Genetic heterogeneity of FG syndrome: a fourth locus (FGS4) maps to Xp11.4-p11.3 in an Italian family.
FG syndrome (FGS, MIM 305450) is a rare X-linked recessive disorder comprising mental retardation and multiple malformations. Various families have been described to date, increasing our knowledge of the phenotype variability and making the clinical diagnosis complex, especially in sporadic patients. The first locus for FG syndrome (FGS1) was linked to chromosome region Xq12-q21.31, but other families have been excluded from this locus. The genetic heterogeneity of FG syndrome has been confirmed by analysis of an X chromosome inversion [inv(X)(q11q28)] in an affected boy and in his mentally retarded maternal uncle, suggesting that an additional locus for FG syndrome (FGS2, MIM 300321) is located at either Xq11 or Xq28. Recently, a third locus (FGS3) has been mapped to Xp22.3. We have identified and clinically characterized an Italian FG family, including 31 members with three affected males in two generations and two obligate carriers. We have excluded linkage to known FGS loci, whereas an extensive study of the whole X chromosome has yielded a maximum LOD score (Z(max)) of 2.66 (recombination fraction=0) for markers between DXS8113 and sWXD805. This new locus for FG syndrome corresponds to a region of approximately 4.6 Mb on the X chromosome.
Piluso
Giulio
G
Dipartimento di Patologia Generale, Facoltà di Medicina e Chirurgia, Seconda Università degli Studi di Napoli, Via Luigi De Crecchio 7, 80138 Naples, Italy.
Carella
Massimo
M
D'Avanzo
Michele
M
Santinelli
Raffaele
R
Carrano
Elena Maria
EM
D'Avanzo
Angelo
A
D'Adamo
Adamo Pio
AP
Gasparini
Paolo
P
Nigro
Vincenzo
V
D000015:Abnormalities, Multiple / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D001526:Behavioral Symptoms / Q000235:genetics; D002675:Child, Preschool; D002874:Chromosome Mapping; D041321:Chromosomes, Human, X; D005145:Face / Q000002:abnormalities*; D005260:Female; D018740:Genetic Heterogeneity; D008040:Genetic Linkage; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D007558:Italy; D008126:Lod Score; D008297:Male; D018895:Microsatellite Repeats; D009123:Muscle Hypotonia / Q000235:genetics; D010375:Pedigree; D013577:Syndrome