Paired box gene 9, also known as PAX9, is a protein which in humans is encoded by the PAX9 gene. [5] [6] It is also found in other mammals. [7]
Paired box gene 9, also known as PAX9, is a protein which in humans is encoded by the PAX9 gene. [5] [6] It is also found in other mammals. [7]
This gene is a member of the paired box (PAX) family of transcription factors. During mouse embryogenesis Pax9 expression starts from embryonic day 8.5 and becomes more evident by E9.5; at this stage its expression is restricted to the pharyngeal endoderm. [8] [9] Later on, Pax9 is also expressed in the axial skeleton. [8] Pax9 is required for craniofacial, tooth and limb development, [7] [8] and may more generally involve development of stratified squamous epithelia as well as various organs and skeletal elements. [5] PAX9 plays a role in the absence of wisdom teeth in some human populations (possibly along with the less well studied AXIN2 and MSX1). [7]
This gene was found amplified in lung cancer. The amplification covers three tissue developmental genes - TTF1, NKX2-8, and PAX9. [10] It appears that certain lung cancer cells select for DNA copy number amplification and increased RNA/protein expression of these three coamplified genes for functional advantages.
Oligodontia is a genetic disorder caused by the mutation of the PAX9 gene. This disorder results in the congenital absence of 6 or more permanent teeth, with the exception of the third molar. [11] Also known as selective tooth agenesis (STHAG), it is the most common disorder in regard to human dentition, affecting a little less than one fourth of the population. [11] The gene PAX9 which can be found on chromosome 14 encodes a group of transcription factors that play an important role in early tooth development. [12] In humans, a frameshift mutation in the paired domain of PAX9 was discovered in those affected with oligodontia. [13] Multiple mechanisms are possible by which the mutation may arise. Recently, a study involving the missense mutation of a PAX9 gene suggests that the loss of function due to the absence DNA binding domain is a mechanism that causes oligodontia. [14] Those who express the PAX9 mutation and develop the disorder continue to have a normal life expectancy. Along with the mutation of the PAX9 gene, MSX1 gene mutations have also shown to affect dental development in fetuses. [14]
The MYH16 gene encodes a protein called myosin heavy chain 16, which is a muscle protein in mammals. At least in primates, it is a specialized muscle protein found only in the temporalis and masseter muscles of the jaw. Myosin heavy chain proteins are important in muscle contraction, and if they are missing, the muscles will be smaller. In non-human primates, MYH16 is functional and the animals have powerful jaw muscles. In humans, the MYH16 gene has a mutation that causes the protein not to function. Although the exact importance of this change in accounting for differences between humans and other apes is not yet clear, such a change may be related to increased brain size and finer control of the jaw, which facilitates speech. It is not clear how the MYH16 mutation relates to other changes to the jaw and skull in early human evolution.
Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.
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.
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.
Paired box gene 2, also known as Pax-2, is a protein which in humans is encoded by the PAX2 gene.
Homeobox protein MSX-1, is a protein that in humans is encoded by the MSX1 gene. MSX1 transcripts are not only found in thyrotrope-derived TSH cells, but also in the TtT97 thyrotropic tumor, which is a well differentiated hyperplastic tissue that produces both TSHß- and a-subunits and is responsive to thyroid hormone. MSX1 is also expressed in highly differentiated pituitary cells which until recently was thought to be expressed exclusively during embryogenesis. There is a highly conserved structural organization of the members of the MSX family of genes and their abundant expression at sites of inductive cell–cell interactions in the embryo suggest that they have a pivotal role during early development.
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.
Forkhead box protein L2 is a protein that in humans is encoded by the FOXL2 gene.
T-box transcription factor TBX5, is a protein that in humans is encoded by the TBX5 gene. Abnormalities in the TBX5 gene can result in altered limb development, Holt-Oram syndrome, Tetra-amelia syndrome, and cardiac and skeletal problems.
Paired box gene 4, also known as PAX4, is a protein which in humans is encoded by the PAX4 gene.
Homeobox protein Hox-A13 is a protein that in humans is encoded by the HOXA13 gene.
Axin-2, also known as axin-like protein (Axil), axis inhibition protein 2 (AXIN2), or conductin, is a protein that in humans is encoded by the AXIN2 gene.
Paired-like homeodomain 1 is a protein that in humans is encoded by the PITX1 gene.
Paired box protein Pax-1 is a protein that in humans is encoded by the PAX1 gene.
Pancreas transcription factor 1 subunit alpha is a protein that in humans is encoded by the PTF1A gene.
Forkhead box protein N1 is a protein that in humans is encoded by the FOXN1 gene.
Maxillary lateral incisor agenesis (MLIA) is lack of development (agenesis) of one or both of the maxillary lateral incisor teeth. In normal human dentition, this would be the second tooth on either side from the center of the top row of teeth. The condition is bilateral if the incisor is absent on both sides or unilateral if only one is missing. It appears to have a genetic component.
(HES7) or bHLHb37 is protein coding mammalian gene found on chromosome 17 in humans. HES7 is a member of the Hairy and Enhancer of Split families of Basic helix-loop-helix proteins. The gene product is a transcription factor and is expressed cyclically in the presomitic mesoderm as part of the Notch signalling pathway. HES7 is involved in the segmentation of somites from the presomitic mesoderm in vertebrates. The HES7 gene is self-regulated by a negative feedback loop in which the gene product can bind to its own promoter. This causes the gene to be expressed in an oscillatory manner. The HES7 protein also represses expression of Lunatic Fringe (LFNG) thereby both directly and indirectly regulating the Notch signalling pathway. Mutations in HES7 can result in deformities of the spine, ribs and heart. Spondylocostal dysostosis is a common disease caused by mutations in the HES7 gene. The inheritance pattern of Spondylocostal dysostosis is autosomal recessive.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.