[Mechanism of translocation between chromosomes 4q and 10q in facioscapulohumeral muscular dystrophy].
OBJECTIVE
To investigate the translocation between chromosomes 4q and 10q and its putative correlation with facioscapulohumeral muscular dystrophy (FSHD).


METHODS
Double digestion of the genomic DNA of 50 controls and 45 FSHD cases, 16 cases of sporadic FSHD and 19 cases of familial FSHD from 7 families, with restriction enzymes BglII and BlnI was followed by separation and Southern blotting with the probe p13E-11. By Scion Image program, the density of hybridized fragments was analyzed and the 4q:10q density ratio was then calculated to infer the types of 4q-10q translocation. The frequencies of translocation among the controls, sporadic FSHD cases, and familial cases were compared.


RESULTS
In the 95 subjects 4 different translocation types were detected with a translocation rate of 17.89%. Both the rate of 4q-->10q translocation and the rate of 10q-->4q translocation were 8.0% among the healthy controls. Only 4q-->10q translocation was found in sporadic FSHD cases with a frequency of 43.75%, while only 10q-->4q translocation was found in familial FSHD patients with a frequency of 6.89%. The frequency of 4q-->10q translocation in the sporadic FSHD cases was significantly higher than that in the control group (chi(2) = 11.154, P < 0.001), while the frequency of 10q-->4q translocation in the familial FSHD cases was not significantly different from that in the controls (chi(2) = 0.012, P > 0.5).


CONCLUSIONS
Frequent translocations between chromosomes 4q and 10q occur in normal population and FSHD cases, while the 4q-->10q translocation is only related to sporadic FSHD. Excessive loss or conversion (to 10q26) of 4q35 D4Z4 repeats, caused by 4q-10q interactions, may be essential for the mechanism of this disorder.
Wang
Ning
N
Department of Neurology, First Affiliated Hospital of Fujian Medical University, Fuzhou 350005, China.
Wu
Zhi-ying
ZY
Wang
Chao-dong
CD
Wang
Zhi-qiang
ZQ
Lin
Min-ting
MT
Fang
Ling
L
Murong
Shen-xing
SX
D000293:Adolescent; D000328:Adult; D000368:Aged; D002879:Chromosomes, Human, Pair 10; D002894:Chromosomes, Human, Pair 4; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020391:Muscular Dystrophy, Facioscapulohumeral / Q000235:genetics*; D014178:Translocation, Genetic