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Tbx22

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Tbx22

T-box 22
Identifiers
Symbols  ; ABERS; CLPA; CPX; TBXX; dJ795G23.1
External IDs GeneCards:
Orthologs
Species Human Mouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)
RefSeq (protein)
Location (UCSC)
PubMed search

T-box transcription factor TBX22 is a protein that in humans is encoded by the TBX22 gene.[1]

TBX22 is a member of a phylogenetically conserved family of proteins that share a common DNA-binding domain, the T-box. T-box genes encode transcription factors involved in the regulation of developmental processes. Mutations in this gene have been associated with the inherited X-linked disorder, cleft palate with ankyloglossia (tongue-tie), and it is believed to play a major role in human palatogenesis.[1]It has previously been mapped to the long arm of the X chromosome and it has now been demonstrated that mutations in the gene TBX22 are the cause of this syndrome.[2] TBX22 mutations also result in non-syndromic cleft palate in some populations. [3]

TBX22 is composed of seven exons spanning 8.7 kilobases of genomic DNA in Xq21.1. The TBX22 mRNA is 2099 base pairs long and encodes a 400-amino-acids protein containing a T-domain in its NH2-terminal region which has the unique feature of missing 20 amino-acids relative to the other known T-domains.[4]

Function

T-box genes are members of a family of transcriptional regulators that contain a region encoding a conserved DNA-binding motif of approximately 200 amino acids: the T-domain. These genes are grouped together on the basis of the homology existing between their products and the mouse Brachyury (or T) protein. In human and mouse, numerous T-domain-containing genes have been identified so far and mapped throughout the genome. The spatio-temporal expression of these genes is strictly regulated during the development of both vertebrates and invertebrates.[4]

Functional studies have demonstrated that several T-box genes are involved in Drosophila or zebrafish.

Clinical significance

TBX22 mutations in two families predicted to have X linked cleft palate and ankyloglossia. Sequence electropherograms from genomic DNA amplified from exon 5 (family K) and exon 4 (family W) are of affected (mutant) males and unaffected (control) females. *Represents the site of the sequence variant.

In humans, two T-box genes are involved in inherited disorders: mutations in TBX5 cause Holt–Oram syndrome, whereas mutations in TBX3 cause ulnar–mammary syndrome.[4]

Mutations in TBX22 cause X-linked cleft palate and ankyloglossia.[5] CPX has been described in a small number of families exhibiting a strong X linked Mendelian inheritance. The cleft phenotype predominantly affects males who show variation ranging from a complete cleft of the secondary palate, submucous cleft, or bifid uvula to high arched palate. Ankyloglossia is frequently seen in affected patients and carrier females, and has proved to be a useful indicator of CPX. Temporal and spatial studies using in situ hybridization in both human and mouse has shown that TBX22/Tbx22 is expressed primarily in the palatal shelves and tongue during palatogenesis, indicating a specific role of TBX22 in both palatal and tongue development. In addition to families with well defined X linked inheritance, TBX22 mutations have been identified in several families where pedigree size and/or family history were too limited to predict mode of inheritance. In these cases, ascertainment was largely based on the presence of ankyloglossia as well as cleft palate.[6]

It has been demonstrated that TBX22 makes a significant contribution to the prevalence of cleft palate at least in the Brazilian and the North American cohorts. [4] To date, 10 different TBX22 mutations have been reported in patients with CP and/or ankyloglossia.[7] These include small deletions/insertions, nonsense, splice site, frameshift and missense alterations.[3]

References

  1. ^ a b
  2. ^
  3. ^ a b
  4. ^ a b c d
  5. ^
  6. ^
  7. ^ Online 'Mendelian Inheritance in Man' (OMIM) T-BOX 22; TBX22 -300307

Further reading

External links

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