GBX2

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GBX2
Identifiers
Gene ontology
Molecular function
Cellular component
Biological process
Sources:Amigo / QuickGO
Ensembl

ENSG00000168505

ENSMUSG00000034486

UniProt

P52951

P48031

RefSeq (mRNA)

NM_001485
NM_001301687

NM_010262

RefSeq (protein)

NP_001288616
NP_001476

NP_034392

Location (UCSC)Chr 2: 236.17 – 236.17 MbChr 1: 89.86 – 89.86 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Homeobox protein GBX-2 is a protein that in humans is encoded by the GBX2 gene.[5][6][7]

Summary

Gastrulation Brain Homeobox 2, or commonly known as GBX2, is a type of transcription factor that aids in the arranging of the midbrain and hindbrain during gastrulation. The hindbrain is broken up into seven or eight rhombomeres during gastrulation and GBX2 is responsible for rhombomeres one through three. GBX2 also takes part in the signaling and expression of other genes. It has been said that there is a threshold requirement for the amount of GBX2, so what occurs depends on the amount expressed. For example, specific amounts of GBX2 is needed for regulating the anterior and posterior patterning in the hindbrain. If the specific threshold is not met, then the patterning does not occur. This is the case with the other genes it helps to express like FGF8. With every gene comes some diseases associated with it. Colon Small Cell Carcinoma and Optiz-Gbbb Syndrome, which causes abnormalities throughout the midline of the body, are the diseases most closely associated with the GBX2 gene. [8]

Function

Gastrulation Brain Homeobox 2 (GBX2) is a

FGF8
. Since this is a dosage dependent gene, the different amounts of gene present in certain location can cause different outcomes. FGF8 is affected by the different dosages in the location it is expressed. The absence of GBX2 causes FGF8 expression is shifted caudally and over expression of GBX2 causes FGF8 expression to be shifted rostrally. Not all of the rhombomeres GBX2 is expressed in require the same strictness of dose regulation. Of the three, rhombomere 2 has the most strict dose requirements.

Neural Crest Cell Development

The Gbx-2 gene is thought to be involved in

embryonic ectoderm differentiates into these neural crest cells, which give rise to many structures including muscle, neurons, and bone later in development. In order to test Gbx-2's role in neural crest cell development, the region of neural cell proliferation was injected with the morphogen Wnt8. In response, Snail2 was expressed, which led to transcription factor activation and subsequent protein formation. When Wnt8 was inhibited in the same region, no transcription factors were expressed and neural cell growth was inhibited or not seen. There have also been studies that showed that when the reverse occurred, with the absence or presence of Snail2 affecting Wnt8, similar effects to transcription factor activation occurred. Such research has shown that transcription factor activation is dependent on both genes. Wnt is thought to be a neural crest cell inducer, and Gbx-2 is one of the gene targets involved.[9]
In cases where Gbx-2 mRNA is in excess, an expansion of neural crest cells is seen, whereas when there is a lack of mRNA, neural crest cells fail to proliferate. If neural crest cells are unable to proliferate, many of the body's important organs and processes will be inhibited and could likely lead to miscarriage of the fetus.


Animal studies

Knockout of the GBX2 gene causes the failure of many structures to form, such as the isthmic nuclei, the cerebellum, motor nerve V and many other derivatives of rhombomeres 1-3. GBX2 gene knockout embryos will continue to develop and will reach full term pregnancy. The babies are born but if there is a lack of GBX2 expression all will die soon after birth.[10][11]

Knockdown of the gbx2 gene leads to a truncated anterior hindbrain as well as abnormal clusters of cell bodies in r2 and r3 which are associated with problems in cranial nerve V. It has been shown that any structures derived from r1-r3 will be adversely affected by mutations or deficiencies in gbx2. These structures include the aortic arch and right Subclavian artery which, when improperly developed, can lead to cardiovascular defects in addition to craniofacial defects from improper development of cranial nerve V.[12]

References

  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000168505 – Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000034486 – Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. S2CID 15954797
    .
  6. PMID 8838315
    .
  7. ^ "Entrez Gene: GBX2 gastrulation brain homeobox 2".
  8. ^ Waters, S. T. “A Threshold Requirement for Gbx2 Levels in Hindbrain Development.” Development, vol. 133, no. 10, 2006, pp. 1991–2000., doi:10.1242/dev.02364.
  9. PMID 19736322
    .
  10. PMID 9247335
    .
  11. S2CID 1080009
    .
  12. PMID 23933069
    .

Further reading


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