The pluripotency factor NANOG controls primitive hematopoiesis and directly regulates Tal1

Progenitors of the first hematopoietic cells in the mouse arise in the early embryo from Brachyury-positive multipotent cells in the posterior-proximal region of the epiblast, but the mechanisms that specify primitive blood cells are still largely unknown. Pluripotency factors maintain uncommitted cells of the blastocyst and embryonic stem cells in the pluripotent state. However, little is known about the role played by these factors during later development, despite being expressed in the postimplantation epiblast. Using a dual transgene system for controlled expression at postimplantation stages, we found that Nanog blocks primitive hematopoiesis in the gastrulating embryo, resulting in a loss of red blood cells and downregulation of erythropoietic genes. Accordingly, Nanog-deficient embryonic stem cells are prone to erythropoietic differentiation. Moreover, Nanog expression in adults prevents the maturation of erythroid cells. By analysis of previous data for NANOG binding during stem cell differentiation and CRISPR/Cas9 genome editing, we found that Tal1 is a direct NANOG target. Our results show that Nanog regulates primitive hematopoiesis by directly repressing critical erythroid lineage specifiers.This work was supported by the Spanish government (grant BFU2014-54608-P and BFU2017-84914-P to MM; grants RYC-2011-09209 and BFU-2012-35892 to JI). The Gottgens and Nichols laboratories are supported by core funding from the Wellcome Trust and MRC to the Wellcome and MRC Cambridge Stem Cell Institute. The CNIC is supported by the Spanish Ministry of Science, Innovation and Universities (MINECO) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505)S

Transient fibrosis resolves via fibroblast inactivation in the regenerating zebrafish heart

After myocardial infarction in the mammalian heart, millions of cardiomyocytes are lost and replaced by fibrotic scar tissue. While fibrosis is persistent in adult mammals, there are some vertebrates, including zebrafish, with the capacity for regeneration. This process does not occur in the absence of fibrosis. Here we studied subpopulations of collagen-producing cells and analyzed their fate after complete regeneration of the zebrafish myocardium. Our data show that fibroblasts persisted in the regenerated heart but shut down the profibrotic program. While fibrosis could be considered as detrimental to the regeneration process, our study reveals a positive effect on cardiomyocyte proliferation. Accordingly, a fibrotic response can be beneficial for heart regeneration. In the zebrafish (Danio rerio), regeneration and fibrosis after cardiac injury are not mutually exclusive responses. Upon cardiac cryoinjury, collagen and other extracellular matrix (ECM) proteins accumulate at the injury site. However, in contrast to the situation in mammals, fibrosis is transient in zebrafish and its regression is concomitant with regrowth of the myocardial wall. Little is known about the cells producing this fibrotic tissue or how it resolves. Using novel genetic tools to mark periostin b - and collagen 1alpha2 (col1a2)-expressing cells in combination with transcriptome analysis, we explored the sources of activated fibroblasts and traced their fate. We describe that during fibrosis regression, fibroblasts are not fully eliminated but become inactivated. Unexpectedly, limiting the fibrotic response by genetic ablation of col1a2 -expressing cells impaired cardiomyocyte proliferation. We conclude that ECM-producing cells are key players in the regenerative process and suggest that antifibrotic therapies might be less efficient than strategies targeting fibroblast inactivation

Nanog regulates Pou3f1 expression at the exit from pluripotency during gastrulation.

