Synthesis,Characterization, and in Vitro Stability of Chitosan-Methotrexate Conjugates

Pharmaceutical Research -     

Exclusion mapping of 12 X-linked disease loci and 10 DNA probes from the long arm of the X-chromosome

Specific chromosome rearrangements associated with disease entities are invaluable resources for physical mapping. A deletion on the X chromosome of a male leads to the nullisomy for X-linked genes, resulting in the onset of genetic diseases and/or the absence of the DNA probe detectable sequences. This permits the localization of these loci within the deleted area. On the other hand, the region for some other X-linked loci can be excluded from the deleted area according to the absence of the characteristic symptoms of the disease and/or the presence of the hybridization signals. An interstitial deletion on the long arm of the X chromosome of a male has been characterized by high resolution banding. The karyotype of the proband is 46,Y,del(X)(pter----q21.1::q21.33----qter). The regions for 12 X-linked disease loci as well as 10 DNA probes are excluded from the deleted area, and localized either proximally or distally to the deletion. The results also reveal a controversy in the present linkage data concerning the assignment of these loci.     

Axonal excitability in X-linked dominant Charcot Marie Tooth disease

ObjectiveWe investigated peripheral nerve function in X-linked Charcot–Marie–Tooth disease type 1 (CMTX1), and considered the functional consequences of mutant connexin-32.MethodsTwelve subjects (9 female, 3 male) were assessed clinically, by nerve conduction and excitability studies. A model of myelinated axon was used to clarify the contributing changes.ResultsAll subjects had abnormal nerve conduction. Excitability studies on median nerve axons showed greater threshold changes to hyperpolarising currents, with “fanning out” in threshold electrotonus, and modest changes in the recovery cycle. Modelling suggested shortening of internodal length, increase in nodal fast potassium currents, shift of the voltage activation hyperpolarisation-activated cyclic-nucleotide-gated channels, and axonal hyperpolarisation. Plotting threshold versus extent of hyperpolarising threshold change in threshold electrotonus distinguished the CMTX1 patients from other chronic demyelinating neuropathies reported in the literature except hereditary neuropathy with pressure palsies (HNPP).ConclusionsSome measures of axonal excitability are similar in CMTX1 and HNPP (though not the recovery cycle), but they differ from those in other chronic demyelinating neuropathies. The findings in CMTX1 are consistent with known pathology, but are not correlated to neuropathy severity.SignificanceThe findings in CMTX1 could be largely the result of morphological alterations, rather than plasticity in channel expression or distribution.     

Gap junction protein beta 1 (GJB1) mutations and central nervous system symptoms in X-linked Charcot-Marie-Tooth disease

OBJECTIVES: To clarify the clinical variability, including central nervous system (CNS) involvement, in X-linked Charcot-Marie-Tooth disease (CMTX) patients. MATERIAL AND METHODS: We clinically, pathologically and genetically studied six CMTX patients with distinct symptoms and four different GJB1 mutations. RESULTS: One patient with Val63Ile had deafness, low intelligence, saccadic eye movement, upper extremity distal dominant muscle weakness and normal sensation. Another patient with Glu186Lys had severe sensorineural deafness at the age of 6 years, but did not develop muscle weakness until the age of 20 years. Two patients with Arg22Gln had typical CMT1A-like clinical features, no CNS symptoms and obvious onion bulb formations. Two siblings with deletion of the entire GJB1 gene had mild to moderate lower extremity muscle weakness and sensory disturbance without CNS involvement. CONCLUSION: These findings suggest that some gain of function mutations of GJB1 may be related to CNS symptoms because the patients with GJB1 deletion only had peripheral neuropathy, although other unknown associated factors may contribute to their clinical phenotypes.     

Cellular mechanisms of connexin32 mutations associated with CNS manifestations

Both oligodendrocytes and myelinating Schwann cells express the gap junction protein connexin32 (Cx32). Mutations in the gene encoding Cx32 (GJB1) cause the X-linked form of Charcot-Marie-Tooth disease (CMTX). Although most CMTX patients do not have clinical central nervous system (CNS) manifestations, subclinical evidence of CNS dysfunction is common. We investigated the cellular effects of a subgroup of GJB1/Cx32 mutations that have been reported to cause clinical CNS dysfunction. We hypothesized that these mutants have dominant-negative effects on other connexins expressed by oligodendrocytes, specifically Cx45. We expressed these and other Cx32 mutants in communication-incompetent as well as Cx45-expressing HeLa cells, and analyzed the transfected cells by immunocytochemistry and immunoblotting. In communication-incompetent cells, the mutants associated with CNS phenotypes failed to reach the cell membrane and were instead retained in the endoplasmic reticulum (A39V, T55I) or Golgi apparatus (M93V, R164Q, R183H), although rare gap junction plaques were found in cells expressing M93V or R183H. In HeLa cells stably expressing Cx45, these Cx32 mutants showed a similar expression pattern, and did not alter the pattern of Cx45 expression. These results indicate that Cx32 mutants that are associated with a CNS phenotype do not interact with Cx45, but may instead have other toxic effects in oligodendrocytes.     

