Loss of function of mouse Pax-Interacting Protein 1-associated glutamate rich protein 1a (Pagr1a) leads to reduced Bmp2 expression and defects in chorion and amnion development

Understanding copy number variations through their genes: a molecular view on 16p11.2 deletion and duplication syndromes

Neurodevelopmental disorders (NDDs) include a broad spectrum of pathological conditions that affect >4% of children worldwide, share common features and present a variegated genetic origin. They include clinically defined diseases, such as autism spectrum disorders (ASD), attention-deficit/hyperactivity disorder (ADHD), motor disorders such as Tics and Tourette's syndromes, but also much more heterogeneous conditions like intellectual disability (ID) and epilepsy. Schizophrenia (SCZ) has also recently been proposed to belong to NDDs. Relatively common causes of NDDs are copy number variations (CNVs), characterised by the gain or the loss of a portion of a chromosome. In this review, we focus on deletions and duplications at the 16p11.2 chromosomal region, associated with NDDs, ID, ASD but also epilepsy and SCZ. Some of the core phenotypes presented by human carriers could be recapitulated in animal and cellular models, which also highlighted prominent neurophysiological and signalling alterations underpinning 16p11.2 CNVs-associated phenotypes. In this review, we also provide an overview of the genes within the 16p11.2 locus, including those with partially known or unknown function as well as non-coding RNAs. A particularly interesting interplay was observed between MVP and MAPK3 in modulating some of the pathological phenotypes associated with the 16p11.2 deletion. Elucidating their role in intracellular signalling and their functional links will be a key step to devise novel therapeutic strategies for 16p11.2 CNVs-related syndromes.

Aberrant lipid accumulation in the mouse visceral yolk sac resulting from maternal diabetes and obesity

Maternal diabetes and obesity in pregnancy are well-known risk factors for structural birth defects, including neural tube defects and congenital heart defects. Progeny from affected pregnancies are also predisposed to developing cardiometabolic disease in later life. Based upon in vitro embryo cultures of rat embryos, it was postulated that nutrient uptake by the yolk sac is deficient in diabetic pregnancies. In contrast, using two independent mouse models of maternal diabetes, and a high-fat diet-feeding model of maternal obesity, we observed excessive lipid accumulation at 8.5 days in the yolk sac. The numbers as well as sizes of intracellular lipid droplets were increased in yolk sacs of embryos from diabetic and obese pregnancies. Maternal metabolic disease did not affect expression of lipid transporter proteins, including ApoA1, ApoB and SR-B1, consistent with our earlier report that expression of glucose and fatty acid transporter genes was also unchanged in diabetic pregnancy-derived yolk sacs. Colocalization of lipid droplets with lysosomes was significantly reduced in the yolk sacs from diabetic and obese pregnancies compared to yolk sacs from normal pregnancies. We therefore conclude that processing of lipids is defective in pregnancies affected by maternal metabolic disease, which may lead to reduced availability of lipids to the developing embryo. The possible implications of insufficient supply of lipids -and potentially of other nutrients-to the embryos experiencing adverse pregnancy conditions are discussed.

Identification of de novo variants in nonsyndromic cleft lip with/without cleft palate patients with low polygenic risk scores

BACKGROUND

Nonsyndromic cleft lip with/without cleft palate (nsCL/P) is a congenital malformation of multifactorial etiology. Research has identified >40 genome-wide significant risk loci, which explain less than 40% of nsCL/P heritability. Studies show that some of the hidden heritability is explained by rare penetrant variants.

METHODS

To identify new candidate genes, we searched for highly penetrant de novo variants (DNVs) in 50 nsCL/P patient/parent-trios with a low polygenic risk for the phenotype (discovery). We prioritized DNV-carrying candidate genes from the discovery for resequencing in independent cohorts of 1010 nsCL/P patients of diverse ethnicities and 1574 population-matched controls (replication). Segregation analyses and rare variant association in the replication cohort, in combination with additional data (genome-wide association data, expression, protein-protein-interactions), were used for final prioritization.

CONCLUSION

In the discovery step, 60 DNVs were identified in 60 genes, including a variant in the established nsCL/P risk gene CDH1. Re-sequencing of 32 prioritized genes led to the identification of 373 rare, likely pathogenic variants. Finally, MDN1 and PAXIP1 were prioritized as top candidates. Our findings demonstrate that DNV detection, including polygenic risk score analysis, is a powerful tool for identifying nsCL/P candidate genes, which can also be applied to other multifactorial congenital malformations.

