Segregation of the fragile X mutation from an affected male to his normal daughter.
We report here a family in which the fragile X mutation segregates from an affected grandfather through his normal daughter to an affected grandson. The grandson shows clinical and cytogenetic expression of fragile X syndrome due to a full mutation (large methylated insertion) in the fragile X gene (FMR-1). The mother shows a premutation (small unmethylated insertion) in her FMR-1 gene as the sole manifestation of the fragile X syndrome. The grandfather expresses the fragile X syndrome at the clinical and cytogenetic level, whereas he is mosaic for a methylated full mutation and an unmethylated premutation. The absence of expression of the fragile X mutation when transmitted through an expressing male might present further evidence for genomic imprinting of the FMR-1 gene. Alternatively, it is possible that the grandfather transmitted his premutation to his daughter due to germline mosaicism with both the premutation and the full mutation present in his sperm.
Willems
P J
PJ
Department of Medical Genetics, University of Antwerp-UIA, Belgium.
Van Roy
B
B
De Boulle
K
K
Vits
L
L
Reyniers
E
E
Beck
O
O
Dumon
J E
JE
Verkerk
A
A
Oostra
B
B
D000328:Adult; D001192:Arylsulfatases / Q000097:blood; D002675:Child, Preschool; D005260:Female; D005600:Fragile X Syndrome / Q000235:genetics*; D006801:Humans; D016114:Ichthyosis, X-Linked / Q000235:genetics; D007962:Leukocytes / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D043266:Steryl-Sulfatase
D001192:Arylsulfatases; D043266:Steryl-Sulfatase