| RAX | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Aliases | RAX , MCOP3, RX, retina and anterior neural fold homeobox | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 601881 MGI: 109632 HomoloGene: 8383 GeneCards: RAX | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Retinal homeobox protein Rx also known as retina and anterior neural fold homeobox is a protein that in humans is encoded by the RAX gene. [5] The RAX gene is located on chromosome 18 in humans, mice, and rats. [6]
This gene encodes a homeobox-containing transcription factor that functions in eye development. The gene is expressed early in the eye primordia, and is required for retinal cell fate determination and also regulates stem cell proliferation. [5]
Towards the end of late gastrulation a single eye field has formed and splits into bilateral fields via action by the signaling molecule, sonic hedgehog (Shh) secreted from the forebrain. Rax and Six-3 (also a transcription factor) maintain the forebrain's ability to secrete Shh by inhibiting activity of the signaling molecule Wnt. [7]
Rax (Retina and Anterior Neural Fold Homeobox) is a gene in the OAR (Otx, Arx,& Rax) subgroup of the paired-like homeodomain family of transcription factors. Discovered in 1997, [8] the Rax gene is known to contribute to the development of the retina, hypothalamus, pineal gland and pituitary gland. [9]
Mutations in this gene have been reported in patients with defects in ocular development, including microphthalmia, anophthalmia, and coloboma. [5]
Mutations to the Rax gene cause malformation of the retinal field, including anophthalmia and microphthalmia. [10]
Individuals who have a mutation in the RAX gene fail to develop ocular structures, referred to as anophthalmia. [7] RAX mutant individuals can also have microphthalmia, where one or both of the eyes is smaller than normal. [6]
Rax genes are conserved among vertebrates. RAX knockout mice have no eyes and abnormal forebrain formation. In the frog Xenopus tropicalis , Rax mutants are eyeless; the future retinal tissue instead has diencephalon and telencephalon features. [11] Due to a genome duplication at the basis of the teleost fish lineage, fishes contain three Rax genes: Rx1, Rx2, and Rx3. [12] Zebrafish and medaka mutants in Rx3 are eyeless. [12] [13]
In the developing chordate, the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural fold become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into the closed neural tube. In humans, neural tube closure usually occurs by the fourth week of pregnancy.
Sonic hedgehog protein (SHH) is encoded for by the SHH gene. The protein is named after the character Sonic the Hedgehog.
Microphthalmia, also referred as microphthalmos, is a developmental disorder of the eye in which one or both eyes are abnormally small and have anatomic malformations. Microphthalmia is a distinct condition from anophthalmia and nanophthalmia. Although sometimes referred to as 'simple microphthalmia', nanophthalmia is a condition in which the size of the eye is small but no anatomical alterations are present.
Paired box protein Pax-6, also known as aniridia type II protein (AN2) or oculorhombin, is a protein that in humans is encoded by the PAX6 gene.
Anophthalmia is the medical term for the absence of one or both eyes. Both the globe and the ocular tissue are missing from the orbit. The absence of the eye will cause a small bony orbit, a constricted mucosal socket, short eyelids, reduced palpebral fissure and malar prominence. Genetic mutations, chromosomal abnormalities, and prenatal environment can all cause anophthalmia. Anophthalmia is an extremely rare disease and is mostly rooted in genetic abnormalities. It can also be associated with other syndromes.
Eye formation in the human embryo begins at approximately three weeks into embryonic development and continues through the tenth week. Cells from both the mesodermal and the ectodermal tissues contribute to the formation of the eye. Specifically, the eye is derived from the neuroepithelium, surface ectoderm, and the extracellular mesenchyme which consists of both the neural crest and mesoderm.
Homeobox expressed in ES cells 1, also known as homeobox protein ANF, is a homeobox protein that in humans is encoded by the HESX1 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 OTX2 is a protein that in humans is encoded by the OTX2 gene.
Homeobox protein SIX3 is a protein that in humans is encoded by the SIX3 gene.
Visual system homeobox 1 is a protein that in humans is encoded by the VSX1 gene.
Visual system homeobox 2 is a protein that in humans is encoded by the VSX2 gene.
Homeobox protein Nkx-2.2 is a protein that in humans is encoded by the NKX2-2 gene.
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.
Cell adhesion molecule-related/down-regulated by oncogenes is a protein that in humans is encoded by the CDON gene.
Ventral anterior homeobox 1 is a protein that in humans is encoded by the VAX1 gene.
Homeobox protein DBX2, also known as developing brain homeobox protein 2, is a protein that in humans is encoded by the DBX2 gene. DBX2 plays an important role in the development of the central nervous system, specifically in the development of the neural tube and brain. DBX2 is located on chromosome 12 and is approximately 36,000 base pairs long. DBX2 is predicted to enable DNA-binding transcription activity as well as being involved in the regulation of transcription by RNA polymerase II.
Teneurin-3, also known as Ten-m3, Odz3, Ten-m/Odz3, Tenascin-like molecule major 3 or Teneurin transmembrane protein 3, is a protein that, in humans, is encoded by the TENM3, or ODZ3, gene. Ten-m3 is a ~300 kDa type II transmembrane glycoprotein that is a member of the teneurin/Ten-m/Odz family. The teneurin family currently consists of four members: Ten-m1-Ten-m4. Ten-ms are conserved across both vertebrate and invertebrate species. They are expressed in distinct, but often interconnected, areas of the developing nervous system and in some non-neural tissues. Like the Ten-m family, Ten-m3 plays a critical role in regulating connectivity of the nervous system, particularly in axon pathfinding and synaptic organisation in the motor and visual system. Mutation in the TENM3/ODZ3 gene in humans has been associated with the eye condition, microphthalmia.
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.
Makoto Furutani-Seiki is a Japanese molecular biologist who is a Professor of Systems Biochemistry in the School of Medicine at Yamaguchi University, Japan.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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