Paired box gene 2, also known as Pax-2, is a protein which in humans is encoded by the PAX2 gene. [5] [6]
Paired box gene 2, also known as Pax-2, is a protein which in humans is encoded by the PAX2 gene. [5] [6]
The Pax Genes, or Paired-Box Containing Genes, play important roles in the development and proliferation of multiple cell lines, development of organs, and development and organization of the central nervous system. [7] The transcription factor gene PAX2 is important in the regionalized embryological development of the central nervous system. In mammals, the brain is developed in three regions: the forebrain, midbrain, and the hindbrain. [8] Concentration gradients of fibroblast growth factor 8 (FGF8) and Wingless-Type MMTV Integration Site Family, Member 1 (Wnt1) control expression of Pax-2 during development of the Mesencephalon, or midbrain. [9] Similar patterning during embryological development can be observed in “basal chordates or ascidians,” in which organization of the central nervous system in ascidian larvae are also controlled by fibroblast growth factor genes. [8] PAX2 encodes for the transcription factor which appears to be essential in the organization of the midbrain and hindbrain regions, and at the earliest can be detected on either side of the sulcus limitans, which separates motor and sensory nerve nuclei. [7] [10]
PAX2 encodes paired box gene 2, one of many human homologues of the Drosophila melanogaster gene prd. The central feature of this transcription factor gene family is the conserved DNA-binding paired box domain. PAX2 is believed to be a target of transcriptional suppression by the tumor suppressor gene WT1. Pax 2 is a transcription factor controlled by the signaling molecules Wnt1 and Fgf8. Pax2 along with other transcription factors Pax5, Pax8, En1, and En 2 are expressed across the Otx2-Gbx2 boundary in the mid-hindbrain region. These transcription factors work with the signaling molecules Wnt1 and Fgf8 to maintain the MHB organizer. The MHB controls midbrain and cerebellum development. Pax2 is the earliest known gene to be expressed across the Otx2-Gbx2 boundary. It is first expressed in the late primitive streak stage and is expressed in a narrow ring centered at the MHB during somitogenesis. Transgene expression of the mid-hindbrain and developing kidney is directed by Pax2. There are three distinct MHB-specific enhancers in the upstream region of Pax2. Expression at the MHB from the four-somite stage onwards is directed by the two late enhancers in the proximal and distal regions of Pax2. The early enhancer located in the intermediate region activates the mid-hindbrain region of late gastrula embryos. The activation of Pax2, Pax5, and Pax8 is a conserved feature of all vertebrates.
Pathologically, Pax2 has been demonstrated to activate hepatocyte growth factor (HGF) gene promoter, and both have been indicated as playing a role in human prostate cancers. [11]
Mutations within PAX2 have been shown to result in optic nerve colobomas and renal hypoplasia. Alternative splicing of this gene results in multiple transcript variants. [12] Pax2 and Pax8 are also necessary for the formation of the pronephros and subsequent kidney structures. Pax2 and Pax8 regulate the expression of Gata3. Without these genes mutations in the urogenital system arise.
Pax2 misexpression is frequently observed in proliferative disorders of the kidney. For example, Pax2 is highly expressed in polycystic kidney disease (PKD), Wilms' tumor (WT), and renal cell carcinoma (RCC). [13] Pax2 expression in these diseases appears fuel cell cycling, inhibit cell death, and confer resistance to chemotherapy. [13] Due to its role in these diseases, Pax2 is an attractive therapeutic target and a number of methods for inhibiting its activity have been investigated. In fact, a small-molecule was recently identified with the ability to disrupt Pax2 mediated transcription by blocking Pax2 from binding to DNA. [14] [15]
In the vertebrate embryo, a rhombomere is a transiently divided segment of the developing neural tube, within the hindbrain region in the area that will eventually become the rhombencephalon. The rhombomeres appear as a series of slightly constricted swellings in the neural tube, caudal to the cephalic flexure. In human embryonic development, the rhombomeres are present by day 29.
In evolutionary developmental biology, Paired box (Pax) genes are a family of genes coding for tissue specific transcription factors containing an N-terminal paired domain and usually a partial, or in the case of four family members, a complete homeodomain to the C-terminus. An octapeptide as well as a Pro-Ser-Thr-rich C terminus may also be present. Pax proteins are important in early animal development for the specification of specific tissues, as well as during epimorphic limb regeneration in animals capable of such.
Intermediate mesoderm or intermediate mesenchyme is a narrow section of the mesoderm located between the paraxial mesoderm and the lateral plate of the developing embryo. The intermediate mesoderm develops into vital parts of the urogenital system.
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.
