Cardani R, Mancinelli E, Sansone V, Rotondo G, Meola G
Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italy.
Eur J Histochem. 2004 Oct-Dec;48(4):437-42. doi: 10.4081/918.
Myotonic dystrophy type 2 (DM2) is a dominantly inherited disorder with multisystemic clinical features, caused by a CCTG repeat expansion in intron 1 of the zinc finger protein 9 (ZNF9) gene. The mutant transcripts are retained in the nucleus forming multiple discrete foci also called ribonuclear inclusions. The size and the somatic instability of DM2 expansion complicate the molecular diagnosis of DM2. In our study fluorescence-labeled CAGG-repeat oligonucleotides were hybridized to muscle biopsies to investigate if fluorescence in situ hybridization (FISH), a relatively quick and simple procedure, could be used as a method to diagnose DM2. When FISH was performed with (CAGG)5 probe, nuclear foci of mutant RNA were present in all genetically confirmed DM2 patients (n=17) and absent in all patients with myotonic dystrophy type 1 (DM1; n=5) or with other muscular disease (n=17) used as controls. In contrast, foci were observed both in DM1 and DM2 myonuclei when muscle tissue were hybridized with (CAG)6CA probe indicating that this probe is not specific for DM2 identification. The consistent detection of ribonuclear inclusions in DM2 muscles and their absence in DM1, in agreement with the clinical diagnosis and with leukocyte (CCTG)n expansion, suggests that fluorescence in situ hybridization using (CAGG)5 probes, may be a specific method to distinguish between DM1 and DM2. Moreover, the procedure is simple, and readily applicable in any pathology laboratory.
2型强直性肌营养不良症（DM2）是一种具有多系统临床特征的常染色体显性遗传病，由锌指蛋白9（ZNF9）基因第1内含子中的CCTG重复序列扩增引起。突变转录本保留在细胞核中，形成多个离散的病灶，也称为核糖核蛋白包涵体。DM2扩增的大小和体细胞不稳定性使DM2的分子诊断变得复杂。在我们的研究中，荧光标记的CAGG重复寡核苷酸与肌肉活检组织杂交，以研究相对快速简单的荧光原位杂交（FISH）方法是否可用于诊断DM2。当用（CAGG）5探针进行FISH时，所有基因确诊的DM2患者（n = 17）均出现突变RNA的核病灶，而所有1型强直性肌营养不良症（DM1；n = 5）患者或用作对照的其他肌肉疾病患者（n = 17）均未出现。相反，当肌肉组织与（CAG）6CA探针杂交时，在DM1和DM2肌细胞核中均观察到病灶，这表明该探针并非DM2特异性识别探针。DM2肌肉中核糖核蛋白包涵体的一致检测以及DM1中未检测到，与临床诊断和白细胞（CCTG）n扩增一致，表明使用（CAGG）5探针的荧光原位杂交可能是区分DM1和DM2的特异性方法。此外，该方法简单，可在任何病理实验室轻松应用。
