Hematopoietically-expressed homeobox protein HHEX is a protein that in humans is encoded by the HHEXgene.
This gene encodes a member of the homeobox family of transcription factors, many of which are involved in developmental processes. Expression in specific hematopoietic lineages suggests that this protein may play a role in hematopoietic differentiation.
The HHEX transcription factor acts as a promoter in some instances and an inhibitor others. It interacts with a number of other signaling molecules to play an important role in the development of multiple organs, such as the liver, thyroid and forebrain. HHEX serves to repress VEGFA, another protein which is important in endothelial cell development. SCL, a significant transcription factor for blood and endothelial cell differentiation, is shown to interact with HHEX to promote the correct development of the hematopoiesis process. HHEX appears to work together with another molecule, β-catenin, for the development of the anterior organizer. It also contributes to developmental remodeling and stabilization of endothelial cells in an unborn organism. The importance of this transcription factor is illustrated by the inability of HHEX knockout mice embryos to survive gestation. Without the expression of HHEX, these mice embryos die in utero between Day 13 and Day 16. HHEX knockout mice display a range of abnormalities including forebrain abnormalities in various levels of severity, as well as a number of other defects including heart, vasculature, liver, monocyte, and thyroid abnormalities.
^Hromas R, Radich J, Collins S (Sep 1993). "PCR cloning of an orphan homeobox gene (PRH) preferentially expressed in myeloid and liver cells". Biochemical and Biophysical Research Communications195 (2): 976–83. doi:10.1006/bbrc.1993.2140. PMID8103988.
^ abMartinez Barbera JP, Clements M, Thomas P, Rodriguez T, Meloy D, Kioussis D, Beddington RS (Jun 2000). "The homeobox gene Hex is required in definitive endodermal tissues for normal forebrain, liver and thyroid formation". Development127 (11): 2433–45. PMID10804184.
^ abcdHallaq H, Pinter E, Enciso J, McGrath J, Zeiss C, Brueckner M, Madri J, Jacobs HC, Wilson CM, Vasavada H, Jiang X, Bogue CW (Oct 2004). "A null mutation of Hhex results in abnormal cardiac development, defective vasculogenesis and elevated Vegfa levels". Development131 (20): 5197–209. doi:10.1242/dev.01393. PMID15459110.
^Liao W, Ho CY, Yan YL, Postlethwait J, Stainier DY (Oct 2000). "Hhex and scl function in parallel to regulate early endothelial and blood differentiation in zebrafish". Development127 (20): 4303–13. PMID11003831.
^Zamparini AL, Watts T, Gardner CE, Tomlinson SR, Johnston GI, Brickman JM (Sep 2006). "Hex acts with beta-catenin to regulate anteroposterior patterning via a Groucho-related co-repressor and Nodal". Development133 (18): 3709–22. doi:10.1242/dev.02516. PMID16936074.
^Topcu Z, Mack DL, Hromas RA, Borden KL (Nov 1999). "The promyelocytic leukemia protein PML interacts with the proline-rich homeodomain protein PRH: a RING may link hematopoiesis and growth control". Oncogene18 (50): 7091–100. doi:10.1038/sj.onc.1203201. PMID10597310.
Neidle S, Goodwin GH (May 1994). "A homology-based molecular model of the proline-rich homeodomain protein Prh, from haematopoietic cells". FEBS Letters345 (2-3): 93–8. doi:10.1016/0014-5793(94)00446-3. PMID7911091.
Manfioletti G, Gattei V, Buratti E, Rustighi A, De Iuliis A, Aldinucci D, Goodwin GH, Pinto A (Mar 1995). "Differential expression of a novel proline-rich homeobox gene (Prh) in human hematolymphopoietic cells". Blood85 (5): 1237–45. PMID7858254.
Topcu Z, Mack DL, Hromas RA, Borden KL (Nov 1999). "The promyelocytic leukemia protein PML interacts with the proline-rich homeodomain protein PRH: a RING may link hematopoiesis and growth control". Oncogene18 (50): 7091–100. doi:10.1038/sj.onc.1203201. PMID10597310.
Schaefer LK, Wang S, Schaefer TS (Nov 2001). "Functional interaction of Jun and homeodomain proteins". The Journal of Biological Chemistry276 (46): 43074–82. doi:10.1074/jbc.M102552200. PMID11551904.
Morgutti M, Demori E, Pecile V, Amoroso A, Rustighi A, Manfioletti G (2001). "Genomic organization and chromosome mapping of the human homeobox gene HHEX". Cytogenetics and Cell Genetics94 (1-2): 30–2. doi:10.1159/000048778. PMID11701950.
D'Elia AV, Tell G, Russo D, Arturi F, Puglisi F, Manfioletti G, Gattei V, Mack DL, Cataldi P, Filetti S, Di Loreto C, Damante G (Mar 2002). "Expression and localization of the homeodomain-containing protein HEX in human thyroid tumors". The Journal of Clinical Endocrinology and Metabolism87 (3): 1376–83. doi:10.1210/jc.87.3.1376. PMID11889211.
Nakagawa T, Abe M, Yamazaki T, Miyashita H, Niwa H, Kokubun S, Sato Y (Feb 2003). "HEX acts as a negative regulator of angiogenesis by modulating the expression of angiogenesis-related gene in endothelial cells in vitro". Arteriosclerosis, Thrombosis, and Vascular Biology23 (2): 231–7. doi:10.1161/01.ATV.0000052670.55321.87. PMID12588764.
George A, Morse HC, Justice MJ (Oct 2003). "The homeobox gene Hex induces T-cell-derived lymphomas when overexpressed in hematopoietic precursor cells". Oncogene22 (43): 6764–73. doi:10.1038/sj.onc.1206822. PMID14555989.
Minami T, Murakami T, Horiuchi K, Miura M, Noguchi T, Miyazaki J, Hamakubo T, Aird WC, Kodama T (May 2004). "Interaction between hex and GATA transcription factors in vascular endothelial cells inhibits flk-1/KDR-mediated vascular endothelial growth factor signaling". The Journal of Biological Chemistry279 (20): 20626–35. doi:10.1074/jbc.M308730200. PMID15016828.
Puppin C, Presta I, D'Elia AV, Tell G, Arturi F, Russo D, Filetti S, Damante G (Feb 2004). "Functional interaction among thyroid-specific transcription factors: Pax8 regulates the activity of Hex promoter". Molecular and Cellular Endocrinology214 (1-2): 117–25. doi:10.1016/j.mce.2003.10.061. PMID15062550.
Swingler TE, Bess KL, Yao J, Stifani S, Jayaraman PS (Aug 2004). "The proline-rich homeodomain protein recruits members of the Groucho/Transducin-like enhancer of split protein family to co-repress transcription in hematopoietic cells". The Journal of Biological Chemistry279 (33): 34938–47. doi:10.1074/jbc.M404488200. PMID15187083.