NuMA-microtubule interactions are critical for spindle orientation and the morphogenesis of diverse epidermal structures.

Andrew Muroyama,Lindsey Seldin,Terry Lechler

doi:10.7554/elife.12504

Abstract

Mitotic spindle orientation is used to generate cell fate diversity and drive proper tissue morphogenesis. A complex of NuMA and dynein/dynactin is required for robust spindle orientation in a number of cell types. Previous research proposed that cortical dynein/dynactin was sufficient to generate forces on astral microtubules (MTs) to orient the spindle, with NuMA acting as a passive tether. In this study, we demonstrate that dynein/dynactin is insufficient for spindle orientation establishment in keratinocytes and that NuMA's MT-binding domain, which targets MT tips, is also required. Loss of NuMA-MT interactions in skin caused defects in spindle orientation and epidermal differentiation, leading to neonatal lethality. In addition, we show that NuMA-MT interactions are also required in adult mice for hair follicle morphogenesis and spindle orientation within the transit-amplifying cells of the matrix. Loss of spindle orientation in matrix cells results in defective differentiation of matrix-derived lineages. Our results reveal an additional and direct function of NuMA during mitotic spindle positioning, as well as a reiterative use of spindle orientation in the skin to build diverse structures.

Highlights

The development of complex tissues requires the coordination of cell fate decisions with the generation of correct tissue architecture
We examined the localization of NuMA fusion constructs lacking the nuclear localization sequence (NLS) alone, or in combination with the loss of the MT-binding domain (MTBD) or the entire NuMATIP domain (Figure 2C)
We found that p150glued of the dynactin complex co-localized with the cortical crescents of both NuMA and NuMADMTBD (Figure 3F,G)

Summary

Introduction

The development of complex tissues requires the coordination of cell fate decisions with the generation of correct tissue architecture. An LGN/NuMA/dynein-dynactin complex is a conserved regulator of spindle orientation in a number of cell types, including epidermal and neural progenitors in mammals, neuroblasts in Drosophila and zygotic divisions in Caenorhabditis elegans. Targeting dynein/dynactin to the cell cortex was sufficient to induce spindle movements, consistent with it playing a direct role in force generation (Kotak et al, 2012). These data have led to the proposition that LGN and NuMA form a passive tether, which

Methods

Results

Conclusion