面肩肱型肌营养不良症患者染色体4q-10q相互易位机制的初步研究

目的　探讨染色体 4q与 10q间相互易位现象及其与面肩肱型肌营养不良症 (FSHD)的关系。方法　BglII/BlnI双酶切、凝胶电泳分离 5 0名正常对照及 45例FSHD患者的基因组DNA ,采用p13E 11探针Southern杂交 ,应用ScionImage软件检测并校正 4q 及 10q 型杂交片段的信号强度值 ,计算 4q :10q剂量比来判断易位情况 ,比较对照组与FSHD患者发生易位频率的差异。结果　 95名检测对象中共检测到 4种易位情况 ,总易位频率为 17 89%。对照组中 4q→ 10q型易位和 10q→ 4q型易位均占 8 0 %;而散发性患者只检测到 4q→ 10q易位 ,发生频率为 43 75 %;家族性患者只检测到 10q→4q易位 ,频率为 6 89%。散发性患者 4q→ 10q易位发生频率明显高于对照组 ( χ2 =11 15 4,P <0 0 0 1) ,而家族性患者 10q→ 4q易位频率与对照组间无差异 ( χ2 =0 0 12 ,P >0 5 )。结论　正常人群及FSHD患者均存在 4q35区的不稳定性及 4q 10q相互易位现象 ;4q→ 10q易位的发生与散发型FSHD的发病密切相关 ,与家族型FSHD关系较小 ;4q 10q的相互作用引起 4q35区的D4Z4重复单位丢失或转移至10q2 6 ,可能是导致患者发病的重要因素。

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). CONCLUSION: 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.