Gene dosage changes in KCTD13 result in penile and testicular anomalies via diminished androgen receptor function

Despite the high prevalence of hypospadias and cryptorchidism, the genetic basis for these conditions is only beginning to be understood. Using array-comparative-genomic-hybridization (aCGH), potassium-channel-tetramerization-domain-containing-13 (KCTD13) encoded at 16p11.2 was identified as a candidate gene involved in hypospadias, cryptorchidism and other genitourinary (GU) tract anomalies. Copy number variants (CNVs) at 16p11.2 are among the most common syndromic genomic variants identified to date. Many patients with CNVs at this locus exhibit GU and/or neurodevelopmental phenotypes. KCTD13 encodes a substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3-ubiquitin-protein-ligase complex (BCR (BTB-CUL3-RBX1) E3-ubiquitin-protein-ligase complex (B-cell receptor (BCR) [BTB (the BTB domain is a conserved motif involved in protein-protein interactions) Cullin3 complex RING protein Rbx1] E3-ubiqutin-protein-ligase complex), which has essential roles in the regulation of cellular cytoskeleton, migration, proliferation, and neurodevelopment; yet its role in GU development is unknown. The prevalence of KCTD13 CNVs in patients with GU anomalies (2.58%) is significantly elevated when compared with patients without GU anomalies or in the general population (0.10%). KCTD13 is robustly expressed in the developing GU tract. Loss of KCTD13 in cell lines results in significantly decreased levels of nuclear androgen receptor (AR), suggesting that loss of KCTD13 affects AR sub-cellular localization. Kctd13 haploinsufficiency and homozygous deletion in mice cause a significant increase in the incidence of cryptorchidism and micropenis. KCTD13-deficient mice exhibit testicular and penile abnormalities together with significantly reduced levels of nuclear AR and SOX9. In conclusion, gene-dosage changes of murine Kctd13 diminish nuclear AR sub-cellular localization, as well as decrease SOX9 expression levels which likely contribute in part to the abnormal GU tract development in Kctd13 mouse models and in patients with CNVs in KCTD13.

PTIP-Associated Protein 1: More Than a Component of the MLL3/4 Complex

PTIP-associated protein 1 (PA1) is a unique component of MLL3/4 complexes, which are important mammalian histone 3 lysine 4 (H3K4) methyltransferases. PA1 has generated research interest due to its involvement in many essential biological processes such as adipogenesis, B cell class switch recombination, spermatogenesis, and embryonic development. In addition to the classical role of PA1 in H3K4 methylation, non-classical functions have also been discovered in recent studies. In this review, we systematically summarize the expression pattern of PA1 protein in humans and sort the specific molecular mechanism of PA1 in various biological processes. Meanwhile, we provide some new perspectives on the role of PA1 for future studies. A comprehensive understanding of the biological functions and molecular mechanisms of PA1 will facilitate the investigation of its complicated roles in transcriptional regulation.

PA1 participates in the maintenance of blood-testis barrier integrity via cooperation with JUN in the Sertoli cells of mice

Background

The blood–testis barrier (BTB) is essential to the microenvironment of spermatogenesis, and Sertoli cells provide the cellular basis for BTB construction. Numerous nuclear transcription factors have been identified to be vital for the proper functioning of Sertoli cells. PA1 has been reported to play important roles during diverse biological processes, yet its potential function in male reproduction is still unknown.

Results

Here, we show that PA1 was highly expressed in human and mouse testis and predominantly localized in the nuclei of Sertoli cells. Sertoli cell-specific Pa1 knockout resulted in an azoospermia-like phenotype in mice. The knockout of this gene led to multiple defects in spermatogenesis, such as the disorganization of the cytoskeleton during basal and apical ectoplasmic specialization and the disruption of the BTB. Further transcriptomic analysis, together with Cut-Tag results of PA1 in Sertoli cells, revealed that PA1 could affect the expression of a subset of genes that are essential for the normal function of Sertoli cells, including those genes associated with actin organization and cellular junctions such as Connexin43 (Cx43). We further demonstrated that the expression of Cx43 depended on the interaction between JUN, one of the AP-1 complex transcription factors, and PA1.

Conclusion

Overall, our findings reveal that PA1 is essential for the maintenance of BTB integrity in Sertoli cells and regulates BTB construction-related gene expression via transcription factors. Thus, this newly discovered mechanism in Sertoli cells provides a potential diagnostic or even therapeutic target for some individuals with azoospermia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00773-y.