Pluripotency is regulated by a network of transcription factors that maintain early embryonic cells in an undifferentiated state while allowing them to proliferate. NANOG is a critical factor for maintaining pluripotency and its role in primordial germ cell differentiation has been well described. However, Nanog is expressed during gastrulation across all the posterior epiblast, and only later in development is its expression restricted to primordial germ cells. In this work, we unveiled a previously unknown mechanism by which Nanog specifically represses genes involved in anterior epiblast lineage. Analysis of transcriptional data from both embryonic stem cells and gastrulating mouse embryos revealed Pou3f1 expression to be negatively correlated with that of Nanog during the early stages of differentiation. We have functionally demonstrated Pou3f1 to be a direct target of NANOG by using a dual transgene system for the controlled expression of Nanog Use of Nanog null ES cells further demonstrated a role for Nanog in repressing a subset of anterior neural genes. Deletion of a NANOG binding site (BS) located nine kilobases downstream of the transcription start site of Pou3f1 revealed this BS to have a specific role in the regionalization of the expression of this gene in the embryo. Our results indicate an active role of Nanog inhibiting neural regulatory networks by repressing Pou3f1 at the onset of gastrulation.This article has an associated First Person interview with the joint first authors of the paper.This work was funded by the Spanish government [grant BFU2017-84914-P to M.M.]. The Gottgens laboratory is supported by core funding from the Wellcome Trust and Medical Research Council to the Wellcome and Medical Research Council Cambridge Stem Cell Institute. The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia, Innovación y Universidades (MCNU) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence [SEV-2015-0505]

Pluripotency factors regulate the onset of Hox cluster activation in the early embryo

Pluripotent cells are a transient population of the mammalian embryo dependent on transcription factors, such as OCT4 and NANOG, which maintain pluripotency while suppressing lineage specification. However, these factors are also expressed during early phases of differentiation, and their role in the transition from pluripotency to lineage specification is largely unknown. We found that pluripotency factors play a dual role in regulating key lineage specifiers, initially repressing their expression and later being required for their proper activation. We show that Oct4 is necessary for activation of HoxB genes during differentiation of embryonic stem cells and in the embryo. In addition, we show that the HoxB cluster is coordinately regulated by OCT4 binding sites located at the 3′ end of the cluster. Our results show that core pluripotency factors are not limited to maintaining the precommitted epiblast but are also necessary for the proper deployment of subsequent developmental programs.This work was funded by the Spanish government (grants BFU2017-84914-P and PID2020-115755GB-I00 to M.M.; BFU2016-74961-P and BFU2016-81887-REDT to J.L.G.-S.), the Andalusian government (grant BIO-396 to J.L.G.-S.), and the European Research Council (ERC; grant agreement 740041 to J.L.G.-S.). M.T. held Juan de la Cierva fellowships from the Spanish government (FJCI-2017-31791 and IJC2019-038897-I), R.R. and R.D.A. held FPU fellowships from the government, and J.V. was the recipient of a “La Caixa” fellowship. Work in the laboratory of J.L.G.-S. was supported by a María de Maetzu Unit of Excellence Grant (MDM-2016-0687) to the Department of Gene Regulation and Morphogenesis of the CABD. The CBMSO is supported by an institutional grant from the Fundación Ramon Areces, and the CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia e Innovación (MCIN), and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (grant CEX2020-001041-S funded by MICIN/AEI/10.13039/501100011033). : With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2020-001041-S)

Pluripotency factors regulate the onset of Hox cluster activation in the early embryo

Pluripotent cells are a transient population of the mammalian embryo dependent on transcription factors, such as OCT4 and NANOG, which maintain pluripotency while suppressing lineage specification. However, these factors are also expressed during early phases of differentiation, and their role in the transition from pluripotency to lineage specification is largely unknown. We found that pluripotency factors play a dual role in regulating key lineage specifiers, initially repressing their expression and later being required for their proper activation. We show that Oct4 is necessary for activation of HoxB genes during differentiation of embryonic stem cells and in the embryo. In addition, we show that the HoxB cluster is coordinately regulated by OCT4 binding sites located at the 3′ end of the cluster. Our results show that core pluripotency factors are not limited to maintaining the precommitted epiblast but are also necessary for the proper deployment of subsequent developmental programs

