Elongation of (CTG)n repeats in myotonic dystrophy protein kinase gene in tumors associated with myotonic dystrophy patients.

Length of (CTG)n triplet repeats in myotonic dystrophy protein kinase gene (DMPK) was estimated in tumors, normal tissues of the same organs, muscles, and leukocytes from three myotonic dystrophy (DM) patients and a non-DM patient. Using cDNA 25 as a probe, a Southern blot analysis of EcoRI- and BglI-digested DNA from these tissues demonstrated the longest expansion of the repeats in the tumors of DM patients. In all tissues from a non-DM patient, the repeat length was confirmed to be stable by PCR analysis. Our data suggest that expanded (CTG)n repeat in tumor tissues may have increased the instability. This study emphasizes the importance of a long-term prospective study on the incidence of tumors in DM to clarify the pathological interrelation between the two entities.     

Cognitive impairment and (CTG)n expansion in myotonic dystrophy patients.

BACKGROUND: Myotonic dystrophy (DM) is a genetic multisystemic disease with muscular, endocrine, ocular, cardiac and cognitive impairment. The molecular basis of the disease has been identified in an unstable base triplet (CTG)n repeat located in the 3' untranslated region of the miotonin protein-kinase (MT-PK) gene on the long arm of chromosome 19. Cognitive impairment could be a direct expression of this genetic alteration at the central nervous system (CNS) level rather than a consequence of the neuromuscular impairment. To explore this hypothesis, we tested a group of genetically diagnosed, adult onset DM, of their nonaffected relatives (NAR), of patients with spinal muscle atrophy (SMA), and of normal controls using the Wechsler Adult Intelligence Scale (WAIS). METHODS: Seventeen adult-onset DM patients, 9 NAR, 10 SMA patients and 20 unrelated normal controls (NC) were studied. Clinical, neuromuscular and neuropsychiatric evaluation, which included WAIS and the Schedule for Affective Disorders and Schizophrenia (SADS), were performed on the four groups. DM, NAR and NC were also assessed by a neurophysiological (P300) evaluation. A DNA analysis was performed in DM and in NAR to measure presence and magnitude of CTG expansion. RESULTS: We found a statistically significant difference between verbal (p < .0003), nonverbal (p < .0001) and total (p < .0001) IQ of DM patients compared to IQs of NAR, SMA and NC. Seven out of 11 WAIS subtests were significantly and consistently lower in DM patients compared to SMA and/or NC. In DM patients there was a statistically significant negative correlation between nonverbal (r = -.68; p < .002) and total (r = .59; p < .01) IQ and (CTG)n. Patients with DM had a significantly lower P300 amplitude compared to NAR and NC. CONCLUSIONS: Our study indicates that in DM there is a mild but significant cognitive impairment which correlates with the degree of CTG expansion and it is not dependent on the neuromuscular impairment; however further studies with larger groups of patients and controls are suggested to confirm our results, due to the small sample size and to a possible effect of educational level in our patients.     

The DMWD protein from the myotonic dystrophy (DM1) gene region is developmentally regulated and is present most prominently in synapse-dense brain areas

The DMWD gene is located in the myotonic dystrophy (DM1) gene cluster on 19q, just upstream of the DMPK gene. RNA and protein products of this gene are ubiquitously expressed in all adult tissues, but occur most abundant in testes and brain. Altered expression of DMWD mRNA in DM1 patients has been observed, suggesting a role of the DMWD gene products in disease manifestation. Here we focussed on DMWD expression in mouse brain and followed mRNA and protein levels and (intra)cellular location in developing brain in vivo as well as in differentiating neuronal cell cultures in vitro. In the interval between postnatal days P7 and P21, the steady-state level of DMWD mRNA remained constant, whereas the DMWD protein (doublet of 70 kDa) level gradually increased during the same period. The DMWD protein was expressed throughout the brain, at a low level in glial cells, more prominently in neurons and specifically in the neuropil of brain areas with a high density of synaptic connections. Intracellularly, DMWD was dispersed in a punctuate fashion throughout the neural cell body, the nucleus and the dendrites with their synapses, but was excluded from axons. Based on these findings and on new literature data concerning the role of DMWD homologs in lower eukaryotes, we discuss the possible role of DMWD in the brain-related symptoms seen in DM1 patients.     

