Genetically induced microtubule disruption in the mouse intestine impairs intracellular organization and transport

Abstract

In most differentiated cells, microtubules reorganize into noncentrosomal arrays that are cell-type specific. In the columnar absorptive enterocytes of the intestine, microtubules form polarized apical–basal arrays that have been proposed to play multiple roles. However, in vivo testing of these hypotheses has been hampered by a lack of genetic tools to specifically perturb microtubules. Here we analyze mice in which microtubules are disrupted by conditional inducible expression of the microtubule-severing protein spastin. Spastin overexpression resulted in multiple cellular defects, including aberrations in nuclear and organelle positioning and deficient nutrient transport. However, cell shape, adhesion, and polarity remained intact, and mutant mice continued to thrive. Notably, the phenotypes of microtubule disruption are similar to those induced by microtubule disorganization upon loss of CAMSAP3/Nezha. These data demonstrate that enterocyte microtubules have important roles in organelle organization but are not essential for growth under homeostatic conditions.

Mechanical Regulation of Stem Cell Proliferation and Fate Decisions by their Differentiated Daughters

“…Therefore, it will be important to determine what mediates the transcriptional response and whether it is directly responsible for the contractility or a feedback mechanism that amplifies it. Notably, we find that this cellular response to microtubule disruption is not universal, as microtubule disruption in differentiated cells of the intestinal epithelium did not result in a similar contractility phenotype 59 . Consistent with this, the upregulation of contractility-related genes was not noted upon microtubule disruption in cultured retinal pigment epithelium cells, suggesting distinct responses of different cell types to microtubule disruption 60 .…”

Mutated in colorectal cancer (MCC) : a novel centrosomal protein involved in intestinal homeostasis and disease

“…In this context, the misplacement of a number of organelles was also observed Wang et al, 2016). Additionally, conditional expression of Spastin, which encodes a MT-severing protein, in the mouse intestine resulted in misplacement of organelles (Muroyama et al, 2018). These studies indicate that MT filaments organization are essential for the establishment of intestinal cell shape and organelle distribution.…”

“…As previously described in the Introduction, γ-TuRC is essential for both MT nucleation at the centrosome and MT stabilization as it acts as a minus-end-capping protein complex (Anders and Sawin, 2011;Wiese and Zheng, 2000;Zheng et al, 1995). In differentiated intestinal cells, however, the major γ-TuRC-component γtubulin is redeployed to the apical nc-MTOC (Ameen et al, 2001;Muroyama et al, 2016Muroyama et al, , 2018Salas, 1999). Ameen et al (2001) showed that in the intestine of Ck8deficient mice, differentiated cells lacked CIFs and the localization of γ-tubulin was found to be dispersed within the cytoplasm of enterocytes, in contrast to its normal apical membrane localization.…”

“…It has been shown by two independent studies that the organization of the longitudinal apical-basal MT array is regulated by the calmodulinregulated spectrin-associated protein 3 (CAMSAP3), which tethers MT minus-end to the apical membrane (Noordstra et al, 2016;. In addition, another study has confirmed by inducible destruction of MT polymers in the mouse intestine through the expression of Spastin (microtubule-severing protein) that MT defects leads to several intracellular aberrations in organelle positioning and nutrient transport (Muroyama et al, 2018).…”

“…Additionally, Nedd1 (a γ-TuRC associated protein) is also described to be redeployed to the apical membrane of enterocytes (Muroyama et al, 2018). The relocalization of MT-nucleating γ-tubulin upon differentiation indicates that the MTOC activity is reassigned from the centrosome to the apical domain of intestinal cells where microtubule minus-ends are thenceforth anchored.…”