Male embryonic mice with mutations in the X-linked aristaless-related homeobox gene (Arx) developed with small brains due to suppressed proliferation and regional deficiencies in the forebrain. These mice also showed aberrant migration and differentiation of interneurons containing γ-aminobutyric acid (GABAergic interneurons) in the ganglionic eminence and neocortex as well as abnormal testicular differentiation. These characteristics recapitulate some of the clinical features of X-linked lissencephaly with abnormal genitalia (XLAG) in humans. We found multiple loss-of-function mutations in ARX in individuals affected with XLAG and in some female relatives, and conclude that mutation of ARX causes XLAG. The present report is, to our knowledge, the first to use phenotypic analysis of a knockout mouse to identify a gene associated with an X-linked human brain malformation.
Bibliographical noteFunding Information:
The authors thank L.R. Rubenstein for providing Titf1; M. Price for Dlx1; V. Pachnis for Lhx6; J. Mason for Wntb8; S. Retaux for Lhx9; B. Condie, C. Gerfen and Y. Yanagawa for Gad1; I. Mason for antibody against Hsd3b1; Y. Motegi, Y. Nakahara, A. Suehiro, T. Akiyama, A. Miyake, A. Oshida and A. Ohwaki for technical support; Y. Arimatsu, H. Takahashi, S. Tanaka and B. Capel for helpful discussion; H. Nakamura and H. Okamoto for their encouragement; and the parents of children with XLAG who were studied. This work was supported in part by grants-in-aid for scientific research to K.M. from the Ministry of Education, Science, Sports, and Culture of Japan and by a grant from the US National Institutes of Health to W.B.D.
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