Bi-allelic PAGR1 variants are associated with microcephaly and a severe neurodevelopmental disorder: Genetic evidence from two families

Exome and genome sequencing were used to identify the genetic etiology of a severe neurodevelopmental disorder in two unrelated Ashkenazi Jewish families with three affected individuals. The clinical findings included a prenatal presentation of microcephaly, polyhydramnios and clenched hands while postnatal findings included microcephaly, severe developmental delay, dysmorphism, neurologic deficits, and death in infancy. A shared rare homozygous, missense variant (c.274A > G; p.Ser92Gly, NM_024516.4) was identified in PAGR1, a gene currently not associated with a Mendelian disease. PAGR1 encodes a component of the histone methyltransferase MLL2/MLL3 complex and may function in the DNA damage response pathway. Complete knockout of the murine Pagr1a is embryonic-lethal. Given the available evidence, PAGR1 is a strong candidate gene for a novel autosomal recessive severe syndromic neurodevelopmental disorder.

Dissecting protein domain variability in the core RNA interference machinery of five insect orders

RNA interference (RNAi)-mediated gene silencing can be used to control specific insect pest populations. Unfortunately, the variable efficiency in the knockdown levels of target genes has narrowed the applicability of this technology to a few species. Here, we examine the current state of knowledge regarding the miRNA (micro RNA) and siRNA (small interfering RNA) pathways in insects and investigate the structural variability at key protein domains of the RNAi machinery. Our goal was to correlate domain variability with mechanisms affecting the gene silencing efficiency. To this end, the protein domains of 168 insect species, encompassing the orders Coleoptera, Diptera, Hemiptera, Hymenoptera, and Lepidoptera, were analysed using our pipeline, which takes advantage of meticulous structure-based sequence alignments. We used phylogenetic inference and the evolutionary rate coefficient (K) to outline the variability across domain regions and surfaces. Our results show that four domains, namely dsrm, Helicase, PAZ and Ribonuclease III, are the main contributors of protein variability in the RNAi machinery across different insect orders. We discuss the potential roles of these domains in regulating RNAi-mediated gene silencing and the role of loop regions in fine-tuning RNAi efficiency. Additionally, we identified several order-specific singularities which indicate that lepidopterans have evolved differently from other insect orders, possibly due to constant coevolution with plants and viruses. In conclusion, our results highlight several variability hotspots that deserve further investigation in order to improve the application of RNAi technology in the control of insect pests.

COMPASS and SWI/SNF complexes in development and disease

The Trithorax group (TrxG) of proteins is a large family of epigenetic regulators that form multiprotein complexes to counteract repressive developmental gene expression programmes established by the Polycomb group of proteins and to promote and maintain an active state of gene expression. Recent studies are providing new insights into how two crucial families of the TrxG - the COMPASS family of histone H3 lysine 4 methyltransferases and the SWI/SNF family of chromatin remodelling complexes - regulate gene expression and developmental programmes, and how misregulation of their activities through genetic abnormalities leads to pathologies such as developmental disorders and malignancies.

MLL3/MLL4-Associated PAGR1 Regulates Adipogenesis by Controlling Induction of C/EBPβ and C/EBPδ

Transcription factors C/EBPβ and C/EBPδ are induced within hours after initiation of adipogenesis in culture. They directly promote the expression of master adipogenic transcription factors peroxisome proliferator-activated receptor γ (PPARγ) and C/EBPα and are required for adipogenesis in vivo However, the mechanism that controls the induction of C/EBPβ and C/EBPδ remains elusive. We previously showed that histone methyltransferases MLL3/MLL4 and associated PTIP are required for the induction of PPARγ and C/EBPα during adipogenesis. Here, we show MLL3/MLL4/PTIP-associated protein PAGR1 (also known as PA1) cooperates with phosphorylated CREB and ligand-activated glucocorticoid receptor to directly control the induction of C/EBPβ and C/EBPδ in the early phase of adipogenesis. Deletion of Pagr1 in white and brown preadipocytes prevents the induction of C/EBPβ and C/EBPδ and leads to severe defects in adipogenesis. Adipogenesis defects in PAGR1-deficient cells can be rescued by the ectopic expression of C/EBPβ or PPARγ. Finally, the deletion of Pagr1 in Myf5⁺ precursor cells impairs brown adipose tissue and muscle development. Thus, by controlling the induction of C/EBPβ and C/EBPδ, PAGR1 plays a critical role in adipogenesis.

