Oddly enough, some cells in the thalamus of cKO embryos also shown upregulated expression from the cell routine inhibitor p21 (Figure 2figure dietary supplement 2b,c). Taken?together, the info shows that mitotic spindle flaws in cKO progenitors aren’t catastrophic by itself, but efficiently cause cell routine arrest and apoptotic cell loss of life upon conclusion of mitosis. Co-deletion of in cKO embryos rescues apoptosis however, not forebrain development Since substantial apoptosis in cKO brains was correlated with AZD-4320 p53 induction, we wondered whether cell loss of life was p53-reliant and the reason for aborted human brain development. with Amount 7d, e, f. elife-67989-fig7-data1.xlsx (24K) GUID:?F950B365-A454-4989-A683-41A893F2ABFB Transparent reporting form. elife-67989-transrepform.pdf (246K) GUID:?177FB7BF-9374-42F9-B8C1-47C4B88B3CAD Data Availability StatementAll data generated or analyzed during this study are included in the manuscript and supporting files. Abstract Microtubules that assemble the mitotic spindle are generated by centrosomal nucleation, chromatin-mediated nucleation, and nucleation from the surface of other microtubules mediated by the augmin complex. Impairment of centrosomal nucleation in apical progenitors of the developing mouse brain induces p53-dependent apoptosis and causes non-lethal microcephaly. Whether disruption of non-centrosomal nucleation has similar effects is usually unclear. Here, we show, using mouse embryos, that conditional knockout of the augmin subunit in apical progenitors led to spindle defects and mitotic delay. This triggered massive apoptosis and abortion of brain development. Co-deletion of rescued cell death, but surviving progenitors failed to organize a pseudostratified epithelium, and brain development still failed. This could be explained by exacerbated mitotic errors and producing chromosomal defects including increased DNA damage. Thus, in contrast to centrosomes, augmin is crucial for apical progenitor mitosis, and, even in the absence of p53, for progression of brain development. egg extract and cultured cell models have generated a wealth of information regarding the types of AZD-4320 spindle defects that occur when specific nucleation pathways are compromised, how these defects impinge on cell fate and development remains poorly defined. Gene mutations that cause functional or numerical centrosome aberrations are associated with main microcephaly, a developmental disorder that results in the?reduced thickness of the cerebral cortex. Depletion of apical progenitors following abnormal mitoses has been identified as a pathogenic mechanism (Jayaraman et al., 2018; Marthiens and Basto, 2020; Nano and Basto, 2017). Apical progenitors of the developing cerebral cortex are highly polarized cells. Their cell body are positioned in the ventricular NAV3 zone (VZ), while their apical and basal processes contact the ventricular surface (VS)?and basal lamina, respectively (Arai and Taverna, 2017; Chenn et al., 1998; Chou et al., 2018). Prior to mitosis, the nucleus migrates apically and mitotic chromosome segregation occurs near AZD-4320 the apical surface. Early during cortical development, apical progenitors divide symmetrically, expanding the progenitor pool. At later stages they switch to self-renewing asymmetric mitoses, producing a neuron or intermediate progenitor in each division. Centrosomal microtubules were proposed to be at the core of these fate decisions, by controlling the distribution of cell fate determinants through correct positioning of the mitotic spindle (Homem et al., 2015; Taverna et al., 2014; Uzquiano et al., 2018). Recent work showed that progenitor fate is usually strongly impacted by mitotic duration. Mitotic delay results in more neurogenic divisions and an increased percentage of progenitors undergoing p53-dependent apoptosis, depleting the progenitor pool (Mitchell-Dick et al., 2020; Pilaz et al., 2016). Consistently, mitotic delay, premature differentiation, and apoptosis have all been observed for centrosome defects in mouse models of main microcephaly (Insolera et al., 2014; Lin et al., 2020; Marjanovi? et al., 2015; McIntyre et al., 2012; Novorol et al., 2013). Interestingly, in cases where it has been tested, such as (Watanabe et al., 2016). However, since early mouse development occurs in the absence of centrosomes (Gueth-Hallonet et al., 1993), the embryos in the above studies lacked two of the three mitotic nucleation pathways. Early functional studies by augmin knockdown in cell lines explained mitotic defects that ranged from relatively moderate for cells (Goshima et al., 2008; Meireles et al., 2009) to more severe for human cells (Lawo et al., 2009), suggesting cell type- or organism-specific differences. Consistent with this, the knockout of augmin in has no obvious phenotype (Edzuka et al., 2014), augmin.