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Human ARX gene: genomic characterization and expression.
1Department of Human Genetics, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095-1752, USA.
Molecular Genetics and Metabolism
|October 3, 2002
Summary
The human ARX gene is crucial for neuronal development, with expression patterns in fetal brain suggesting roles in differentiating specific brain cells. Studies in model organisms offer insights into ARX
Area of Science:
- Developmental Neuroscience
- Human Genetics
- Gene Expression Analysis
Background:
- The homeobox-containing gene Arx shows high sequence similarity between mouse and zebrafish.
- Arx is expressed in the developing central nervous systems of vertebrates, including the forebrain and floor plate.
- Previous research indicated Arx's presence in the presumptive cortex of fetal mice.
Purpose of the Study:
- To identify genes within human chromosome Xp22.1-p21.3 involved in human neuronal development.
- To characterize the expression pattern of the human ARX gene in the developing central nervous system.
- To establish the orthologous relationship between human ARX and murine Arx.
Main Methods:
- In silico analysis of a human Xp22 PAC sequence (RPCI1-258N20) to identify putative ARX exons.
- Northern blot analysis to determine human ARX transcript size and tissue expression.
- In situ hybridization on human fetal brain sections to localize ARX expression during development.
- Radiation hybrid mapping to localize the murine Arx gene.
Main Results:
- A 3.3kb human ARX transcript was highly expressed in fetal brain.
- A 5.9kb transcript showed expression in adult heart, skeletal muscle, and liver, with faint brain expression.
- In situ hybridization revealed highest ARX expression in neuronal precursors within the ganglionic eminence and telencephalon's ventricular zone.
- ARX expression was also detected in the hippocampus, cingulate cortex, subventricular zone, cortical plate, caudate nucleus, and putamen.
- Murine Arx was mapped, confirming Arx and ARX as orthologues.
Conclusions:
- The expression pattern of human ARX suggests its involvement in the differentiation and maintenance of specific neuronal cell types in the human central nervous system.
- Studies in model vertebrates like mice and zebrafish can provide valuable insights into ARX's developmental roles.
- The identification of ARX mutations in patients with mental retardation underscores the importance of studying this gene in model organisms.