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EN
To date, 12 cases of heterozygous Ser72Leu mutations in the peripheral myelin protein 22 have been reported in patients suffering from severe demyelinating form of Charcot-Marie-Tooth disease (CMT1) and congenital hypomyelinating neuropathy (CHN) [MIM# 605253]. In the present study we report two cases of de novo S72L mutations in the PMP22 gene detected in patients of Polish origin suffering from CMT1 disease.
EN
Hereditary neuropathy with liability to pressure palsies (HNPP) is manifested by a spectrum of phenotypes, from the classical HNPP course associated with intermittent nerve palsies to a neuropathy resembling Charcot-Marie-Tooth type 1 (CMT1) disease. The majority of HNPP cases are associated with submicroscopical deletions in the 17p11.2-p12 region containing the PMP22 gene, while PMP22 point mutations are rare, representing about 15% of HNPP cases. In this study, we present a patient manifesting with atypical HNPP phenotype associated with a new Thr99fsX110 mutation in the PMP22 gene. We conclude that all patients who fulfill the electrophysiological criteria of HNPP, even if they lack the typical HNPP phenotype, should be tested for point mutations in the PMP22 gene.
EN
In contrast to mutations in the coding sequences of a genes involved in the pathogenesis of Charcot-Marie-Tooth disease (CMT), little is known about CMT phenotypes resulting from a DNA variants located in regulatory sequences of a given " CMT gene". Charcot-Marie-Tooth type X1 disease (CMTX1) is caused by mutations in the GJB1 gene coding for an ion channel known as connexin, with a molecular mass of 32 kDa (Cx32). Only 0.01% of the GJB1 gene mutations have been reported in its 5' regulatory sequence. Pathogenic mutations occured in the internal ribosome entry site (IRES) are extremely rarely reported in human genetic disorders. To the best of our knowledge, in this study we report for the first time in an Eastern European population, two CMTX1 families in which two pathogenic mutations in the 5' regulatory sequence of the GJB1 gene (c.-529T>C and -459C>T) have been found. The two mutations identified in our study disturb the 5' UTR sequence in two different ways, by affecting the transcription factor SOX10 binding site (c.-529T>C) and by the disrupting IRES element of GJB1 gene (c.-459C>T). These regions are responsible for transcription (SOX10) and initiation of translation (IRES), respectively. On the basis of our findings that, in contrast to the most DNA sequence variants reported in untranslated regulatory regions of genes, the c.-459C>T and c.-529T>C mutations remain pathogenic in the context of different ethnic background.
EN
Little is known about the molecular background of clinical variability of Charcot-Marie-Tooth type 1A (CMT1A) disease and hereditary neuropathy with liability to pressure palsies (HNPP). The CMT1A and HNPP disorders result from duplication and deletion of the PMP22 gene respectively. In a series of studies performed on affected animal transgenic models of CMT1A disease, expression of the PMP22 gene (gene dosage) was shown to correlete with severity of CMT course (gene dosage effect). In this study we hypothesized that single nucleotide polymorphisms (SNPs) located within the 5' regulatory sequence of PMP22 gene may be responsible for the CMT1A/HNPP clinical variability. We have sequenced the PMP22 5' upstream regulatory sequence in a group of 45 CMT1A/HNPP patients harboring the PMP22 duplication (37) /deletion (8). We have identified five SNPs in the regulatory sequence of the PMP22 gene. Three of them i.e. -819C>T, -4785G>T, -4800C>T were detected both in the patients and in the control group. Thus, their pathogenic role in the regulation of the expression of the PMP22 gene seems not to be significant. Two SNPs i.e. -4210T>C and -4759T>A were found only in the CMT patients. Their role in the regulation of the PMP22 gene expression can not be excluded. Additionally we have detected the Thr118Met variant in exon 4 of the PMP22 gene, which was previously reported by other authors, in one patient. We conclude that the 5' regulatory sequence of the PMP22 gene is conserved at the nucleotiode level, however rarely occurring SNPs variant in the PMP22 regulatory sequence may be associated with the gene dosage effect.
EN
Hereditary sensory and autonomic neuropathy type 2 is a rare disorder caused by recessive mutations in the WNK1/HSN2 gene located on chromosome 12p13.33. Phenotype of the patients is characterized by severe sensory loss affecting all sensory modalities. We report a novel homozygous Lys179fsX182 (HSN2); Lys965fsX968 (WNK1/HSN2) mutation causing an early childhood onset hereditary sensory and autonomic neuropathy type 2, with acromutilations in upper and lower limbs, and autonomic dysfunction. To the best of our knowledge this is the first genetically proven case of hereditary sensory and autonomic neuropathy type 2 originating from East Europe.
EN
Charcot-Marie-Tooth (CMT) disease caused by mutations in the GDAP1 gene has been shown to be inherited via traits that may be either autosomal recessive (in the majority of cases) [CMT4A] or autosomal dominant [CMT2K]. CMT4A disease is characterized by an early onset, and a severe clinical course often leading to a loss of ambulation, whereas CMT2K is characterized by a mild clinical course of benign axonal neuropathy beginning even in the 6th decade of life. Clinical data from a GDAP1 mutated patient suggests that the presence of a particular mutation is associated with a certain trait of inheritance. The association of a particular GDAP1 gene mutation and a dominant or recessive trait of inheritance is of special importance for genetic counseling and the prenatal diagnostics as regards severe forms of CMT. In the present study we report on two CMT families in which a newly identified Glu222Lys mutation within the GDAP1 gene segregates both in autosomal dominant and recessive traits. Our study shows that at least some GDAP1 gene mutations may segregate with the CMT phenotype as both dominant and recessive traits. Thus, genetic counseling for CMT4A/CMT2K families requires more extensive data on GDAP1 phenotype-genotype correlations.
EN
Polymorphisms in mitochondrial DNA (mtDNA) were analyzed in 152 samples from the Polish population using restriction enzymes AvaI, BamHI, HaeII, HpaI and PstI. Additionally, each sample was classified into the appropriate haplogroup. When required, appropriate fragments were sequenced to establish the exact polymorphic sites. We found one new morph for PstI and six new morphs for AvaII. Some detected morphs have previously been described as population specific morphs in different regions of the world. All polymorphisms were classified into 31 different haplotypes. 21 of them were detected in single individuals. The Polish population was compared with other populations from different regions. Moreover, we have obtained evidence for mutation hot spots in the mtDNA coding region. Our results indicate that AvaII morph and haplogroup composition of the Polish population is similar to other European populations and has a distribution typical for this part of the world. However, statistically significant differences in haplogroup composition were found between the Polish population and Italian and Finnish populations.
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