Project description:Vertebrate embryos elongate the body after gastrulation. Unlike in mice, which elongate both the trunk and tail after gastrulation, zebrafish embryos develop the trunk at the end of gastrulation, followed by tail elongation by proliferation of posteriorly located progenitors. Previous studies have shown that the transcription factors SALL1 and SALL4 redundantly regulate tail elongation in mouse embryos. To test whether sall1a and sall4 also regulate tail elongation in zebrafish, we generated zebrafish mutants for these genes. By 24 hours post-fertilization, sall4 mutant embryos developed normally but exhibited changes in gene expression at the posterior end of the body. sall1a mutants also developed normally by 24 hours post-fertilization. However, embryos mutant for both sall1a and sall4 showed a slight but significant reduction in body length compared to wild-type and sall1a mutant embryos. Our results support a role for sall1a and sall4 in tail elongation in zebrafish, though their contribution appears smaller than that observed in mouse embryos.
Project description:The trunk axial skeleton develops from paraxial mesoderm cells. Our recent study demonstrated that conditional knockout of the stem cell factor Sall4 in mice by TCre caused tail truncation and a disorganized axial skeleton posterior to the lumbar level. Based on this phenotype, we hypothesized that, in addition to the previously reported role of Sall4 in neuromesodermal progenitors, Sall4 is involved in the development of the paraxial mesoderm tissue. ATAC-seq in TCre; Sall4 mutant posterior trunk mesoderm shows that Sall4 knockout reduces chromatin accessibility. We found that Sall4- dependent open chromatin status drives activation and repression of WNT signaling activators and repressors, respectively, to promote WNT signaling. Moreover, footprinting analysis of ATAC-seq data suggests that Sall4-dependent chromatin accessibility facilitates CTCF binding, which contributes to the repression of neural genes within the mesoderm. This study unveils multiple mechanisms by which Sall4 regulates paraxial mesoderm development by directing activation of mesodermal genes and repression of neural genes.
Project description:Deletion of caudal/cdx genes alters hox gene expression and causes defects in posterior tissues and hematopoiesis. Yet, the defects in hox gene expression only partially explain these phenotypes. To gain deeper insight into Cdx4 function, we performed ChIP-seq combined with gene expression profiling in zebrafish, and identified the transcription factor spalt-like 4 (sall4) as a Cdx4 target. ChIP-seq revealed that Sall4 bound to its own gene locus and the cdx4 locus. Expression profiling showed that Cdx4 and Sall4 co-regulate genes such as hox, scl, and lmo2 that initiate hematopoiesis. Combined cdx4/sall4 gene knock-down impairs erythropoiesis, and overexpression of the Cdx4 and Sall4 target genes scl and lmo2 together rescued the erythroid program. These findings suggest that auto- and cross- regulation of Cdx4 and Sall4 establish a stable molecular circuit in mesoderm that facilitates the activation of the blood-specific program as development proceeds.
Project description:Deletion of caudal/cdx genes alters hox gene expression and causes defects in posterior tissues and hematopoiesis. Yet, the defects in hox gene expression only partially explain these phenotypes. To gain deeper insight into Cdx4 function, we performed ChIP-seq combined with gene expression profiling in zebrafish, and identified the transcription factor spalt-like 4 (sall4) as a Cdx4 target. ChIP-seq revealed that Sall4 bound to its own gene locus and the cdx4 locus. Expression profiling showed that Cdx4 and Sall4 co-regulate genes such as hox, scl, and lmo2 that initiate hematopoiesis. Combined cdx4/sall4 gene knock-down impairs erythropoiesis, and overexpression of the Cdx4 and Sall4 target genes scl and lmo2 together rescued the erythroid program. These findings suggest that auto- and cross- regulation of Cdx4 and Sall4 establish a stable molecular circuit in mesoderm that facilitates the activation of the blood-specific program as development proceeds. ChIP-seq was performed against Cdx4, Sall4, H3K27ac, and H3K4me3 in bud-stage zebrafish embryos. Input material was sequenced as controls.