KMT2C/D COMPASS complex-associated diseases [KCDCOM-ADs]: an emerging class of congenital regulopathies

The type 2 lysine methyltransferases KMT2C and KMT2D are large, enzymatically active scaffold proteins that form the core of nuclear regulatory structures known as KMT2C/D COMPASS complexes (complex of proteins associating with Set1). These evolutionarily conserved proteins regulate DNA promoter and enhancer elements, modulating the activity of diverse cell types critical for embryonic morphogenesis, central nervous system development, and post-natal survival. KMT2C/D COMPASS complexes and their binding partners enhance active gene expression of specific loci via the targeted modification of histone-3 tail residues, in general promoting active euchromatic conformations. Over the last 20 years, mutations in five key COMPASS complex genes have been linked to three human congenital syndromes: Kabuki syndrome (type 1 [KMT2D] and 2 [KDM6A]), Rubinstein-Taybi syndrome (type 1 [CBP] and 2 [EP300]), and Kleefstra syndrome type 2 (KMT2C). Here, we review the composition and biochemical function of the KMT2 complexes. The specific cellular and embryonic roles of the KMT2C/D COMPASS complex are highlight with a focus on clinically relevant mechanisms sensitive to haploinsufficiency. The phenotypic similarities and differences between the members of this new family of disorders are outlined and emerging therapeutic strategies are detailed.

Long non-coding RNA PAXIP1-AS1 facilitates cell invasion and angiogenesis of glioma by recruiting transcription factor ETS1 to upregulate KIF14 expression

Background

Gliomas are common life-threatening cancers, mainly due to their aggressive nature and frequent invasiveness and long non-coding RNAs (lncRNAs) are emerging as promising molecular targets. Therefore, we explored the regulatory mechanisms underlying the putative involvement of the lncRNA PAX-interacting protein 1- antisense RNA1/ETS proto-oncogene 1/kinesin family member 14 (PAXIP1-AS1/ETS1/KIF14) axis in glioma cell invasion and angiogenesis.

Methods

Firstly, we identified differentially expressed lncRNA PAXIP1-AS1 as associated with glioma based on bioinformatic data. Then, validation experiments were conducted to confirm a high expression level of lncRNA PAXIP1-AS1 in glioma tissues and cells, accompanied by upregulated KIF14. We further examined the binding between lncRNA PAXIP1-AS1, KIF14 promoter activity, and transcription factor ETS1. Next, overexpression vectors and shRNAs were delivered to alter the expression of lncRNA PAXIP1-AS1, KIF14, and ETS1 to analyze their effects on glioma progression in vivo and in vitro.

Results

LncRNA PAXIP1-AS1 was mainly distributed in the nucleus of glioma cells. LncRNA PAXIP1-AS1 could upregulate the KIF14 promoter activity by recruiting transcription factor ETS1. Overexpression of lncRNA PAXIP1-AS1 enhanced migration, invasion, and angiogenesis of human umbilical vein endothelial cells in glioma by recruiting the transcription factor ETS1 to upregulate the expression of KIF14, which was further confirmed by accelerated tumor growth in nude mice.

Conclusions

The key findings of this study highlighted the potential of the lncRNA PAXIP1-AS1/ETS1/KIF14 axis as a therapeutic target for glioma treatment, due to its role in controlling the migration and invasion of glioma cells and its angiogenesis.

An interaction-based model for neuropsychiatric features of copy-number variants

Variably expressive copy-number variants (CNVs) are characterized by extensive phenotypic heterogeneity of neuropsychiatric phenotypes. Approaches to identify single causative genes for these phenotypes within each CNV have not been successful. Here, we posit using multiple lines of evidence, including pathogenicity metrics, functional assays of model organisms, and gene expression data, that multiple genes within each CNV region are likely responsible for the observed phenotypes. We propose that candidate genes within each region likely interact with each other through shared pathways to modulate the individual gene phenotypes, emphasizing the genetic complexity of CNV-associated neuropsychiatric features.

