Homeobox Protein HB24 is a protein that in humans is encoded by the HLX gene. [5] [6] [7]
Homeobox Protein HB24 is a protein that in humans is encoded by the HLX gene. [5] [6] [7]
Hlx belongs to the class of homeobox transcription factors, initially cloned from a B-lymphocyte cell line. [8] Targeted knockout of the gene has demonstrated its vital role in liver and gut organogenesis. [9] Its expression is first noticed in embryonic day 9.5 (E9.5) in the splanchnic mesoderm caudal to the level of the heart and foregut pocket, and in the branchial arches. Around E10- E12.5, the expression becomes more prominent in the mesenchyme of the visceral organs of the gut such as liver, intestines and gall bladder. [10] Hlx is essential for liver and gut expansion, but not for onset of their development. Heterozygous knockouts of Hlx (Hlx +/−) are normal whereas homozygous knockouts (Hlx −/–) develop severe hypoplasia of the liver and gut along with anaemia. Hlx controls the epithelial-mesenchymal interaction necessary for liver and gut expansion. [9] At E8.0, the primary liver bud is formed from the midgut endoderm in response to signals from the cardiogenic mesoderm. This is followed by signals from the septum transversum that induce epithelial-mesenchymal transition in the hepatic progenitors of the gut endoderm. [11] [12] In a third stage, these signaling factors induce the liver endoderm to undergo proliferation and form liver cords. The same factor controls gut proliferation, and Hlx governs its expression. Although these mice develop anaemia, it is likely due to insufficient support from the liver in producing matrix component needed for hematopoiesis rather than an intrinsic defect in the hematopoietic cells. [9]
PDX1, also known as insulin promoter factor 1, is a transcription factor in the ParaHox gene cluster. In vertebrates, Pdx1 is necessary for pancreatic development, including β-cell maturation, and duodenal differentiation. In humans this protein is encoded by the PDX1 gene, which was formerly known as IPF1. The gene was originally identified in the clawed frog Xenopus laevis and is present widely across the evolutionary diversity of bilaterian animals, although it has been lost in evolution in arthropods and nematodes. Despite the gene name being Pdx1, there is no Pdx2 gene in most animals; single-copy Pdx1 orthologs have been identified in all mammals. Coelacanth and cartilaginous fish are, so far, the only vertebrates shown to have two Pdx genes, Pdx1 and Pdx2.
Homeobox protein Hox-A9 is a protein that in humans is encoded by the HOXA9 gene.
HNF1 homeobox B, also known as HNF1B or transcription factor 2 (TCF2), is a human gene.
Homeobox protein Hox-B6 is a protein that in humans is encoded by the HOXB6 gene.
Hematopoietically-expressed homeobox protein HHEX is a protein that in humans is encoded by the HHEX gene and also known as Proline Rich Homeodomain protein PRH.
Homeobox protein Hox-B5 is a protein that in humans is encoded by the HOXB5 gene.
Homeobox protein Hox-C8 is a protein that in humans is encoded by the HOXC8 gene.
T-cell leukemia homeobox protein 1 is a protein that in humans is encoded by the TLX1 gene, which was initially named HOX11.
Homeobox protein Hox-B9 is a protein that in humans is encoded by the HOXB9 gene.
Homeobox protein Hox-D3 is a protein that in humans is encoded by the HOXD3 gene.
Homeobox protein DLX-4 is a protein that in humans is encoded by the DLX4 gene.
Homeobox protein Hox-D9 is a protein that in humans is encoded by the HOXD9 gene.
Homeobox protein Hox-C6 is a protein that in humans is encoded by the HOXC6 gene. Hox-C6 expression is highest in the fallopian tube and ovary. HoxC6 has been highly expressed in many types of cancers including prostate, breast, and esophageal squamous cell cancer.
Motor neuron and pancreas homeobox 1 (MNX1), also known as Homeobox HB9 (HLXB9), is a human protein encoded by the MNX1 gene.
Nodal homolog is a secretory protein that in humans is encoded by the NODAL gene which is located on chromosome 10q22.1. It belongs to the transforming growth factor beta superfamily. Like many other members of this superfamily it is involved in cell differentiation in early embryogenesis, playing a key role in signal transfer from the primitive node, in the anterior primitive streak, to lateral plate mesoderm (LPM).
Homeobox protein goosecoid(GSC) is a homeobox protein that is encoded in humans by the GSC gene. Like other homeobox proteins, goosecoid functions as a transcription factor involved in morphogenesis. In Xenopus, GSC is thought to play a crucial role in the phenomenon of the Spemann-Mangold organizer. Through lineage tracing and timelapse microscopy, the effects of GSC on neighboring cell fates could be observed. In an experiment that injected cells with GSC and observed the effects of uninjected cells, GSC recruited neighboring uninjected cells in the dorsal blastopore lip of the Xenopus gastrula to form a twinned dorsal axis, suggesting that the goosecoid protein plays a role in the regulation and migration of cells during gastrulation.
Homeobox protein Hox-A2 is a protein that in humans is encoded by the HOXA2 gene.
The development of the digestive system in the human embryo concerns the epithelium of the digestive system and the parenchyma of its derivatives, which originate from the endoderm. Connective tissue, muscular components, and peritoneal components originate in the mesoderm. Different regions of the gut tube such as the esophagus, stomach, duodenum, etc. are specified by a retinoic acid gradient that causes transcription factors unique to each region to be expressed. Differentiation of the gut and its derivatives depends upon reciprocal interactions between the gut endoderm and its surrounding mesoderm. Hox genes in the mesoderm are induced by a Hedgehog signaling pathway secreted by gut endoderm and regulate the craniocaudal organization of the gut and its derivatives. The gut system extends from the oropharyngeal membrane to the cloacal membrane and is divided into the foregut, midgut, and hindgut.
Mixl1 is a paired-type homeobox transcription factor weighing 27 kDa with 232 amino acids. Mixl1 transcription factor preferentially binds to the DNA sequence TAAT on the Mix gene. Mixl1 is part of the Mix/Bix family of transcription factors, with Mixl1 being the only member identified in humans. The Xenopus Mix gene and human Mix genese are homologues. Mixl1 is functionally similar to the Xenopus Mix.1.
Homeobox protein CDX-4 is a protein that in humans is encoded by the CDX4 gene. This gene is a member of the caudal-related homeobox transcription factor family that also includes CDX1 and CDX2.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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