Abstract
Heterozygous loss of human PAFAH1B1 (coding for LIS1) results in the disruption of neurogenesis and neuronal migration via dysregulation of microtubule (MT) stability and dynein motor function/localization that alters mitotic spindle orientation, chromosomal segregation, and nuclear migration. Recently, human- induced pluripotent stem cell (iPSC) models revealed an important role for LIS1 in controlling the length of terminal cell divisions of outer radial glial (oRG) progenitors, suggesting cellular functions of LIS1 in regulating neural progenitor cell (NPC) daughter cell separation. Here, we examined the late mitotic stages NPCs in vivo and mouse embryonic fibroblasts (MEFs) in vitro from Pafah1b1-deficient mutants. Pafah1b1-deficient neocortical NPCs and MEFs similarly exhibited cleavage plane displacement with mislocalization of furrow-associated markers, associated with actomyosin dysfunction and cell membrane hyper-contractility. Thus, it suggests LIS1 acts as a key molecular link connecting MTs/dynein and actomyosin, ensuring that cell membrane contractility is tightly controlled to execute proper daughter cell separation.
Highlights
(smooth brain) is a brain malformation disorder associated with haploinsufficiency of Lissencephaly-1 (LIS1), called PAFAH1B1 (Platelet-activating factor acetylhydrolase IB subunit alpha) (Dobyns et al, 1993; Hattori et al, 1994; Reiner et al, 1993; Moon and Wynshaw-Boris, 2013)
To elucidate molecular mechanisms underlying LIS1-dependent neural progenitor cell (NPC) regulation during neocortical development, mitotic phenotypes of Pafah1b1-deficient NPCs were analyzed by conducting genetic and immunohistochemical approaches on mouse neocortices derived at embryonic day 14.5 (E14.5) (Figure 1A–E)
To deplete Pafah1b1 sparsely in neocortical NPCs during early embryonic development, we first generated MADM-11TG/TG,Pafah1b1 (TG: tdTomato-GFP fusion) mice coexpressing the heterozygous Pafah1b1 knock-out (KO) allele. These mice were mated with MADM11GT/GT;Emx1Cre/+ (GT: GFP-tdTomato fusion) to generate the experimental mosaic animals which carry sparsely labeled NPCs with different expression levels of LIS1 (MADM-11GT/TG,Pafah1b1;Emx1Cre/+, abbreviated as Pafah1b1-MADM) (Figure 1B)
Summary
(smooth brain) is a brain malformation disorder associated with haploinsufficiency of Lissencephaly-1 (LIS1), called PAFAH1B1 (Platelet-activating factor acetylhydrolase IB subunit alpha) (Dobyns et al, 1993; Hattori et al, 1994; Reiner et al, 1993; Moon and Wynshaw-Boris, 2013). The mitotic phenotypes of Pafah1b1 mutants are closely related and consistent with those of other mutants of MT/dynein-associated proteins such as LGN, NDE1, and NDEL1 (Bradshaw and Hayashi, 2017; Doobin et al, 2016; Wynne and Vallee, 2018). Unlike these other mouse mutants of LIS1-interacting proteins, Pafah1b1 mutants displayed a significant decrease in neuroepithelial stem cells in the neocortex and subsequent neonatal death compared with a less catastrophic phenotype seen in radial glial (RG) progenitors (Yingling et al, 2008).
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