Transgenerational Inheritance of DNA Hypomethylation in Daphnia magna in Response to Salinity Stress

Epigenetic mechanisms have been found to play important roles in environmental stress response and regulation. These can, theoretically, be transmitted to future unexposed generations, yet few studies have shown persisting stress-induced transgenerational effects, particularly in invertebrates. Here, we focus on the aquatic microcrustacean Daphnia, a parthenogenetic model species, and its response to salinity stress. Salinity is a serious threat to freshwater ecosystems and a relevant form of environmental perturbation affecting freshwater ecosystems. We exposed one generation of D. magna to high levels of salinity (F0) and found that the exposure provoked specific methylation patterns that were transferred to the three consequent nonexposed generations (F1, F2, and F3). This was the case for the hypomethylation of six protein-coding genes with important roles in the organisms' response to environmental change: DNA damage repair, cytoskeleton organization, and protein synthesis. This suggests that epigenetic changes in Daphnia are particularly targeted to genes involved in coping with general cellular stress responses. Our results highlight that epigenetic marks are affected by environmental stressors and can be transferred to subsequent unexposed generations. Epigenetic marks could therefore prove to be useful indicators of past or historic pollution in this parthenogenetic model system. Furthermore, no life history costs seem to be associated with the maintenance of hypomethylation across unexposed generations in Daphnia following a single stress exposure.

Amniotic ectoderm expansion in mouse occurs via distinct modes and requires SMAD5-mediated signalling

Upon gastrulation, the mammalian conceptus transforms rapidly from a simple bilayer into a multilayered embryo enveloped by its extra-embryonic membranes. Impaired development of the amnion, the innermost membrane, causes major malformations. To clarify the origin of the mouse amnion, we used single-cell labelling and clonal analysis. We identified four clone types with distinct clonal growth patterns in amniotic ectoderm. Two main types have progenitors in extreme proximal-anterior epiblast. Early descendants initiate and expand amniotic ectoderm posteriorly, while descendants of cells remaining anteriorly later expand amniotic ectoderm from its anterior side. Amniogenesis is abnormal in embryos deficient in the bone morphogenetic protein (BMP) signalling effector SMAD5, with delayed closure of the proamniotic canal, and aberrant amnion and folding morphogenesis. Transcriptomics of individual Smad5 mutant amnions isolated before visible malformations and tetraploid chimera analysis revealed two amnion defect sets. We attribute them to impairment of progenitors of the two main cell populations in amniotic ectoderm and to compromised cuboidal-to-squamous transition of anterior amniotic ectoderm. In both cases, SMAD5 is crucial for expanding amniotic ectoderm rapidly into a stretchable squamous sheet to accommodate exocoelom expansion, axial growth and folding morphogenesis.

Genetic and biochemical evidence that gastrulation defects in Pofut2 mutants result from defects in ADAMTS9 secretion

Protein O-fucosyltransferase 2 (POFUT2) adds O-linked fucose to Thrombospondin Type 1 Repeats (TSR) in 49 potential target proteins. Nearly half the POFUT2 targets belong to the A Disintegrin and Metalloprotease with ThromboSpondin type-1 motifs (ADAMTS) or ADAMTS-like family of proteins. Both the mouse Pofut2 RST434 gene trap allele and the Adamts9 knockout were reported to result in early embryonic lethality, suggesting that defects in Pofut2 mutant embryos could result from loss of O-fucosylation on ADAMTS9. To address this question, we compared the Pofut2 and Adamts9 knockout phenotypes and used Cre-mediated deletion of Pofut2 and Adamts9 to dissect the tissue-specific role of O-fucosylated ADAMTS9 during gastrulation. Disruption of Pofut2 using the knockout (LoxP) or gene trap (RST434) allele, as well as deletion of Adamts9, resulted in disorganized epithelia (epiblast, extraembryonic ectoderm, and visceral endoderm) and blocked mesoderm formation during gastrulation. The similarity between Pofut2 and Adamts9 mutants suggested that disruption of ADAMTS9 function could be responsible for the gastrulation defects observed in Pofut2 mutants. Consistent with this prediction, CRISPR/Cas9 knockout of POFUT2 in HEK293T cells blocked secretion of ADAMTS9. We determined that Adamts9 was dynamically expressed during mouse gastrulation by trophoblast giant cells, parietal endoderm, the most proximal visceral endoderm adjacent to the ectoplacental cone, extraembryonic mesoderm, and anterior primitive streak. Conditional deletion of either Pofut2 or Adamts9 in the epiblast rescues the gastrulation defects, and identified a new role for O-fucosylated ADAMTS9 during morphogenesis of the amnion and axial mesendoderm. Combined, these results suggested that loss of ADAMTS9 function in the extra embryonic tissue is responsible for gastrulation defects in the Pofut2 knockout. We hypothesize that loss of ADAMTS9 function in the most proximal visceral endoderm leads to slippage of the visceral endoderm and altered characteristics of the extraembryonic ectoderm. Consequently, loss of input from the extraembryonic ectoderm and/or compression of the epiblast by Reichert's membrane blocks gastrulation. In the future, the Pofut2 and Adamts9 knockouts will be valuable tools for understanding how local changes in the properties of the extracellular matrix influence the organization of tissues during mammalian development.

