c.581A>G), could efficiently recover the motility defect of neutrophils in the elmo1 mutant; however, the p.R354X (c.1060C>T) variant failed to rescue the mutant. Based on those results, we identified that zebrafish elmo1 plays conserved roles in cell motility, similar to higher vertebrates. Using the transient-expression assay, zebrafish elmo1 mutants could serve as an effective model for human variant verification in vivo.
Highlights
The ELMO1 protein is known to interact with DOCK2 and participates in the regulation of cell motility by regulating the activity of the Rac proteins (Chang et al, 2020; Federici and Soddu, 2020)
We carried out Whole-mount in situ hybridization (WISH) to examine the expression pattern of elmo1 in zebrafish
From 22 h post fertilisation, elmo1 began to accumulate in the CNS, as was observed in a prior study (Epting et al, 2010) (Supplementary Figure S1A). Quantitative RT-PCR (qRT-PCR) revealed that elmo1 accumulated in leukocytes (Supplementary Figure S1B)
Summary
The ELMO1 protein is known to interact with DOCK2 and participates in the regulation of cell motility by regulating the activity of the Rac proteins (Chang et al, 2020; Federici and Soddu, 2020). DOCK2 deficiency has been reported to be associated with immunodeficiency diseases (Dobbs et al, 2015). Through the interaction with DOCK proteins or RhoG and subsequent activation of the small GTPase such as RACs, ELMO1 involves in regulating lymphocyte migration or promoting cancer cells invasion (Katoh et al, 2003; Jiang et al, 2011; Capala et al, 2014; Stevenson et al, 2014; Gong et al, 2018; Park et al, 2020). In Elmo1deficient mice, the number of neutrophils at chronic inflammation sites was significantly lower than that in wildtype mice This neutrophil chemotaxis defect leads to reduced inflammation and the relief of autoimmune diseases in mice (Arandjelovic et al, 2019). Elmo has been reported to regulate the vascular morphogenesis, the peripheral neuronal numbers and myelination, and the structure formation of kidney during zebrafish development (Epting et al, 2010; Epting et al, 2015; Sharma et al, 2016; Mikdache et al, 2020)
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