腓骨肌萎缩症X1型汉族患者电生理和病理特征分析

目的:探讨因GJB1基因突变导致的腓骨肌萎缩症X1型(CMTX1)中国汉族患者的神经电生理特点和病理特征,并进一步分析病理类型与神经电生理间关系。方法:对12个家系经过测序证实为GJB1点突变的35例CMTX1患者的电生理结果进行回顾性分析,对其中来自4个不同家系4例患者进行腓肠神经活检,行超微电镜观察。结果:GJB1基因突变CMTX1患者35例,存在运动神经传导速度(MNCV)的轻、中度减慢,CMAP波幅的减低较MNCV减慢更明显。4例患者腓肠神经病理改变均存在有髓神经纤维数量减少,丛性结构,轴索外髓鞘内间隙,未见典型洋葱头样结构。即为轴索病变同时伴有脱髓鞘病变,且以轴索病变为主。结论:GJB1基因突变的CMTX1表现为中间型,且以轴索病变为主,神经电生理及病理结果表现具有一致性。     

X‐linked Charcot‐Marie‐Tooth disease type 6 (CMTX6) patients with a p.R158H mutation in the pyruvate dehydrogenase kinase isoenzyme 3 gene

Charcot‐Marie‐Tooth disease (CMT) is the most common inherited peripheral neuropathy. Mutations in the pyruvate dehydrogenase kinase isoenzyme 3 (PDK3) gene have been found to cause X‐linked dominant CMT type 6 (CMTX6). This study identified the p.R158H PDK3 mutation after screening 67 probable X‐linked CMT families. The mutation fully segregated with the phenotype, and genotyping the family indicated the mutation arose on a different haplotype compared with the original Australian CMTX6 family. Results of bisulphite sequencing suggest that methylated deamination of a CpG dinucleotide may cause the recurrent p.R158H mutation. The frequency of the p.R158H PDK3 mutation in Koreans is very rare. Magnetic resonance imaging revealed fatty infiltration involving distal muscles in the lower extremities. In addition, fatty infiltrations were predominantly observed in the soleus muscles, with a lesser extent in tibialis anterior muscles. This differs from demyelinating CMT1A patients and is similar to axonal CMT2A patients. The clinical, neuroimaging, and electrophysiological findings from a second CMTX6 family with the p.R158H PDK3 mutation were similar to the axonal neuropathy reported in the Australian family.     

Unusual features of central nervous system involvement in CMTX associated with a novel mutation of GJB1 gene

In this study, we report a novel connexin 32 (CX32) mutation associated with cognitive impairment and a differential degree of peripheral nerve involvement. We present clinical, electrophysiological, and neuroimaging data on a family with X‐linked Charcot‐Marie‐Tooth disease caused by a 41A>G mutation of the gap junction protein beta 1 (GJB1) gene. The proband and her sister presented with a severe neuropathy with subclinical cognitive impairment; the proband's brother showed severe cognitive impairment and a mild neuropathy. This family report confirms that Charcot‐Marie‐Tooth type X is a clinically heterogeneous group, with great variability of phenotypes, possible severe involvement in females and clinical signs of cognitive impairment. Thus, this novel mutation should be added to the group of CX32 mutations with a central nervous system phenotype.     

A case with CMTX1 disease showing transient ischemic-attack-like episodes

Charcot-Marie-Tooth (CMT) disease is a hereditary neurologic disease which affects the sensorial and motor fibers of the peripheral nerves. CMTX1 is an X-linked dominantly inherited subtype of CMT and is caused by mutations in gap junction beta 1 gene (GJB1). A small proportion of GJB1 mutations are associated with recurrent central nervous system findings. We describe a 15-year-old male patient with CMTX1 who had stroke-like findings along with foot deformities and peripheral neuropathy. Strokes and stroke-like attacks are rarely seen in children and adolescents. Herein, neurological signs, MRI findings and genetic results of a CMTX1 case are presented and discussed.