Localization of Charcot-Marie-Tooth disease type 1a (CMT1A) to chromosome 17p11.2.

Charcot-Marie-Tooth (CMT) disease type 1a has been previously localized to chromosome 17 using the markers D17S58 and D17S71. In that report we were unable to provide unequivocal localization of the CMT1A gene on either the proximal p or the q arm. Therefore, data from one additional CMT1A family and typing of other probes spanning the pericentromeric region of chromosome 17 (D17S73, D17S58, D17S122, D17S125, D17S124) were analyzed. Multipoint analysis demonstrates convincing evidence (log likelihood difference greater than 5) that the CMT1A gene lies within 17p11.2 and most likely between the flanking markers D17S122 and D17S124.     

Localization of a locus for Charcot-Marie-Tooth neuropathy type Ia (CMT1A) to chromosome 17

Phenotypic data for 71 genetic markers for members of five Caucasian kindreds were tested for linkage with the autosomal dominant mutations causing Charcot-Marie-Tooth (hereditary motor sensory) neuropathy type I, characterized by markedly reduced nerve conduction velocities. Lod score analysis gave no evidence of linkage to the closely linked chromosome 1 loci SPTA1-FY-F5-AT3 and APOA2. In contrast, these mutations were found to map closely (zeta = 10.828, theta = 0.0) to D17S58, an anonymous segment of DNA from 17p11.2-p11.1, and thus define the CMT1A locus. Segregation information data for an inferred recombinant offspring indicated that the CMT1A locus is probably proximal to MYH2, the locus encoding adult skeletal muscle myosin heavy polypeptide 2, which maps to 17p13. Analysis of the lod scores on a per kindred basis gave no evidence of genetic heterogeneity.     

Exclusion analysis of Charcot-Marie-Tooth neuropathy (CMT1) with chromosome 1p markers

We previously described a large five-generation family with autosomal dominant inheritance of hereditary motor and sensory neuropathy type I, or Charcot-Marie-Tooth disease (CMT1). The genetic defect in this family was not linked to the Duffy blood group. We investigated the possibility of a disease locus on the short arm of chromosome 1 using 12 anonymous DNA markers. Two markers, D1S2 and D1S22, showed positive linkage, suggesting the existence of a CMT1 locus on 1p. D1S2 and D1S22 are clustered in the 1p31----p22 region. However, multipoint linkage analysis, including additional DNA markers from this chromosome region, excluded a possible CMT1 locus in this part of chromosome 1.     

Dominant intermediate Charcot-Marie-Tooth neuropathy maps to chromosome 19p12-p13.2

The hereditary disorders of peripheral nerve form one of the most common groups of human genetic diseases, collectively called Charcot-Marie-Tooth (CMT) neuropathy. Using linkage analysis we have identified a new locus for a form of CMT that we have called "dominant intermediate CMT" (DI-CMT). A genomewide screen using 383 microsatellite markers showed strong linkage to the short arm of chromosome 19 (maximum LOD score 4.3, with a recombination fraction (straight theta) of 0, at D19S221 and maximum LOD score 5.28, straight theta=0, at D19S226). Haplotype analysis performed with 14 additional markers placed the DI-CMT locus within a 16.8-cM region flanked by the markers D19S586 and D19S546. Multipoint linkage analysis suggested the most likely location at D19S226 (maximum multipoint LOD score 6.77), within a 10-cM confidence interval. This study establishes the presence of a locus for DI-CMT on chromosome 19p12-p13.2.     

Further evidence of a duplication in 17p11.2 in families with recurrence of HMSN Ia (Charcot-Marie-Tooth neuropathy type Ia)

Five Italian families with recurrence of cases of Charcot-Marie-Tooth disease (type Ia) were analysed using three closely linked DNA probes that detect polymorphisms in the region 17p11.2. The probe pVAW409R3 detected the presence of a duplication in all the affected subjects, but not in the subjects with normal electromyographic (EMG) findings. This observation confirms previous data indicating the association of the duplication with the disease, suggesting that, at least in populations of European origin, the duplication might be the molecular feature diagnostic of the pathological trait.     

Dominant intermediate Charcot-Marie-Tooth type C maps to chromosome 1p34-p35

Dominant intermediate Charcot-Marie-Tooth (DI-CMT) neuropathy is a genetic and phenotypic variant of classical CMT, characterized by intermediate nerve conduction velocities and histological evidence of both axonal and demyelinating features. We report two unrelated families with intermediate CMT linked to a novel locus on chromosome 1p34-p35 (DI-CMTC). The combined haplotype analysis in both families localized the DI-CMTC gene within a 6.3-cM linkage interval flanked by markers D1S2787 and D1S2830. The functional and positional candidate genes, Syndecan 3 (SDC3), and lysosomal-associated multispanning membrane protein 5 (LAPTM5) were excluded for pathogenic mutations.     

The duplication in Charcot-Marie-Tooth disease type 1a spans at least 1100 kb on chromosome 17p11.2

Summary Recently, it has been shown that Charcot-Marie-Tooth disease type 1a (CMT1a) is linked with a duplication of a DNA segment that is detected by probe VAW409R3, and that is located on chromosome 17p11.2. Here, we show that this duplication also contains VAW412R3a, but not A10-41 and EW503. Accounting for the duplication in recombination analysis, we found recombinants between CMT1a and EW301 and EW502, but not with A10-41, VAW409R3, and VAW412R3. Using pulsed-field gel electrophoresis analysis, we estimated the minimal size of the duplicated region in CMT1a patients to be 1100 kb.     

