Biology:TBX5 (gene)

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Short description: Protein-coding gene that affects limb development and heart and bone function


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

T-box transcription factor TBX5, (T-box protein 5) is a protein that in humans is encoded by the TBX5 gene.[1][2][3] Abnormalities in the TBX5 gene can result in altered limb development, Holt-Oram syndrome, Tetra-amelia syndrome, and cardiac and skeletal problems.

This gene is a member of a phylogenetically conserved family of genes that share a common DNA-binding domain, the T-box. T-box genes encode transcription factors involved in the regulation of developmental processes. This gene is closely linked[clarification needed] to related family member T-box 3 (ulnar mammary syndrome) on human chromosome 12.

TBX5 is located on the long arm of chromosome 12.[4] TBX5 produces a protein called T-box protein 5 that acts as a transcription factor.[5] TBX5 is involved with forelimb and heart development.[6] This gene impacts the early development of the forelimb by triggering fibroblast growth factor, FGF10.[7]

Function

TBX5 is a transcription factor that codes for the protein called T-box 5. The transcription factors it encodes are necessary for development, especially in the pattern formation of upper limbs and cardiac growth.[8] TBX5 is involved with the development of the four heart chambers, the electrical conducting system, and the septum separating the right and left sides of the heart.[9] Along with playing roles in the development of the heart, septum, and electrical system of the heart, it also activates genes that are involved in the development of the upper limbs, the arms and hands.

This gene is also involved in the muscle connective tissue for muscle and tendon patterning. A study showed that deletion of TBX5 in forelimbs causes disruption in the muscle and tendon patterning without affecting the skeleton's development.[10] T-box protein 5 expression is in the cells of the lateral plate mesoderm which form the forelimb bud and the cascade of limb initiation. In its absence, no forelimb bud forms.

The encoded protein plays a major role in limb development, specifically during limb bud initiation.[11] For instance, in chickens Tbx5 specifies forelimb status.[12] The activation of Tbx5 and other T-box proteins by Hox genes activates signaling cascades that involve the Wnt signaling pathway and FGF signals in limb buds.[11] Ultimately, Tbx5 leads to the development of apical ectodermal ridge (AER) and zone of polarizing activity (ZPA) signaling centers in the developing limb bud, which specify the orientation growth of the developing limb.[11] Together with Tbx4, Tbx5 plays a role in patterning the soft tissues (muscles and tendons) of the musculoskeletal system.[13]

As a protein-coding gene, TBX5 encodes for the protein T-box Transcription Factor 5, which is a part of the T-box family of transcription factors. It also interacts with other genes, such as GATA4 and NKX2-5, and the BAF chromatin-remodeling complex to drive and repress gene expression during development.[14]

Role in non-human animals

Mice that were genetically modified to not have the TBX5 gene did not survive gestation, due to the heart not developing past embryonic day E10.5. Mice that only had one working copy of TBX5 were born with morphological problems such as enlarged hearts, atrial and ventral septum defects, and limb malformations similar to those found in the Holt-Oram Syndrome.[15]

Pigeons with feathered feet have Tbx5 active in the hind feet, which cause them to develop feathered hindlimbs with thicker bones, more similar to their frontlimb wings.[16][17]

Role in human embyronic development

A gene "knockout" model for TBX5 by CRISPR/Cas9 genome editing has been created.[18] This homozygous TBX5 knockout human embryonic stem cell line, called TBX5-KO maintained stem cell-like morphology, pluripotency markers, normal karyotype, and could differentiate into all three germ layers in vivo. This cell line can provide an in vitro platform for studying the pathogenic mechanisms and biological function of TBX5 in the heart development.[18] By understanding what happens in development without this gene, further treatment options for fetuses with a TBX5 mutation might be possible to prevent the severe cardiac defects associated with Holt-Oram Syndrome.

Clinical significance

Mutations in this gene can result in Holt–Oram syndrome, a developmental disorder affecting the heart and upper limbs.[19][6] Holt-Oram syndrome can cause a hole in the septum,[5] bone abnormalities in the fingers, wrists, or arms,[20] and a conduction disease leading to abnormal heart rates and arrhythmias.[4] The most common cardiac issue associated with this condition is the malformation of the septum, which separates the left and right sides of the heart.[21]

Tetra-amelia syndrome is a condition where forelimb malformation occurs because FGF-10 is not triggered due to Tbx5 mutations.[22] This condition can lead to the absence of one or both forelimbs.

Skeletally, there may be abnormally bent fingers, sloping shoulders, and phocomelia. Cardiac defects include ventral and atrial septation and problems with the conduction system.[23] Several transcript variants encoding different isoforms have been described for this gene.[3]

Interactions

TBX5 (gene) has been shown to interact with:

