A gene for nonsyndromic X-linked mental retardation (MRX77) maps to Xq12-Xq21.33.
Nonsyndromic X-linked mental retardation (MRX) is a highly heterogeneous condition in which mental retardation appears to be the only consistent manifestation. According to the most recent data, 77 MRX families with a lod score of >2 have been mapped and eight genes have been cloned. We hereby report on a linkage analysis performed on a Greek family with apparently nonsyndromic MRX. The affected males have moderate to severe mental retardation, severe speech problems, and aggressive behavior. Two-point linkage analysis with 26 polymorphic markers spanning the entire X chromosome was carried out. We could assign the causative gene to a 27 Mb interval in Xq12-Xq21.33. The maximum LOD score was found for markers DXS1225, DXS8114, and DXS990 at 2.36, 2.06, 2.06, respectively at theta = 0.00. Recombination was observed for DXS983 at the proximal side and DXS6799 at the distal side. Nineteen other MRX families have been described with a partial overlapping disease gene interval in proximal Xq. No mutations were found in the MRX77 family for three known or candidate MRX genes, from this region OPHN1, RSK4, and ATR-X. These data indicate that the Xq12-Xq21.33 interval contains at least one additional MRX gene.
Sismani
Carolina
C
The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
Syrrou
Maria
M
Christodoulou
Kyproula
K
Hamel
Ben
B
Chelly
Jamel
J
Yntema
Helger G
HG
van Bokhoven
Hans
H
Tzoufi
Meropi
M
Georgiou
Ioannis
I
Patsalis
Philippos C
PC
D002874:Chromosome Mapping; D041321:Chromosomes, Human, X; D020732:Cytogenetic Analysis; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D008297:Male; D038901:X-Linked Intellectual Disability / Q000235:genetics* / Q000503:physiopathology; D010375:Pedigree