evolutionary developmental biology Evolutionary developmental biology, informally known as evo-devo, is a field of biological research that compares the developmental biology, developmental processes of different organisms to infer how developmental processes evolution, evolved. ...

, Paired box (Pax) genes are a family of

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s coding for tissue specific

transcription factors In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fun ...

containing an N-terminal paired domain and usually a partial, or in the case of four family members (PAX3, PAX4, PAX6 and PAX7), a complete homeodomain to the C-terminus. An octapeptide as well as a Pro-Ser-Thr-rich C terminus may also be present. Pax

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s are important in early animal development for the specification of specific tissues, as well as during epimorphic limb regeneration in animals capable of such. The paired domain was initially described in 1987 as the "paired box" in the ''Drosophila'' protein paired (prd; ).

Groups

Within the mammalian family, there are four well defined groups of Pax genes. *Pax group 1 (Pax 1 and 9), *Pax group 2 (Pax 2, 5 and 8), *Pax group 3 (Pax 3 and 7) and *Pax group 4 (Pax 4 and 6). Two more families, Pox-neuro and Pax-α/β, exist in basal bilaterian species. Orthologous genes exist throughout the Metazoa, including extensive study of the ectopic expression in Drosophila using

murine The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. Members of this subfamily are called murines. In terms of species richness, this subfamily is larger than all mammal families excep ...

Pax6. The two rounds of whole-genome duplications in vertebrate evolution is responsible for the creation of as many as 4 paralogs for each Pax protein.

Members

* PAX1 has been identified in mice with the development of vertebrate and embryo segmentation, and some evidence this is also true in humans. It transcribes a 440

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

protein from 4

exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence ...

s and 1,323 in humans. In the mouse Pax1 mutation has been linked to undulated mutant suffering from skeletal malformations. * PAX2 has been identified with

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

and optic nerve development. It transcribes a 417 amino acid protein from 11 exons and 4,261 in humans. Mutation of PAX2 in humans has been associated with renal-coloboma syndrome as well as oligomeganephronia. *

PAX3 The PAX3 (paired box gene 3) gene encodes a member of the paired box or Pax genes, 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 PAX ...

has been identified with ear, eye and facial development. It transcribes a 479 amino acid protein in humans. Mutations in it can cause

Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or Heterochromia iridum, one blue eye and one brown ey ...

is frequently expressed in

melanoma Melanoma is the most dangerous type of skin cancer; it develops from the melanin-producing cells known as melanocytes. It typically occurs in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In very rare case ...

s and contributes to tumor cell survival. * PAX4 has been identified with pancreatic islet beta cells. It transcribes a 350 amino acid protein from 9 exons and 2,010 in humans. Knockout mice lacking Pax4 expression fail to develop insulin-producing cells. Pax4 undergoes mutual reciprocal interaction with the transcription factor Arx to endow pancreatic endocrine cells with insulin and glucagon cells respectively * PAX5 has been identified with neural and spermatogenesis development and b-cell differentiation. It transcribes a 391 amino acid protein from 10 exons and 3,644 in humans. * PAX6 (eyeless) is the most researched and appears throughout the literature as a "master control" gene for the development of eyes and sensory organs, certain neural and epidermal tissues as well as other homologous structures, usually derived from

ectoderm The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...

al tissues. *

PAX7 Paired box protein Pax-7 is a protein that in humans is encoded by the ''PAX7'' gene. Function Pax-7 plays a role in neural crest development and gastrulation, and it is an important factor in the expression of neural crest markers such as Slu ...

has been possibly associated with

myogenesis Myogenesis is the formation of skeletal muscle, skeletal muscular tissue, particularly during embryonic development. Skeletal muscle#Skeletal muscle cells, Muscle fibers generally form through the fusion of precursor cell, precursor myoblasts in ...

. It transcribes a protein of 520 amino acids from 8 exons and 2,260 in humans. PAX7 directs postnatal renewal and propagation of myogenic satellite cells but not for the specification. * PAX8 has been associated with

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

specific expression. It transcribes a protein of 451 amino acids from 11 exons and 2,526 in humans. Pax8 loss-of-function mutant mice lack follicular cells of the thyroid gland. *

PAX9 Paired box gene 9, also known as PAX9, is a protein which in humans is encoded by the ''PAX9'' gene. It is also found in other mammals. Expression and function This gene is a member of the paired box (PAX) family of transcription factors. D ...

has found to be associated with a number of organ and other skeletal developments, particularly teeth. It transcribes a protein of 341 amino acids from 4 exons and 1,644 in humans.

References

Mansouri A et al. 1996

External links

A Review of the Highly Conserved PAX6 Gene in Eye Development Regulation

Paired domain
in PROSITE * {{InterPro content, IPR001523 Developmental genes and proteins Transcription factors

Groups

Members

See also

References

External links