References

  1. ↑ "Mutations in human TBX5 [corrected] cause limb and cardiac malformation in Holt-Oram syndrome". Nature Genetics 15 (1): 30–35. January 1997. doi:10.1038/ng0197-30. PMID 8988165. 
  2. ↑ "Holt-Oram syndrome is a genetically heterogeneous disease with one locus mapping to human chromosome 12q". Nature Genetics 6 (4): 401–404. April 1994. doi:10.1038/ng0494-401. PMID 8054982. 
  3. ↑ 3.0 3.1 "Entrez Gene: TBX5 T-box 5". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=6910. 
  4. ↑ 4.0 4.1 "TBX5 intragenic duplication: a family with an atypical Holt-Oram syndrome phenotype". European Journal of Human Genetics 20 (8): 863–869. August 2012. doi:10.1038/ejhg.2012.16. PMID 22333898. 
  5. ↑ 5.0 5.1 "Clinical and molecular characterisation of Holt-Oram syndrome focusing on cardiac manifestations". Cardiology in the Young 25 (6): 1093–1098. August 2015. doi:10.1017/s1047951114001656. PMID 25216260. 
  6. ↑ 6.0 6.1 "TBX5: A Key Regulator of Heart Development". Current Topics in Developmental Biology 122: 195–221. 2017. doi:10.1016/bs.ctdb.2016.08.008. PMID 28057264. 
  7. ↑ "RA Acts in a Coherent Feed-Forward Mechanism with Tbx5 to Control Limb Bud Induction and Initiation". Cell Reports 12 (5): 879–891. August 2015. doi:10.1016/j.celrep.2015.06.068. PMID 26212321. 
  8. ↑ "TBX5 t-Box Transcription Factor 5 [Homo Sapiens (Human) - Gene - NCBI.""]. National Center for Biotechnology Information. U.S. National Library of Medicine. https://www.ncbi.nlm.nih.gov/gene/6910. 
  9. ↑ "TBX5 and NuRD Divide the Heart". Developmental Cell 36 (3): 242–244. February 2016. doi:10.1016/j.devcel.2016.01.015. PMID 26859347. 
  10. ↑ "Tbx4 and tbx5 acting in connective tissue are required for limb muscle and tendon patterning". Developmental Cell 18 (1): 148–156. January 2010. doi:10.1016/j.devcel.2009.11.013. PMID 20152185. 
  11. ↑ 11.0 11.1 11.2 "How the embryo makes a limb: determination, polarity and identity". Journal of Anatomy 227 (4): 418–430. October 2015. doi:10.1111/joa.12361. PMID 26249743. 
  12. ↑ "The T-box genes Tbx4 and Tbx5 regulate limb outgrowth and identity". Nature 398 (6730): 814–818. April 1999. doi:10.1038/19769. PMID 10235264. Bibcode: 1999Natur.398..814R. 
  13. ↑ "Tbx4 and tbx5 acting in connective tissue are required for limb muscle and tendon patterning". Developmental Cell 18 (1): 148–156. January 2010. doi:10.1016/j.devcel.2009.11.013. PMID 20152185. 
  14. ↑ "TBX5: A Key Regulator of Heart Development". Current Topics in Developmental Biology 122: 195–221. 2017. doi:10.1016/bs.ctdb.2016.08.008. PMID 28057264. 
  15. ↑ "Tbx5 specifies the left/right ventricles and ventricular septum position during cardiogenesis". Development 130 (24): 5953–5964. December 2003. doi:10.1242/dev.00797. PMID 14573514. 
  16. ↑ "Pigeon foot feathering reveals conserved limb identity networks". Developmental Biology 454 (2): 128–144. October 2019. doi:10.1016/j.ydbio.2019.06.015. PMID 31247188. 
  17. ↑ "Pigeon foot feather genes identified | UNews" (in en-US). https://unews.utah.edu/pigeon-foot-feather-genes-identified/. 
  18. ↑ 18.0 18.1 "Generation of a TBX5 homozygous knockout embryonic stem cell line (WAe009-A-45) by CRISPR/Cas9 genome editing". Stem Cell Research 51: 102156. March 2021. doi:10.1016/j.scr.2021.102156. PMID 33497883. 
  19. ↑ "Holt Oram syndrome: a case report and review of the literature". Clinical and Experimental Obstetrics & Gynecology 43 (1): 137–139. 2016. doi:10.12891/ceog3060.2016. PMID 27048037. 
  20. ↑ "Connexin 40, a target of transcription factor Tbx5, patterns wrist, digits, and sternum". Molecular and Cellular Biology 25 (12): 5073–5083. June 2005. doi:10.1128/mcb.25.12.5073-5083.2005. PMID 15923624. 
  21. ↑ "Holt-Oram Syndrome". Medlineplus Genetics. U.S. National Library of Medicine. 18 August 2020. https://medlineplus.gov/genetics/condition/holt-oram-syndrome/#causes.. 
  22. ↑ "Tetra-Amelia Syndrome – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY", Tetra-Amelia Syndrome, GeneReviews, University of Washington, Seattle, 1993, PMID 20301453, http://www.ncbi.nlm.nih.gov/books/NBK1276/ 
  23. ↑ "T-box genes in human disorders". Human Molecular Genetics 12 Spec No 1 (Spec No 1): R37–R44. April 2003. doi:10.1093/hmg/ddg077. PMID 12668595. 
  24. ↑ 24.0 24.1 "GATA4 mutations cause human congenital heart defects and reveal an interaction with TBX5". Nature 424 (6947): 443–447. July 2003. doi:10.1038/nature01827. PMID 12845333. Bibcode: 2003Natur.424..443G. 
  25. ↑ "Tbx5 associates with Nkx2-5 and synergistically promotes cardiomyocyte differentiation". Nature Genetics 28 (3): 276–280. July 2001. doi:10.1038/90123. PMID 11431700. 

Further reading

External links



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