Neuroanatomical distribution of ARX in brain and its localisation in GABAergic neurons.
Recent human genetics approaches identified the Aristaless-related homeobox (ARX) gene as the causative gene in X-linked infantile spasms, Partington syndrome, and non-syndromic mental retardation as well as in forms of lissencephaly with abnormal genitalia. The ARX predicted protein belongs to a large family of homeoproteins and is characterised by a C-terminal Aristaless domain and an octapeptide domain near the N-terminus. In order to learn more about ARX function, we have studied in detail Arx expression in the central nervous system during mouse embryonic development as well as in the adult. During early stages of development, Arx is expressed in a significant proportion of neurons in the cortex, the striatum, the ganglionic eminences and also in the spinal cord. In the adult, expression of Arx is still present and restricted to regions that are known to be rich in GABAergic neurons such as the amygdala and the olfactory bulb. A possible role for Arx in this type of neurons is further reinforced by the expression of Arx in a subset of GABAergic interneurons in young and mature primary cultures of cortical neuronal cells as well as in vivo. Moreover, these data could explain the occurrence of seizures in the great majority of patients with an ARX mutation, due to mislocalisation or dysfunction of GABAergic neurons. We also performed ARX wild-type and mutant over-expression experiments and found that the different ARX mutations tested did not modify the morphology of the cells. Moreover, no abnormal cell death or protein aggregation was observed, hence suggesting that more subtle pathogenic mechanisms are involved.
Laboratoire de Génétique et de Physiopathologie des Retards Mentaux, Institut Cochin. Inserm U567, Université Paris V. 24, rue du Faubourg Saint Jacques, 75014 Paris, France.
Karine
K
Poirier
Hilde
H
Van Esch
Gaëlle
G
Friocourt
Yoann
Y
Saillour
Nadia
N
Bahi
Stéphanie
S
Backer
Evelyne
E
Souil
Laetitia
L
Castelnau-Ptakhine
Cherif
C
Beldjord
Fiona
F
Francis
Thierry
T
Bienvenu
Jamel
J
Chelly
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000166:cytology* / Q000196:embryology / Q000254:growth & development; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D000089662:Doublecortin Protein; D004622:Embryo, Mammalian; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D049452:Green Fluorescent Proteins; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D007211:Indoles / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D009419:Nerve Tissue Proteins; D009474:Neurons / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D000091042:Reelin Protein; D012697:Serine Endopeptidases; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection / Q000379:methods; D014404:Tubulin / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
C469264:ARX protein, human; D015816:Cell Adhesion Molecules, Neuronal; C000714847:Dcx protein, mouse; D000089662:Doublecortin Protein; D016326:Extracellular Matrix Proteins; D018398:Homeodomain Proteins; D007211:Indoles; D008164:Luminescent Proteins; D009419:Nerve Tissue Proteins; D000091042:Reelin Protein; D014157:Transcription Factors; D014404:Tubulin; D049452:Green Fluorescent Proteins; C007293:DAPI; D005680:gamma-Aminobutyric Acid; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D012697:Serine Endopeptidases