NANOG at the exit of pluripotency: new roles in the gastrulating mouse embryo

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 13-07-2018Esta tesis tiene embargado el acceso al texto completo hasta el 13-01-2020Developmental biology studies the processes by which a cell divides and differentiates to generate a full functional organism. Up to the onset of gastrulation, cells from the embryo remain pluripotent, but precisely at this stage they differentiate towards mesoderm, endoderm, ectoderm and primordial germ cells. Pluripotency factors maintain uncommitted cells of the blastocyst and embryonic stem cells in culture in the pluripotent state. However, little is known about the role played by these factors during later development, despite their being expressed in the postimplantation epiblast. At this stage, progenitors of the first hematopoietic cells in the mouse arise in the early mesodermal progenitors in the posterior-proximal region of the epiblast, but the mechanisms that specify primitive blood cells are still largely unknown. At the same time, the embryo polarizes and asymmetry arises with the formation of the anterior-posterior axis. Using a dual transgene system for controlled expression at postimplantation stages, we found that NANOG, a pluripotency factor crucial for pluripotency maintenance, blocks primitive hematopoiesis in the gastrulating embryo, resulting in a loss of red blood cells and downregulation of erythropoietic genes. Accordingly, Nanog deficient embryonic stem cells are prone to erythropoietic differentiation. Moreover, Nanog expression in adults prevents the maturation of erythroid cells. By analysis of available data for NANOG binding during stem cell differentiation and CRISPR/Cas9 genome editing, we found that Tal1 is a direct target of NANOG. We also found that Nanog represses anteriorization of the epiblast. By analyzing NanogKO ES cell RNAseq during naïve to primed transition and single cell RNAseq of gastrulating mouse embryos, we discovered that Nanog directly downregulates Pou3f1, that codes for a transcription factor important for anteriorization and neural development. Our results show that Nanog exerts crucial functions at the exit of pluripotency, and that it regulates primitive hematopoiesis and anteriorization of the embryo by directly repressing critical lineage specifiers

Nanog at the exit of pluripotency: new roles in the gastulating mouse embryo

Developmental biology studies the processes by which a cell divides and differentiates to generate a full functional organism. Up to the onset of gastrulation, cells from the embryo remain pluripotent, but precisely at this stage they differentiate towards mesoderm, endoderm, ectoderm and primordial germ cells. Pluripotency factors maintain uncommitted cells of the blastocyst and embryonic stem cells in culture in the pluripotent state. However, little is known about the role played by these factors during later development, despite their being expressed in the postimplantation epiblast. At this stage, progenitors of the first hematopoietic cells in the mouse arise in the early mesodermal progenitors in the posterior-proximal region of the epiblast, but the mechanisms that specify primitive blood cells are still largely unknown. At the same time, the embryo polarizes and asymmetry arises with the formation of the anterior-posterior axis. Using a dual transgene system for controlled expression at postimplantation stages, we found that NANOG, a pluripotency factor crucial for pluripotency maintenance, blocks primitive hematopoiesis in the gastrulating embryo, resulting in a loss of red blood cells and downregulation of erythropoietic genes. Accordingly, Nanog deficient embryonic stem cells are prone to erythropoietic differentiation. Moreover, Nanog expression in adults prevents the maturation of erythroid cells. By analysis of available data for NANOG binding during stem cell differentiation and CRISPR/Cas9 genome editing, we found that Tal1 is a direct target of NANOG. We also found that Nanog represses anteriorization of the epiblast. By analyzing NanogKO ES cell RNAseq during naïve to primed transition and single cell RNAseq of gastrulating mouse embryos, we discovered that Nanog directly downregulates Pou3f1, that codes for a transcription factor important for anteriorization and neural development. Our results show that Nanog exerts crucial functions at the exit of pluripotency, and that it regulates primitive hematopoiesis and anteriorization of the embryo by directly repressing critical lineage specifiers

Our First Choice: Cellular and Genetic Underpinnings of Trophectoderm Identity and Differentiation in the Mammalian Embryo.