Project description:The vertebrate main-body axis is laid down during embryonic stages in an anterior-to-posterior (head-to-tail) direction, driven and supplied by posteriorly located progenitors. For the vertebral column, the process of axial progenitor cell expansion that drives axis elongation, and the process of segmentation which allocates these progenitors into repeating vertebral units, occurs seemingly uninterrupted from the first to the last vertebra. Nonetheless, there is clear developmental and evolutionary support for two discrete modules controlling processes within different axial regions: a trunk module and a tail module. The secreted signal Gdf11 has been identified as a principal regulator of timing the trunk-to-tail (T-to-T) transition, but has pleiotropic effects across much of the main body axis, highlighting the need to reveal intrinsic regulatory networks that function to exclusively control one or the other module. Here, we identify Nuclear receptor subfamily 6 group A member 1 (Nr6a1) as a master regulator of elongation, patterning and lineage allocation specifically within the trunk region of the mouse. Both gain- and loss-of-function in vivo analysis revealed that the precise level of Nr6a1 acts as a rheostat, expanding or contracting vertebral number of the trunk region autonomously from other axial regions. Moreover, the timely clearance of Nr6a1 observed at the T-to-T transition was essential in allowing the tail module to operate correctly. In parallel with these effects on vertebral number, we show that Nr6a1 controls the timely progression of global Hox signatures within axial progenitors, preventing the precocious expression of multiple posterior Hox genes as the trunk is being laid down and thus reinforcing that patterning and elongation are coordinated. Finally, our data supports a crucial role for Nr6a1 in regulating gene regulatory networks that guide cell lineage choice of axial progenitors between neural and mesodermal fate. Collectively, our data reveals an axially-restricted role for Nr6a1 in all major cellular and tissue-level events required for vertebral column formation, supporting the view that modulation of Nr6a1 expression level or function may underpin evolutionary changes in axial formulae that exclusively alter the trunk region.
Project description:The vertebrate main-body axis is laid down during embryonic stages in an anterior-to-posterior (head-to-tail) direction, driven and supplied by posteriorly located progenitors. For the vertebral column, the process of axial progenitor cell expansion that drives axis elongation, and the process of segmentation which allocates these progenitors into repeating vertebral units, occurs seemingly uninterrupted from the first to the last vertebra. Nonetheless, there is clear developmental and evolutionary support for two discrete modules controlling processes within different axial regions: a trunk module and a tail module. The secreted signal Gdf11 has been identified as a principal regulator of timing the trunk-to-tail (T-to-T) transition, but has pleiotropic effects across much of the main body axis, highlighting the need to reveal intrinsic regulatory networks that function to exclusively control one or the other module. Here, we identify Nuclear receptor subfamily 6 group A member 1 (Nr6a1) as a master regulator of elongation, patterning and lineage allocation specifically within the trunk region of the mouse. Both gain- and loss-of-function in vivo analysis revealed that the precise level of Nr6a1 acts as a rheostat, expanding or contracting vertebral number of the trunk region autonomously from other axial regions. Moreover, the timely clearance of Nr6a1 observed at the T-to-T transition was essential in allowing the tail module to operate correctly. In parallel with these effects on vertebral number, we show that Nr6a1 controls the timely progression of global Hox signatures within axial progenitors, preventing the precocious expression of multiple posterior Hox genes as the trunk is being laid down and thus reinforcing that patterning and elongation are coordinated. Finally, our data supports a crucial role for Nr6a1 in regulating gene regulatory networks that guide cell lineage choice of axial progenitors between neural and mesodermal fate. Collectively, our data reveals an axially-restricted role for Nr6a1 in all major cellular and tissue-level events required for vertebral column formation, supporting the view that modulation of Nr6a1 expression level or function may underpin evolutionary changes in axial formulae that exclusively alter the trunk region.
Project description:Sall4 is a mouse homolog of a causative gene of the autosomal dominant disorder known as Okihiro syndrome. We previously showed that Sall4 absence leads to lethality during peri-implantation and that Sall4-null embryonic stem (ES) cells proliferate poorly with intact pluripotency when cultured on feeder cells. However, a subsequent report indicated that shRNA-mediated Sall4 inhibition in ES cells led to a severe reduction in Oct3/4 and a secondary increase in Cdx2, which resulted in complete differentiation into the trophectoderm when cultured in the feeder-free condition. So we profiled gene expression changes when Sall4 is deleted in ES cells in the presence or absence of feeder cells. key word: embryonic stem (ES) cell, Sall4, feeder
Project description:High confidence SALL4 targets were identified in mESCs by performing Cut&Run on SALL4 Flox/Flox and SALL4 -/- cells. We validated a commercially available antibody that specifically recognizes SALL4 protein.
Project description:SALL4 is a nuclear factor central to the maintenance of stem cell pluripotency and is a key component in HCC, a malignancy with no effective treatment. In cancer cells, SALL4 associates with NuRD to silence tumor suppressor genes such as PTEN. Here, we design a potent therapeutic SALL4 peptide (FFW) capable of antagonizing the SALL4-NURD interaction using systematic truncation and amino acid substitution studies. To understand the pathways affected by the peptide treatment, we performed RNA sequencing on cells treated with different peptides. Furthermore, to identify SALL4 DNA binding targets, we have performed CRUD-ChIP sequencing with SALL4 and H2K27Ac antibodies on HCC cell line SNU398.