Linkage analysis in Spanish families with nonspecific X-linked mental retardation: Significant linkage at Xq13-q21.
Mental retardation (MR) is a genetically heterogeneous, clinically variable condition. Many cases of MR are linked to the X chromosome. The aim of this study was to identify candidate loci for nonspecific MR in Spanish samples. We selected seven families with nonspecific MR and a pattern of inheritance compatible with an X-linked disorder and a group of 26 sib pairs of mentally retarded individuals. We performed linkage analysis with a panel of 15 markers evenly distributed along the X chromosome. The study showed linkage to marker DXS8076, located in Xq21.1, by the lod score method (z = 2.11 at straight theta = 0.155) and the nonparametric extended relative pair analysis method (chi(2) = 5.32; P < 0.03). Genetic heterogeneity was found, with an estimated 75% of the families linked at recombination fraction straight theta = 0.10 to the DXS8076 locus (chi(2) = 9.51; P < 0.009). Xq13-q21 is one of the critical regions for X-linked MR previously reported, and our study supports the idea that this region may contain a locus for MR in Spanish patients.
Badenas
C
C
Genetics Service, Hospital Clínic, Villaroel 170, 08036 Barcelona, Spain.
Castellví-Bel
S
S
Volpini
V
V
Jiménez
D
D
Sánchez
A
A
Estivill
X
X
Milà
M
M
D004247:DNA / Q000235:genetics; D005192:Family Health; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D018895:Microsatellite Repeats; D010375:Pedigree; D012984:Software; D013030:Spain; D014960:X Chromosome / Q000235:genetics*
D004247:DNA