Geminin deletion increases the number of fetal hematopoietic stem cells by affecting the expression of key transcription factors

Abstract

Balancing stem cell self-renewal and initiation of lineage specification programs is essential for the development and homeostasis of the hematopoietic system. We have specifically ablated geminin in the developing murine hematopoietic system and observed profound defects in the generation of mature blood cells, leading to embryonic lethality. Hematopoietic stem cells (HSCs) accumulated in the fetal liver following geminin ablation, while committed progenitors were reduced. Genome-wide transcriptome analysis identified key HSC transcription factors as being upregulated upon geminin deletion, revealing a gene network linked with geminin that controls fetal hematopoiesis. In order to obtain mechanistic insight into the ability of geminin to regulate transcription, we examined Hoxa9 as an example of a key gene in definitive hematopoiesis. We demonstrate that in human K562 cells geminin is associated with HOXA9 regulatory elements and its absence increases HOXA9 transcription similarly to that observed in vivo. Moreover, silencing geminin reduced recruitment of the PRC2 component SUZ12 to the HOXA9 locus and resulted in an increase in RNA polymerase II recruitment and H3K4 trimethylation (H3K4me3), whereas the repressive marks H3K9me3 and H3K27me3 were reduced. The chromatin landscape was also modified at the regulatory regions of HOXA10 and GATA1. K562 cells showed a reduced ability to differentiate to erythrocytes and megakaryocytes upon geminin silencing. Our data suggest that geminin is indispensable for fetal hematopoiesis and regulates the generation of a physiological pool of stem and progenitor cells in the fetal hematopoietic system.

GemC1 controls multiciliogenesis in the airway epithelium

“…We showed that Geminin antagonizes both GemC1 and McIdas, inhibiting their transactivation potential. Geminin has been shown to be expressed in proliferating cells and to regulate proliferation–differentiation decisions . Consistently, we observed the expression of Geminin in proliferating MTECs, which is decreased as cells progress toward differentiation, in parallel with the induction of GemC1, McIdas and FoxJ1.…”

GEMC 1 is a critical regulator of multiciliated cell differentiation

“…Increased Geminin expression has also been reported in many cancer cell types and the elevated expression of GEMC1 or Multicilin could provide an alternative means for facilitating DNA replication in this context (Kapoor, ). In addition, we have observed that the overexpression of Geminin that also has transcriptional roles, including the inhibition of Multicilin, inhibits GEMC1‐mediated activation of target genes (Fig D) (Yellajoshyula et al , ; Ma et al , ; Karamitros et al , ), suggesting the existence of reciprocal regulatory mechanisms between GEMC1 and Geminin.…”

GemC1 is a critical switch for neural stem cell generation in the postnatal brain

“…It was previously shown that GemC1 forms heterodimers with McIdas and Geminin, whereas Geminin acts antagonistically to GemC1 in the regulation of transcriptional activation of key transcription factors for multiciliogenesis (Arbi et al, 2016;Caillat et al, 2013;Caillat et al, 2015;Kyrousi et al, 2015;Patmanidi et al, 2017;Terré et al, 2016). As Geminin was previously shown to be implicated in stem cell self-renewal and differentiating decisions (Karamitros et al, 2015;Spella et al, 2011), antagonistic roles for Geminin and GemC1 in determining the ependymal cell lineage are likely. Although the human genetic findings we provide will require further validation by sequencing other congenital hydrocephalus patients, the fact that ependymogenesis in mice and humans shares many common characteristics (Coletti et al, 2018;Pressler & Auvin, 2013), suggests that the mechanism defined here in mice may be operative in some forms of human congenital hydrocephalus.…”