The PAX3 gene encodes a member of the paired box or PAX family of transcription factors. The PAX family consists of nine human (PAX1-PAX9) and nine mouse (Pax1-Pax9) members arranged into four subfamilies. Human PAX3 and mouse Pax3 are present in a subfamily along with the highly homologous human PAX7 and mouse Pax7 genes. The human PAX3 gene is located in the 2q36.1 chromosomal region, and contains 10 exons within a 100 kb region.
Papillorenal syndrome is an autosomal dominant genetic disorder marked by underdevelopment (hypoplasia) of the kidney and colobomas of the optic nerve.
LIM homeobox transcription factor 1-beta, also known as LMX1B, is a protein which in humans is encoded by the LMX1B gene.
The nuclear receptor 4A2 (NR4A2) also known as nuclear receptor related 1 protein (NURR1) is a protein that in humans is encoded by the NR4A2 gene. NR4A2 is a member of the nuclear receptor family of intracellular transcription factors.
Early growth response protein 2 is a protein that in humans is encoded by the EGR2 gene. EGR2 is a transcription regulatory factor, containing three zinc finger DNA-binding sites, and is highly expressed in a population of migrating neural crest cells. It is later expressed in the neural crest derived cells of the cranial ganglion. The protein encoded by Krox20 contains two cys2his2-type zinc fingers. Krox20 gene expression is restricted to the early hindbrain development. It is evolutionarily conserved in vertebrates, humans, mice, chicks, and zebra fish. In addition, the amino acid sequence and most aspects of the embryonic gene pattern is conserved among vertebrates, further implicating its role in hindbrain development. When the Krox20 is deleted in mice, the protein coding ability of the Krox20 gene is diminished. These mice are unable to survive after birth and exhibit major hindbrain defects. These defects include but are not limited to defects in formation of cranial sensory ganglia, partial fusion of the trigeminal nerve (V) with the facial (VII) and auditory (VII) nerves, the proximal nerve roots coming off of these ganglia were disorganized and intertwined among one another as they entered the brainstem, and there was fusion of the glossopharyngeal (IX) nerve complex.
Paired box gene 8, also known as PAX8, is a protein which in humans is encoded by the PAX8 gene.
Paired-like homeodomain transcription factor 2 also known as pituitary homeobox 2 is a protein that in humans is encoded by the PITX2 gene.
Fibroblast growth factor 8(FGF-8) is a protein that in humans is encoded by the FGF8 gene.
Sal-like 1 (Drosophila), also known as SALL1, is a protein which in humans is encoded by the SALL1 gene. As the full name suggests, it is one of the human versions of the spalt (sal) gene known in Drosophila.
Sal-like protein 4(SALL4) is a transcription factor encoded by a member of the Spalt-like (SALL) gene family, SALL4. The SALL genes were identified based on their sequence homology to Spalt, which is a homeotic gene originally cloned in Drosophila melanogaster that is important for terminal trunk structure formation in embryogenesis and imaginal disc development in the larval stages. There are four human SALL proteins with structural homology and playing diverse roles in embryonic development, kidney function, and cancer. The SALL4 gene encodes at least three isoforms, termed A, B, and C, through alternative splicing, with the A and B forms being the most studied. SALL4 can alter gene expression changes through its interaction with many co-factors and epigenetic complexes. It is also known as a key embryonic stem cell (ESC) factor.
Transcription factor MafB also known as V-maf musculoaponeurotic fibrosarcoma oncogene homolog B is a protein that in humans is encoded by the MAFB gene. This gene maps to chromosome 20q11.2-q13.1, consists of a single exon and spans around 3 kb.
Protein odd-skipped-related 1 is a transcription factor that in humans is encoded by the OSR1 gene. The OSR1 and OSR2 transcription factors participate in the normal development of body parts such as the kidney.
Homeobox protein GBX-2 is a protein that in humans is encoded by the GBX2 gene.
Forkhead box protein E3 (FOXE3) also known as forkhead-related transcription factor 8 (FREAC-8) is a protein that in humans is encoded by the FOXE3 gene located on the short arm of chromosome 1.
Forkhead box protein J1 is a protein that in humans is encoded by the FOXJ1 gene. It is a member of the Forkhead/winged helix (FOX) family of transcription factors that is involved in ciliogenesis. FOXJ1 is expressed in ciliated cells of the lung, choroid plexus, reproductive tract, embryonic kidney and pre-somite embryo stage.
The isthmic organizer, or isthmus organizer, also known as the midbrain−hindbrain boundary (MHB), is a secondary organizer region that develops at the junction of the midbrain and metencephalon. The MHB expresses signaling molecules that regulate the differentiation and patterning of the adjacent neuroepithelium. This allows for the development of the midbrain and hindbrain as well as the specification of neuronal subtypes in these regions. The fact that the MHB is sufficient for the development of the mid and hindbrain was shown in an experiment where quail MHB cells transplanted into the forebrain of a chick were able to induce an ectopic midbrain and cerebellum.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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