Huber TL et al. (2001), neptune, a Krüppel-like transcription factor th...

XB-ART-8368

Curr Biol 2001 Sep 18;1118:1456-61. doi: 10.1016/s0960-9822(01)00427-4.

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neptune, a Krüppel-like transcription factor that participates in primitive erythropoiesis in Xenopus.

Huber TL , Perkins AC , Deconinck AE , Chan FY , Mead PE , Zon LI .

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The specification of the erythroid lineage from hematopoietic stem cells requires the expression and activity of lineage-specific transcription factors. One transcription factor family that has several members involved in hematopoiesis is the Krüppel-like factor (KLF) family [1]. For example, erythroid KLF (EKLF) regulates beta-globin expression during erythroid differentiation [2-6]. KLFs share a highly conserved zinc finger-based DNA binding domain (DBD) that mediates binding to CACCC-box and GC-rich sites, both of which are frequently found in the promoters of hematopoietic genes. Here, we identified a novel Xenopus KLF gene, neptune, which is highly expressed in the ventral blood island (VBI), cranial ganglia, and hatching and cement glands. neptune expression is induced in response to components of the BMP-4 signaling pathway in injected animal cap explants. Similar to its family member, EKLF, Neptune can bind CACCC-box and GC-rich DNA elements. We show that Neptune cooperates with the hematopoietic transcription factor XGATA-1 to enhance globin induction in animal cap explants. A fusion protein comprised of Neptune's DBD and the Drosophila engrailed repressor domain suppresses the induction of globin in ventral marginal zones and in animal caps. These studies demonstrate that Neptune is a positive regulator of primitive erythropoiesis in Xenopus.

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Species referenced: Xenopus
Genes referenced: klf17 klf4

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	Figure 2. neptune is expressed in the hatching gland, cement gland, and prospective VBI. (a) A stage-11 embryo, dorsal is to the right. neptune is expressed in the ectoderm of the animal pole but is being excluded from the future neural plate. Arrowheads show the location of the blastopore lip on the dorsal and ventral sides. (b) At stage 12, neptune is expressed in the cement gland primordium. At (c) stage 18 and (d) stage 22, there is expression in the cement and hatching glands. (b)–(d) are anterior views of the embryos. (e) A dorsal view of a stage-15 embryo shows ectodermal expression along the edge of the neural folds. (f,g) Tailbud stages. (h) and (i) show expression in the VII and IX cranial ganglia in stage-25 and stage-31 embryos, respectively. Ventral views of (j) stage-22 and (k) stage-25 embryos show expression in the VBI and around the remnant of the blastopore. neptune expression is excluded from the liver anlage (LA). (l) A lateral view of a stage-31 embryo. (m) Stage-37/38 embryo with circulating cells expressing neptune
	klf17 ( KLF transcription factor 17) gene expression in Xenopus laevis embryos, NF stage 11, as assayed by in situ hybridization, lateral view, animal side up.
	klf17 (KLF transcription factor 17) gene expression in Xenopus laevis embryos, NF stage 22, as assayed by in situ hybridization, anterior view, dorsal up. Image extracted from XB-IMG-46882.
	klf17 ( KLF transcription factor 17) gene expression in Xenopus laevis embryos, NF stage 25, as assayed by in situ hybridization, lateral view, anterior left, dorsal up.
	klf17 ( KLF transcription factor 17) gene expression in Xenopus laevis embryos, NF stage 31, as assayed by in situ hybridization, lateral view, anterior left, dorsal up.