Transcription dynamics of endodermal organ formation

Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Developmental Dynamics (Impact Factor: 2.38). 01/2009; 238(1):29-42. DOI: 10.1002/dvdy.21810
Source: PubMed


Although endodermal organs including the liver, pancreas, and intestine are of significant therapeutic interest, the mechanism by which the endoderm is divided into organ domains during embryogenesis is not well understood. To better understand this process, global gene expression profiling was performed on early endodermal organ domains. This global analysis was followed up by dynamic immunofluorescence analysis of key transcription factors, uncovering novel expression patterns as well as cell surface proteins that allow prospective isolation of specific endodermal organ domains. Additionally, a repressive interaction between Cdx2 and Sox2 was found to occur at the prospective stomach-intestine border, with the hepatic and pancreatic domains forming at this boundary, and Hlxb9 was revealed to have graded expression along the dorsal-ventral axis. These results contribute to understanding the mechanism of endodermal organogenesis and should assist efforts to replicate this process using pluripotent stem cells.

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    • "The temporal colinearity of amphioxus ParaHox genes is also evident, but inverted with respect to the pattern in the Hox cluster: transcript of the posterior Cdx is detected first and the anterior Gsx is expressed last [22]. Studies on the expression of ParaHox genes in other deuterostome and protostome animals including sea urchin [20], ascidian [23-26], mouse [27-29], polychaete worms [17,30,31], and gastropod [32] have also shown similar expression domains: Gsx genes are mostly expressed solely in the central nervous system (CNS) with a rostral anterior limit; Xlox genes are expressed both in the CNS and the central regions of developing guts, such as the pancreas of vertebrates; Cdx genes are expressed in more posterior regions of the CNS and gut. Temporal colinearity, on the other hand, is reversed in S. purpuratus and lost in C. intestinalis[33]. "
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    ABSTRACT: ParaHox and Hox genes are thought to have evolved from a common ancestral ProtoHox cluster or from tandem duplication prior to the divergence of cnidarians and bilaterians. Similar to Hox clusters, chordate ParaHox genes including Gsx, Xlox, and Cdx, are clustered and their expression exhibits temporal and spatial colinearity. In non-chordate animals, however, studies on the genomic organization of ParaHox genes are limited to only a few animal taxa. Hemichordates, such as the Enteropneust acorn worms, have been used to gain insights into the origins of chordate characters. In this study, we investigated the genomic organization and expression of ParaHox genes in the indirect developing hemichordate acorn worm Ptychodera flava. We found that P. flava contains an intact ParaHox cluster with a similar arrangement to that of chordates. The temporal expression order of the P. flava ParaHox genes is the same as that of the chordate ParaHox genes. During embryogenesis, the spatial expression pattern of PfCdx in the posterior endoderm represents a conserved feature similar to the expression of its orthologs in other animals. On the other hand, PfXlox and PfGsx show a novel expression pattern in the blastopore. Nevertheless, during metamorphosis, PfXlox and PfCdx are expressed in the endoderm in a spatially staggered pattern similar to the situation in chordates. Our study shows that P. flava ParaHox genes, despite forming an intact cluster, exhibit temporal colinearity but lose spatial colinearity during embryogenesis. During metamorphosis, partial spatial colinearity is retained in the transforming larva. These results strongly suggest that intact ParaHox gene clustering was retained in the deuterostome ancestor and is correlated with temporal colinearity.
    BMC Evolutionary Biology 06/2013; 13(1):129. DOI:10.1186/1471-2148-13-129 · 3.37 Impact Factor
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    • "Using Tg(−5mnx1:tagRFP), we found that overnutrition increased the number of TagRFP-positive β-cells from 17.1 ± 2.4 cells in the unfed larvae (n = 16) (Fig. 5A) to 23.3 ± 5.3 cells in larvae overfed egg yolk for 8 h (Fig. 5B) (n = 30) (t test, P < 0.001). Although highly expressed during early development (data not shown) (36,37), TagRFP was expressed only in a subset of the β-cells in the larval islet (Fig. 5A and B). The increase in TagRFP-positive cells likely highlights newly differentiated, immature β-cells. "
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    ABSTRACT: Persistent nutrient excess results in a compensatory increase in the β-cell number in mammals. It is unknown whether this response occurs in nonmammalian vertebrates, including zebrafish, a model for genetics and chemical genetics. We investigated the response of zebrafish β-cells to nutrient excess and the underlying mechanisms by culturing transgenic zebrafish larvae in solutions of different nutrient composition. The number of β-cells rapidly increases after persistent, but not intermittent, exposure to glucose or a lipid-rich diet. The response to glucose, but not the lipid-rich diet, required mammalian target of rapamycin activity. In contrast, inhibition of insulin/IGF-1 signaling in β-cells blocked the response to the lipid-rich diet, but not to glucose. Lineage tracing and marker expression analyses indicated that the new β-cells were not from self-replication but arose through differentiation of postmitotic precursor cells. On the basis of transgenic markers, we identified two groups of newly formed β-cells: one with nkx2.2 promoter activity and the other with mnx1 promoter activity. Thus, nutrient excess in zebrafish induces a rapid increase in β-cells though differentiation of two subpopulations of postmitotic precursor cells. This occurs through different mechanisms depending on the nutrient type and likely involves paracrine signaling between the differentiated β-cells and the precursor cells.
    Diabetes 06/2012; 61(10):2517-24. DOI:10.2337/db11-1841 · 8.10 Impact Factor
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    • "No specific markers of lung lineage have been described in the embryo to confirm the existence of primordial Nkx2-1 + lung progenitors between E9.0, their moment of identifiable lineage specification from endoderm, and E10.5, when the earliest specific lung epithelial marker, SPC, is first expressed. Two transcription factors known to be expressed nonspecifically in early lung endoderm progenitors, Foxp2 and Id2 (Rawlins et al., 2009; Sherwood et al., 2009), were expressed in Nkx2- 1 GFP+ cells (Figure S5); however, both markers were also expressed in GFP À cells. "
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    ABSTRACT: Two populations of Nkx2-1(+) progenitors in the developing foregut endoderm give rise to the entire postnatal lung and thyroid epithelium, but little is known about these cells because they are difficult to isolate in a pure form. We demonstrate here the purification and directed differentiation of primordial lung and thyroid progenitors derived from mouse embryonic stem cells (ESCs). Inhibition of TGFβ and BMP signaling, followed by combinatorial stimulation of BMP and FGF signaling, can specify these cells efficiently from definitive endodermal precursors. When derived using Nkx2-1(GFP) knockin reporter ESCs, these progenitors can be purified for expansion in culture and have a transcriptome that overlaps with developing lung epithelium. Upon induction, they can express a broad repertoire of markers indicative of lung and thyroid lineages and can recellularize a 3D lung tissue scaffold. Thus, we have derived a pure population of progenitors able to recapitulate the developmental milestones of lung/thyroid development.
    Cell stem cell 04/2012; 10(4):398-411. DOI:10.1016/j.stem.2012.01.019 · 22.27 Impact Factor
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