Structural D/E-rich repeats play multiple roles especially in gene regulation through DNA/RNA mimicry

Aspartic acid and glutamic acid repeats in proteins exhibit strong negative charge distribution and they may play special biological roles. From 39,684 unique structural data in the RCSB Protein Data Bank (PDB), 173 structures were found to contain ordered D/E-rich repeat structures, and 57 of them were related to DNA/RNA functions. The frequency of occurrence of glutamic acid (36.90%) was higher than that of aspartic acid (27.02%). Glycine (2.38%), alanine (2.68%), valine (3.54%), leucine (5.57%), and isoleucine (3.34%), but not methionine (0.91%), were the most abundant hydrophobic residues. The available complex structures suggested that D/E-rich proteins might be involved in DNA mimicry, mRNA processing and regulation of the transcription complex. The region surrounding the D/E-rich repeat sequences plays important roles in the binding specificity toward the target proteins. The numbers and composition of aspartic acid and glutamic acid might also affect binding properties. Aspartic acid and glutamic acid are disorder-promoting residues in the intrinsically disorder proteins. Our findings suggest that the D/E-rich repeats are unique components of intrinsically disordered proteins, which are involved in the gene regulation and could serve as potential druggable fragments or drug targets.

A PTIP-PA1 subcomplex promotes transcription for IgH class switching independently from the associated MLL3/MLL4 methyltransferase complex

Transcription at the immunoglobulin heavy chain (Igh) locus targets class switch recombination (CSR)-associated DNA damage and is promoted by the BRCT domain-containing PTIP protein. Starnes et al. found that PTIP functions in transcription and CSR separately from its association with the MLL3/MLL4 complex and from its localization to sites of DNA damage.

Class switch recombination (CSR) diversifies antibodies for productive immune responses while maintaining stability of the B-cell genome. Transcription at the immunoglobulin heavy chain (Igh) locus targets CSR-associated DNA damage and is promoted by the BRCT domain-containing PTIP (Pax transactivation domain-interacting protein). Although PTIP is a unique component of the mixed-lineage leukemia 3 (MLL3)/MLL4 chromatin-modifying complex, the mechanisms for how PTIP promotes transcription remain unclear. Here we dissected the minimal structural requirements of PTIP and its different protein complexes using quantitative proteomics in primary lymphocytes. We found that PTIP functions in transcription and CSR separately from its association with the MLL3/MLL4 complex and from its localization to sites of DNA damage. We identified a tandem BRCT domain of PTIP that is sufficient for CSR and identified PA1 as its main functional protein partner. Collectively, we provide genetic and biochemical evidence that a PTIP–PA1 subcomplex functions independently from the MLL3/MLL4 complex to mediate transcription during CSR. These results further our understanding of how multifunctional chromatin-modifying complexes are organized by subcomplexes that harbor unique and distinct activities.

Nodal signaling from the visceral endoderm is required to maintain Nodal gene expression in the epiblast and drive DVE/AVE migration

In the early mouse embryo, a specialized population of extraembryonic visceral endoderm (VE) cells called the distal VE (DVE) arises at the tip of the egg cylinder stage embryo and then asymmetrically migrates to the prospective anterior, recruiting additional distal cells. Upon migration these cells, called the anterior VE (AVE), establish the anterior posterior (AP) axis by restricting gastrulation-inducing signals to the opposite pole. The Nodal-signaling pathway has been shown to have a critical role in the generation and migration of the DVE/AVE. The Nodal gene is expressed in both the VE and in the pluripotent epiblast, which gives rise to the germ layers. Previous findings have provided conflicting evidence as to the relative importance of Nodal signaling from the epiblast vs. VE for AP patterning. Here we show that conditional mutagenesis of the Nodal gene specifically within the VE leads to reduced Nodal expression levels in the epiblast and incomplete or failed DVE/AVE migration. These results support a required role for VE Nodal to maintain normal levels of expression in the epiblast, and suggest signaling from both VE and epiblast is important for DVE/AVE migration.