Human Molecular Genetics Advance Access originally published online on July 15, 2009
Human Molecular Genetics 2009 18(19):3708-3724; doi:10.1093/hmg/ddp318
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Three human ARX mutations cause the lissencephaly-like and mental retardation with epilepsy-like pleiotropic phenotypes in mice
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1 Department of Mental Retardation and Birth Defect Research and 2 Department of Molecular Genetics, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan, 3 Mitsubishi Kagaku Institute of Life Sciences, Tokyo, Japan, 4 Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Gunma, Japan and 5 Stress Disorders Research Team, Tokyo Institute of Psychiatry, Tokyo, Japan
* To whom correspondence should be addressed at: Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan. Tel: +81 423461713; Fax: +81 423461743; Email: kitamura{at}ncnp.gp.jp or kuniokitamura{at}gmail.com
Received March 29, 2009; Revised June 8, 2009; Accepted July 9, 2009
ARX (the aristaless-related homeobox gene) is a transcription factor that participates in the development of GABAergic and cholinergic neurons in the forebrain. Many ARX mutations have been identified in X-linked lissencephaly and mental retardation with epilepsy, and thus ARX is considered to be a causal gene for the two syndromes although the neurobiological functions of each mutation remain unclear. We attempted to elucidate the causal relationships between individual ARX mutations and disease phenotypes by generating a series of mutant mice. We generated three types of mice with knocked-in ARX mutations associated with X-linked lissencephaly (P353R) and mental retardation [P353L and 333ins(GCG)7]. Mice with the P355R mutation (equivalent to the human 353 position) that died after birth were significantly different in Arx transcript/protein amounts, GABAergic and cholinergic neuronal development, brain morphology and lifespan from mice with P355L and 330ins(GCG)7 but considerably similar to Arx-deficient mice with truncated ARX mutation in lissencephaly. Mice with the 330ins(GCG)7 mutation showed severe seizures and impaired learning performance, whereas mice with the P355L mutation exhibited mild seizures and only slightly impaired learning performance. Both types of mutant mice exhibited the mutation-specific lesser presence of GABAergic and cholinergic neurons in the striatum, medial septum and ventral forebrain nuclei when compared with wild-type mice. Present findings that reveal a causal relationship between ARX mutations and the pleiotropic phenotype in mice, suggest that the ARX-related syndrome, including lissencephaly or mental retardation, is caused by only the concerned ARX mutations without the involvement of other genetic factors.
The authors wish to be known that, in their opinion, they should be regarded to contribute equally to this work.
Present address: Department of Pediatrics, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.