Developmental Signals - Pax

Embryology - 16 Apr 2024        Expand to Translate
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Introduction

Phylogenetic tree of Pax genes

The name derived from Drosophila gene "paired" (prd) with a box (homeodomain) domain. A transcription factor of the helix-turn-helix structural family, DNA binding, and activating gene expression. In human, there are nine member proteins from Pax1 to Pax9.

Pax6 has been identified as regulating development of the central nervous system, eyes, nose, pancreas and pituitary gland.

Developmental Functions: Mesoderm | Neural | Vision | Pancreas | Pituitary | Thymus

Some Recent Findings

Review - Pax genes: regulators of lineage specification and progenitor cell maintenance "Pax genes encode a family of transcription factors that orchestrate complex processes of lineage determination in the developing embryo. Their key role is to specify and maintain progenitor cells through use of complex molecular mechanisms such as alternate RNA splice forms and gene activation or inhibition in conjunction with protein co-factors. The significance of Pax genes in development is highlighted by abnormalities that arise from the expression of mutant Pax genes. Here, we review the molecular functions of Pax genes during development and detail the regulatory mechanisms by which they specify and maintain progenitor cells across various tissue lineages." Downstream genes of Pax6 in the developing rat hindbrain "These results indicate that Unc5h1 and Cyp26b1 are novel candidates for target genes transactivated by Pax6. Furthermore, our results suggest the interesting possibility that Pax6 regulates anterior-posterior patterning of the hindbrain via activation of Cyp26b1, an enzyme that metabolizes retinoic acid."

More recent papers

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Development Pax <pubmed limit=5>Development Pax</pubmed>

Transcription Factor

Pax and DNA molecular interaction

Mesoderm Development

Mesoderm Development and Pax

Neural Development

Mouse- early Pax8 and Pax2 expression

• Hoxd4 gene a direct target of Pax6
  • mouse embryo - Hoxd4 expression in rhombomere 7 and the spinal cord is reduced to some extent in the Pax6 mutant
  • zebrafish embryo - double knockdown of pax6a and pax6b with MOs resulted in malformed rhombomere boundaries and an anteriorized hoxd4a expression border

• Pax3 is expressed in the somite, neural tube, and neural crest.
• Pax3 is required for enteric ganglia formation.
• Pax2 and Pax5 in midbrain and cerebellum development.

Vision Development

Pax6 mutation eye phenotypes

Pancreas Development

• Pax6 acts in endocrine development in the pancreas as a glucagon gene transactivator role in alpha (α) cell development.
• Pax2 is also expressed in the pancreas.
• Pax4 is a regulator of pancreatic beta cell development.

Developmental Factors

Pdx1 - Pancreas/Duodenum Homeobox Protein 1 OMIM 600733 transcription (transactivator) factor binds the TAAT element in the promoter region of target genes, mainly those involved in pancreas development. Ngn3 - Neurogenin3 OMIM 604882 basic helix-loop-helix transcription factor involved in the determination of neural precursor cells in the neuroectoderm. NeuroD1 - Neurogenic Differentiation 1 OMIM 601724 a basic helix-loop-helix (bHLH) protein that acts as a transcription factors involved in determining cell type during development. Arx - Aristaless-Related Homeobox, X-Linked OMIM 300382 homeobox protein that belongs to the Aristaless-related subset of the paired (Prd) class of homeodomain proteins. Pax4 - Paired Box Gene 4 OMIM 167413 transcription factor containing a paired box domain. Pax6 Paired Box Gene 6 OMIM 607108 transcription factor containing a paired box domain. Nkx2.2 - NK2 Homeobox 2 OMIM 604612 homeobox (Hox) containing transcription factor contain a 60-amino acid evolutionarily conserved DNA-binding homeodomain. Nkx6.1 - NK2 Homeobox 6.1 OMIM 602563 homeobox (Hox) containing transcription factor contain a 60-amino acid evolutionarily conserved DNA-binding homeodomain. required for beta cells development and is completely conserved between rat, mouse, and human.

