Essential requirement of mammalianPumiliofamily in embryonic development

Abstract

Mouse PUMILIO1 (PUM1) and PUMILIO2 (PUM2) belong to the PUF (Pumilio/FBF) family, a highly conserved RNA binding protein family whose homologues play critical roles in embryonic development and germ line stem cell maintenance in invertebrates. However, their roles in mammalian embryonic development and stem cell maintenance remained largely uncharacterized. Here we report an essential requirement of the Pum gene family in early embryonic development. A loss of both Pum1 and Pum2 genes led to gastrulation failure, resulting in embryo lethality at E8.5. Pum-deficient blastocysts, however, appeared morphologically normal, from which embryonic stem cells (ESCs) could be established. Both mutant ESCs and embryos exhibited reduced growth and increased expression of endoderm markers Gata6 and Lama1, making defects in growth and differentiation the likely causes of gastrulation failure. Furthermore, ESC Gata6 transcripts could be pulled down via PUM1 immunoprecipitation and mutation of conserved PUM-binding element on 3′UTR (untranslated region) of Gata6 enhanced the expression of luciferase reporter, implicating PUM-mediated posttranscriptional regulation of Gata6 expression in stem cell development and cell lineage determination. Hence, like its invertebrate homologues, mouse PUM proteins are conserved posttranscriptional regulators essential for embryonic and stem cell development.

Mammalian Pum1 and Pum2 Control Body Size via Translational Regulation of the Cell Cycle Inhibitor Cdkn1b

“…Pum1 −/− and Pum2 −/− mice were smaller throughout postnatal development, with a largely proportional size reduction among organs. A gene dosage effect of Pum alleles on body weight has been previously suggested ( Gennarino et al, 2015 ; Siemen et al, 2011 ), consistent with the overall dosage-sensitive behavior of PUM proteins ( Gennarino et al, 2018 ; Lee et al, 2016 ; Lin et al, 2018b ). In this study, we demonstrated a clear effect of gene dosage for Pum1 and, more interestingly, a synergistic effect of Pum1 and Pum2 on body and organ size.…”

“…Given similar roles of Pum1 and Pum2 in cell proliferation, we therefore propose that Pum1 and Pum2 play a coordinated role in the control of body size. To test this hypothesis, we generated mouse mutants with different combinations of Pum1 - and Pum2 -null mutant alleles, with the exception of Pum1 −/− and Pum2 −/− double homozygotes, which failed during early embryonic development ( Lin et al, 2018b ). We noted a remarkable dosage effect of Pum genes on body weight ( Figures 7A and 7B ).…”

“…In multiple species, homologs of Pumilio are required for germline development and differentiation, in particular germline stem cell maintenance ( Cao et al, 2010 ; Crittenden et al, 2002 ; Forbes and Lehmann, 1998 ; Lin and Spradling, 1997 ; Parisi and Lin, 2000 ; Wickens et al, 2002 ). The function of the two mammalian members of the PUF family, Pumilio RNA-binding family members 1 and 2 (PUM1 and PUM2), has been investigated in genetic studies in the mouse ( Chen et al, 2012 ; Gennarino et al, 2015 ; Lin et al, 2018b ; Mak et al, 2016 ; Xu et al, 2007 ; Zhang et al, 2017 ). Pum -mutant mice have reduced body weight, suggesting that PUF proteins may function outside the gonads and may be required for growth in mammals ( Chen et al, 2012 ; Siemen et al, 2011 ).…”

Pumilio proteins utilize distinct regulatory mechanisms to achieve complementary functions required for pluripotency and embryogenesis

“…Pum1 has also been implicated in human neurodegeneration and motor ataxia (28,29) and in the maintenance of genomic stability in mice (30). Recent work showed that decreasing the number of Pum1 + and/ or Pum2 + alleles reduces body size in a dose-dependent manner, partly due to translational derepression of the cell-cycle inhibitor CDKN1B (26) and that complete deficiency of Pum1 and Pum2 leads to embryonic lethality (31). Conditional knockout of Pum1 and Pum2 in the nervous system affects neural stem-cell maintenance by derepressing the translation of many mRNAs (32,33).…”

Pumilio Proteins Exert Distinct Biological Functions and Multiple Modes of Post-Transcriptional Regulation in Embryonic Stem Cell Pluripotency and Early Embryogenesis

“…Similarly, little is known about the function of Pum1; conditional knockout of Pum1 in the mouse testis results in decreased fertility (25). Recently, Pum1-Pum2 double mutant been shown to be embryonic lethal (26) and that Pum1 and Pum2 deficiencies reduces body size in a dose-dependent manner, partly due to translational de-repression of the cell cycle inhibitor CDKN1B (24).…”