Reduction in excess daytime sleepiness by modafinil in patients with myotonic dystrophy

Patients with myotonic dystrophy frequently suffer from excess daytime sleepiness, which can be a significant cause of disability. Previous studies have indicated that this excess daytime sleepiness is only occasionally due to obstructive sleep apnoea and may be principally of central nervous system origin. Modafinil has been successfully used to treat narcolepsy, a central disorder causing excess daytime sleepiness. We have investigated the use of this drug in myotonic dystrophy patients with excess daytime sleepiness. Patients were recruited from a clinic population on the basis of screening with the Epworth Sleepiness Scale. Patients scoring 10 and above were invited to participate in a randomized double-blind crossover trial of modafinil versus placebo, with four weeks in each arm of the study separated by a 2-week washout period. Patients were assessed by polysomnography at baseline. The primary outcome measures were change in both the Epworth Sleepiness Scale and a modified Maintenance of Wakefulness Test, which were measured at the start of each arm of the trial and in week 3 of each intervention period. In agreement with previous smaller studies, sleepiness is not correlated with CTG expansion size. Treatment with modafinil showed a non-significant reduction in median Epworth Sleepiness Scale. However, the median Maintenance of Wakefulness Test score was prolonged by treatment (31.7-40 min, P=0.006). There were no significant adverse cardiac effects of the drug in this group of patients (resting 12 lead and 24 h ECG monitoring). Selected patients with myotonic dystrophy and excess daytime sleepiness may benefit from modafinil. In this patient group the Epworth Sleepiness Scale may not be the most reliable measure of sleepiness. Despite the potential for cardiac disease in these patients, the drug was well tolerated with no adverse effects.     

伴有脑部损害的强直性肌营养不良10例临床分析

目的分析伴有脑部损害的强直性肌营养不良(DM)的临床特点,以提高对DM疾病的认识及诊断水平。方法收集至我院就诊的伴有脑损害的临床诊断为DM的患者,对患者的临床资料进行分析。结果 10例患者均为慢性起病,以双手无力、活动不灵活起病多见,其中6例有家族史,部分病例伴有白天嗜睡,智能下降、肺部感染、呼吸衰竭、心脏、眼部、内分泌等其他多系统损害。10例均行肌电图检查提示肌源性损害,均发现有肌强直电位。10例均行头部磁共振(MRI)检查,8例可见额顶颞叶白质不同程度的脱髓鞘,2例出现脑室扩大、脑积水,1例可见前床突状脑膜瘤、脑部多发软化灶。2例行肌活检,主要表现为部分肌纤维萎缩,变性、坏死肌纤维,核内移及肌浆块形成。3例患者行肌肉MRI,显示肌肉弥漫性异常信号; 1例行肺部CT示肺部感染,2例行强直性肌营养不良蛋白激酶(DMPK)基因CTG重复序列分析示拷贝数超过正常范围。结论 DM是一种累及多系统的遗传性疾病,除常见累及肌肉、心脏、内分泌、眼部系统外,还常累及脑部白质、脑室脑膜、呼吸系统,对诊断DM的患者应进行头部和呼吸系统方面的检查;此外,肌肉MRI对DM的诊断有一定帮助。     

强直性肌营养不良患者肌肉组织中myostatin基因mRNA表达增加

目的 研究肌肉生长抑制素myostatin基因的mRNA在强直性肌营养不良患者肌肉组织中的表达情况.方法 采用半定量RT-PCR检测4例强直性肌营养不良患者和4名非肌肉病对照者肌肉组织中myostatin mRNA的表达.结果 2组肌肉组织中均有myostatin基因的mRNA表达.强直性肌营养不良患者肌肉组织中myostatin基因的mRNA的表达指数为2.25±1.04,明显高于对照组肌肉组织的0.34±0.15,差异有统计学意义(t=3.707,P=0.01).表达指数与肌肉萎缩之间无明显相关(r=-0.719,t=2.95,P＞0.05).结论 强直性肌营养不良患者肌肉组织中myostatin基因mRNA表达显著上调,可能是强直性肌营养不良患者肌肉萎缩的原因之一.     

42例强直性肌营养不良症(MYD)电生理表现

为了研究探讨MYD患者的电生理特点,本文对42例MYD病人进行了肌电图(EMG)、神经传导速度(NCV)和体感诱发电位(SEPs)检查。结果发现,全部患者均有电肌强直表现,其放电频率以拇短展肌最高。28%的病人发现NCV减慢,以运动神经为主,且早年症状组NCV异常率明显高于成年症状组病人。SEPs异常检出率为24%,且多数合并周围神经损害。结论:42例MYD患者存在着广泛的电生理异常,且早年症状组较成年症状组病人更为常见。     

Computed tomographic findings of brain and skull in myotonic dystrophy.