Molecular Development of Endocrine Pancreas Cells

Links: Endocrine Pancreas

Thymus Development

Pax1 mouse KO thymus size reduction and impaired thymocyte maturation.

Links: Thymus Pancreas

Structure

• tissue-specific transcriptional regulators
• contain a highly conserved DNA-binding domain with six alpha-helices (paired domain)
• a complete or residual homeodomain.
• 4 Groups: group I (Pax-1, 9), II (Pax-2, 5, 8), III (Pax-3, 7), and IV (Pax-4, 6)

Mouse Expression

The following gallery is from a recent paper using a Pax7-cre/reporter mouse.

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  E7.5 E8.5 neural fold

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  E9.5 Pax7 heart

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  E11.5 Trunk neural crest 1

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  E11.5 Trunk neural crest 2

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  E15.5 Pax7 limb

Mouse Palatal Shelf Wnt5a, Osr2 and Pax9 Expression.

The following data is from a recent paper using a Pax9 reporter.

Mouse Tongue Pax9 Expression in Different Taste Papillae
	E13.5 Mouse Tongue Pax9 Expression in Different Taste Papillae A. Drawing showing the localization of the circumvallate papilla (CVP), foliate papillae (FOP), and fungiform papillae (FUP) in the mouse tongue. B. Whole mount X-Gal staining of a Pax9+/LacZ mouse tongue at embryonic day 13.5 (E13.5). Note that expression is also seen in the mesenchyme adjacent to the developing FOP (arrowheads) and that the color reaction was stopped before epithelial staining began to obscure the mesenchymal expression domain. B Scale bar 200 µm.
	E13.5 -E18.5 Mouse Tongue Pax9 Expression in Different Taste Papillae Pax9 immunostaining of taste papillae during development on cross sections (C–F; K–N) and horizontal sections of the tongue (G–J). C–F Pax9 is expressed in the epithelium during CVP morphogenesis and is down-regulated in some regions of the trenches at E18.5 (arrowhead in F). G–J In addition to the epithelium, Pax9 is also expressed in the mesenchyme during FOP development, while reduced Pax9 levels were observed in the trenches at E18.5 (arrowhead in J). K–N In the anterior part of the tongue Pax9 is expressed in the FUP epithelium and in filiform papillae (FIP). Note that the expression is very weak or absent in the taste placodes (arrowheads). Scale bars 50 µm.

Links: Mouse Development | Neural Crest Development | Taste Development

Abnormalities

Associated with defects in each Pax protein or their signaling pathway.

Pax2

• renal-coloboma syndrome (RCS)

Links: Vision Abnormalities | Genetics Home Reference

Pax3

• Waardenburg syndrome type 1 (WS1)
• Waardenburg syndrome type 3 (WS3)
• craniofacial-deafness-hand syndrome (CDHS)
• rhabdomyosarcoma type 2 (RMS2)

Pax5

• acute lymphoblastic leukemia

Pax6

A series of vision associated defects.

• aniridia (AN)
• Peters anomaly
• ectopia pupillae
• foveal hypoplasia
• autosomal dominant keratitis
• ocular coloboma
• coloboma of optic nerve
• bilateral optic nerve hypoplasia
• aniridia cerebellar ataxia and mental deficiency (ACAMD)

Links: Vision Abnormalities

Pax7

• rhabdomyosarcoma type 2 (RMS2)

Pax8

• congenital hypothyroidism non-goitrous type 2 (CHNG2)

Links:Thyroid Abnormalities

References

Search Bookshelf Pax

Reviews

<pubmed>17506689</pubmed> <pubmed>10197584</pubmed>

Search Pubmed

Search Pubmed Now: Pax

http://www.ncbi.nlm.nih.gov/omim

External Links

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• OMIM - Pax6

Glossary Links

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Cite this page: Hill, M.A. (2024, April 16) Embryology Developmental Signals - Pax. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Developmental_Signals_-_Pax

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G