The Heterotaxy Gene CCDC11 is Essential for Cytokinesis and Cell-Cell Adhesion via RhoA Regulation

Abstract

RhoA is critical for cytokinesis and cell-cell adhesion. While we have made significant progress in identifying the regulators of RhoA, our understanding remains incomplete. In multiple patients with heterotaxy (Htx), a disorder of left-right (LR) patterning of the internal organs, mutations in CCDC11 were identified. In Xenopus, depletion of ccdc11 causes defects in LR patterning, recapitulating the patients' phenotype. Interestingly, with ccdc11 depletion, normally monociliated cells of the Left-Right Organizer (LRO) exhibited multiple cilia per cell.While investigating this multiciliated phenotype, we unexpectedly discovered that ccdc11 is critical for cytokinesis. In addition, CCDC11 depletion alters cell-cell adhesion with loss of junctional adhesion molecules.Based on these phenotypes, reminiscent of RhoA loss of function, we demonstrate that CCDC11 colocalizes with RhoA during cytokinesis and regulates total RhoA protein levels. In conclusion, CCDC11 surprisingly connects cytokinesis and LR patterning via RhoA regulation, providing a potential mechanism for disease pathogenesis. RESULTS AND DISCUSSION Ccdc11 is important in establishing left-right asymmetryThe embryo breaks bilateral symmetry beginning at the Left-Right Organizer (LRO) [1][2][3]. Here, a subset of cells with motile monocilia drive extracellular fluid towards the left, which is sensed by immotile monocilia [4][5][6].As a consequence, dand5 (Cerl2 in mouse, coco in frog), which is initially expressed bilaterally at the margin of the LRO, is repressed on the left [2,7,8]. Repression of dand5 leads to expression of pitx2 in the left lateral plate mesoderm [1,9,10]. Pitx2 drives asymmetric organogenesis such that the heart, which initiates as a midline tube, loops to the right while other organs like the gut also undergo asymmetric morphogenesis [11].Therefore, a signaling cascade including cilia driven extracellular fluid flow, dand5, and pitx2 establish laterality of internal organs such as the heart.CCDC11 plays a key role in establishing LR asymmetry [12][13][14][15]. A number of Htx patients have CCDC11 alleles, and depletion of ccdc11 causes LR patterning defects in zebrafish and Xenopus [12][13][14][15]. Consistent with these studies, we also show that ccdc11 is important for LR patterning in Xenopus. We depleted Ccdc11 using F0 CRISPR and examined cardiac looping ( Figure 1A). We found that embryos depleted of ccdc11 showed significant cardiac looping defects (~22%) compared to uninjected controls. In addition, overexpression of human CCDC11 also showed significant cardiac looping defects (~15%) compared to uninjected controls suggesting that precise regulation of CCDC11 levels is necessary for its proper function ( Figure 1A). To place CCDC11 in the LR patterning cascade, we next examined pitx2 and coco. Using a ccdc11 morpholino oligo (MO), we found that ccdc11 knockdown led to abnormal patterns of both pitx2 (~25%) and coco (~80%) (Figures 1B-C). Therefore, using either depletion strategy, F0 CRISPR or MO, ccdc11 depletion is critica...

Mechanical stretch scales centriole number to apical area via Piezo1 in multiciliated cells

“…Third, we induced cytokinesis defects by knocking down ccdc11 using a morpholino oligo (MO) in X. tropicalis ( Kulkarni et al, 2018b ). MCCs are mitotically mature; however, if their progenitor fails to undergo cytokinesis, then the resultant MCC can be much larger ( Figure 1—figure supplement 2a ).…”

Xenopus to the rescue: A model to validate and characterize candidate ciliopathy genes

“…(5) Xenopus allows us to carry out a rapid loss of function (LOF) and gain of function (GOF) analysis in the context of disease phenotypes (Bhattacharya, Marfo, Li, Lane, & Khokha, 2015;Boon et al, 2014;Boskovski et al, 2013;Griffin et al, 2018;S. Kulkarni, Stephenson, et al, 2018;Kulkarni, Griffin, Date, Liem Jr., & Khokha, 2018;Toriyama et al, 2016;Wallmeier et al, 2014).…”

“…(4) The fate maps of early cleavage stage embryos allow us to inject specific blastomeres to KO genes in specific tissues with relatively good accuracy to bypass the early embryonic lethality. (5) Xenopus allows us to carry out a rapid loss of function (LOF) and gain of function (GOF) analysis in the context of disease phenotypes (Bhattacharya, Marfo, Li, Lane, & Khokha, 2015; Boon et al, 2014; Boskovski et al, 2013; Griffin et al, 2018; S. Kulkarni, Stephenson, et al, 2018; Kulkarni, Griffin, Date, Liem Jr., & Khokha, 2018; Kulkarni & Khokha, 2018; Toriyama et al, 2016; Wallmeier et al, 2014). Specifically, many hundreds of synchronized embryos can be microinjected at cleavage stages in an hour to either overexpress, deplete, or label proteins with fluorescent reporter tags.…”