Twenty-four patients with myotonic dystrophy underwent computed tomographic examination of the skull and brain. The results were compared with those of 20 normal subjects of similar age and sex distribution. Microcephaly and thickening of the calvarium were frequently observed. Some cases showed basal ganglia calcification. Our findings confirm that cranial hyperostosis and brain pathology is a common manifestation of this systemic disease.     

Event-related potentials (P300) in myotonic dystrophy

The P300 component of the auditory event-related potential in 8 patients with myotonic dystrophy was studied and compared with that of 13 healthy controls. Abnormalities of P300 (prolongation of the latency and/or decrease of the amplitude) were observed in 6. These observations imply that the function of cognitive and information processing are impaired in myotonic dystrophy.     

Decreased expression of myotonic dystrophy protein kinase and disorganization of sarcoplasmic reticulum in skeletal muscle of myotonic dystrophy

Pathological expression of myotonic'dystrophy protein kinase (DMPK) in skeletal muscle of myotonic dystrophy (DM) was studied by Western blot analysis, immunohistochemistry, and immunoelectron microscopy of DMPK. Western blot analysis showed that DMPK protein in DM skeletal muscles dramatically decreased. DMPK-positive muscle fibers showed typical DM pathological changes such as type I atrophy, central nuclei, nuclear chains, and sarcoplasmic masses. In degenerated DMPK-positive muscle fibers, cross-striated bands disappeared, and irregular granular DMPK-positive materials appeared in sarcoplasm. By immunoelectron microscopy, DMPK was localized in the terminal cisternae of the sarcoplasmic reticulum (SR) in DM muscle. Swollen DMPK-positive SRs were detected between well preserved myofibrils in the early stage of DM muscle degeneration, and degenerated intramembranous structures with DMPK and an accumulation of mitochondria were observed between disorganized myofibrils in degenerated DM muscle. We concluded that SR is the primary site of the degeneration of DM skeletal muscle and that the decreased DMPK might cause dysregulation of intracellular calcium metabolism, which is followed by DM muscle degeneration.     

Developmental expression of myotonic dystrophy protein kinase in brain and its relevance to clinical phenotype

To investigate the pathophysiologic role of myotonic dystrophy protein kinase (DMPK) in the brain in myotonic dystrophy (MD), the developmental characteristics of DMPK immunoreactivity in the central nervous system and its alteration with disease were studied. Eleven patients’ brain with MD (5 congenital form, 6 adult form) were examined by immunohistochemistry using a specific antibody against synthetic DMPK peptides, anti-peptide DM1, and compared with 30 control brains, including 16 age-matched controls. In controls, DM1-immunoreactive neurons appeared in the early fetal frontal cortex and cerebellar granule cell layer, persisting through 29 weeks of gestation and then disappearing. In contrast, immunoreactive neurons continued to persist in the cerebral cortex and cerebellar granule cell layer of MD patients. When we counted DM1-immunoreactive neurons, the increase over controls was greater in the congenital form of MD than in the adult form, and was greater in the cerebrum than in the cerebellum in both forms of MD. DM1 immunostaining was predominantly nuclear, mirroring Western blotting of subcellular fractions. Differences in DM1 expression related to development and to the two forms of MD may be closely related to the pathogenesis of mental retardation in this disease. Received: 30 July 1999 / Revised: 21 January 2000 / Accepted: 1 February 2000     

Proton magnetic resonance spectroscopy of brain in congenital myotonic dystrophy

Volume selective proton magnetic resonance spectroscopy of brain was performed on a 1.5 T magnet in 5 patients with congenital muscular dystrophy and compared to the results in 46 healthy children and 1 healthy adult. Peaks of N-acetyl aspartate, choline, and creatine but not lactate, were observed in both groups on proton magnetic resonance spectroscopy. Spectroscopy of controls revealed an increase with advancing age in the ratio of N-acetyl aspartate/choline and N-acetyl aspartate/creatine and a decrease in the choline/creatine ratio. In patients with congenital myotonic dystrophy, the N-acetyl aspartate/choline ratio did not increase with advancing age, but the N-acetyl aspartate/creatine ratio did. The choline/creatine ratio decreased with advancing age, which matched the results of controls. At any age older than 4 years, the N-acetyl aspartate/choline and N-acetyl aspartate/creatine ratios were lower in patients with congenital myotonic dystrophy than in controls. The choline/creatine ratio did not differ between congenital myotonic dystrophy and controls. These results suggest that in patients with congenital myotonic dystrophy N-acetyl aspartate decreases and there exists a developmental disorder of neurons in brain.