The trophectoderm (TE) is the first cell population to appear in the mammalian preimplantation embryo, as the result of the differentiation of totipotent blastomeres located on the outer surface of the late morula. Trophectodermal cells arrange in a monolayer covering the expanding blastocyst and acquire an epithelial phenotype with distinct apicobasal polarity and a basal lamina placed toward the blastocyst interior. During later development through the periimplantation and gastrulation stages, the TE gives rise to extraembryonic membranes and cell types that will eventually form most of the fetal placenta, the specialized organ through which the embryo obtains maternal nourishment necessary for subsequent exponential growth. The specification of the TE is controlled by the combination of morphological cues arising from cell polarity with differential activity of signaling pathways such as Hippo and Notch, and the restriction to outer cells of lineage specifiers such as CDX2. This is possibly the first symmetry-breaking decision undertaken by the uncommitted cells produced by a handful of mitosis divisions from the newly fertilized zygote. Understanding how this cell lineage is specified will therefore provide unique information about development, differentiation, and how the interplay between cellular morphology and signaling and regulatory factors results in a correctly 3D-patterned embryo.Work in our lab is supported by the Spanish government (FPI-SO Fellowship to S.M., FPI Fellowship to J.G.S.A., and grant BFU2014-54608-P to M.M.). The CNIC is supported by the Ministry of Economy, Industry and Competitiveness (MEIC) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505).S

Transitions in cell potency during early mouse development are driven by Notch

The Notch signalling pathway plays fundamental roles in diverse developmental processes in metazoans, where it is important in driving cell fate and directing differentiation of various cell types. However, we still have limited knowledge about the role of Notch in early preimplantation stages of mammalian development, or how it interacts with other signalling pathways active at these stages such as Hippo. By using genetic and pharmacological tools in vivo, together with image analysis of single embryos and pluripotent cell culture, we have found that Notch is active from the 4-cell stage. Transcriptomic analysis in single morula identified novel Notch targets, such as early naïve pluripotency markers or transcriptional repressors such as TLE4. Our results reveal a previously undescribed role for Notch in driving transitions during the gradual loss of potency that takes place in the early mouse embryo prior to the first lineage decisions.This work was supported by the Spanish government (grants BFU2017-84914-P and BFU2015-72319-EXP to MM; FPI-SO Fellowship to SM); and grants NIH-R01DK084391, NIH-R01HD094868 and NIH-P30CA008748 to AKH. The CNIC is supported by the Spanish Ministry of Science, Innovation and Universities and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505).S

Nanog regulates Pou3f1 expression at the exit from pluripotency during gastrulation

Pluripotency is regulated by a network of transcription factors that maintain early embryonic cells in an undifferentiated state while allowing them to proliferate. NANOG is a critical factor for maintaining pluripotency and its role in primordial germ cell differentiation has been well described. However, Nanog is expressed during gastrulation across all the posterior epiblast, and only later in development is its expression restricted to primordial germ cells. In this work, we unveiled a previously unknown mechanism by which Nanog specifically represses genes involved in anterior epiblast lineage. Analysis of transcriptional data from both embryonic stem cells and gastrulating mouse embryos revealed Pou3f1 expression to be negatively correlated with that of Nanog during the early stages of differentiation. We have functionally demonstrated Pou3f1 to be a direct target of NANOG by using a dual transgene system for the controlled expression of Nanog Use of Nanog null ES cells further demonstrated a role for Nanog in repressing a subset of anterior neural genes. Deletion of a NANOG binding site (BS) located nine kilobases downstream of the transcription start site of Pou3f1 revealed this BS to have a specific role in the regionalization of the expression of this gene in the embryo. Our results indicate an active role of Nanog inhibiting neural regulatory networks by repressing Pou3f1 at the onset of gastrulation.This article has an associated First Person interview with the joint first authors of the paper.This work was funded by the Spanish government [grant BFU2017-84914-P to M.M.]. The Gottgens laboratory is supported by core funding from the Wellcome Trust and Medical Research Council to theWellcome and Medical Research Council Cambridge Stem Cell Institute. The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia, Innovación y Universidades MCNU) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence [SEV-2015-0505].S