A 1.5-Mb deletion in 17p11.2-p12 is frequently observed in Italian families with hereditary neuropathy with liability to pressure palsies.

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder characterized by recurrent mononeuropathies. A 1.5-Mb deletion in chromosome 17p11.2-p12 has been associated with HNPP. Duplication of the same 1.5-Mb region is known to be associated with Charcot-Marie-Tooth disease type 1 (CMT1A), a more severe peripheral neuropathy characterized by symmetrically slowed nerve conduction velocity (NCV). The CMT1A duplication and HNPP deletion appear to be the reciprocal products of a recombination event involving a repeat element (CMT1A-REP) that flanks the 1.5-Mb region involved in the duplication/deletion. Patients from nine unrelated Italian families who were diagnosed with HNPP on the basis of clinical, electrophysiological, and histological evaluations were analyzed by molecular methods for DNA deletion on chromosome 17p. In all nine families, Southern analysis using a CMT1A-REP probe detected a reduced hybridization signal of a 6.0-kb EcoRI fragment mapping within the distal CMT1A-REP, indicating deletion of one copy of CMT1A-REP in these HNPP patients. Families were also typed with a polymorphic (CA)n repeat and with RFLPs corresponding to loci D17S122, D17S125, and D17S61, which all map within the deleted region. Lack of allelic transmission from affected parent to affected offspring was observed in four informative families, providing an independent indication for deletion. Furthermore, pulsed-field gel electrophoresis analysis of SacII-digested genomic DNA detected junction fragments specific to the 1.5-Mb HNPP deletion in seven of nine Italian families included in this study. These findings suggest that a 1.5-Mb deletion on 17p11.2-p12 is the most common mutation associated with HNPP.     

Evidence for linkage of Charcot-Marie-Tooth neuropathy (CMT1) to apolipoprotein A2 (Apo-A2).

We studied 169 members of 15 families with Charcot-Marie-Tooth neuropathy (CMT1) showing male-to-male transmission and slow motor-nerve conduction velocities. Four of these families were informative for linkage to apolipoprotein A2 on chromosome 1 (1q21-23) with an overall lod score of 2.45 at theta = .001. There was no statistical evidence of genetic heterogeneity.     

Modeling del(17)(p11.2p11.2) and dup(17)(p11.2p11.2) contiguous gene syndromes by chromosome engineering in mice: phenotypic consequences of gene dosage imbalance

Contiguous gene syndromes (CGS) are a group of disorders associated with chromosomal rearrangements of which the phenotype is thought to result from altered copy numbers of physically linked dosage-sensitive genes. Smith-Magenis syndrome (SMS) is a CGS associated with a deletion within band p11.2 of chromosome 17. Recently, patients harboring the predicted reciprocal duplication product [dup(17)(p11.2p11.2)] have been described as having a relatively mild phenotype. By chromosomal engineering, we created rearranged chromosomes carrying the deletion [Df(11)17] or duplication [Dp(11)17] of the syntenic region on mouse chromosome 11 that spans the genomic interval commonly deleted in SMS patients. Df(11)17/+ mice exhibit craniofacial abnormalities, seizures, marked obesity, and male-specific reduced fertility. Dp(11)17/+ animals are underweight and do not have seizures, craniofacial abnormalities, or reduced fertility. Examination of Df(11)17/Dp(11)17 animals suggests that most of the observed phenotypes result from gene dosage effects. Our murine models represent a powerful tool to analyze the consequences of gene dosage imbalance in this genomic interval and to investigate the molecular genetic bases of both SMS and dup(17)(p11.2p11.2).     

Analysis of 17p11.2 chromosome region rearrangements in CMT1 patients from Ukraine

Two intercomplementary methods of 17p11.2 duplication/deletion identification have been elaborated: STR allelic variants analysis and direct PMP22 gene dosage measuring by means of quantitative Real-Time PCR. It has been carried out detection and analysis of 17p11.2 chromosome region rearrangements in CMT1 patients from Ukraine. It has been registered the high level of de novo cases with 17p11.2-duplication. It has been shown the 17p11.2 chromosome region duplication/deletion association with CMT1A and HNPP clinical phenotypes which may be used in differential diagnosis of this type of CMT polyneuropathy. The article is published in the original.     

Identification of novel candidate oncogenes in chromosome region 17p11.2-p12 in human osteosarcoma

Osteosarcoma is the most common primary malignancy of bone. The tumours are characterized by high genomic instability, including the occurrence of multiple regions of amplifications and deletions. Chromosome region 17p11.2-p12 is amplified in about 25% of cases. In previous studies, COPS3 and PMP22 have been identified as candidate oncogenes in this region. Considering the complexity and variation of the amplification profiles for this segment, the involvement of additional causative oncogenes is to be expected. The aim of the present investigation is to identify novel candidate oncogenes in 17p11.2-p12. We selected 26 of in total 85 osteosarcoma samples (31%) with amplification events in 17p11.2-p12, using quantitative PCR for 8 marker genes. These were subjected to high-resolution SNP array analysis and subsequent GISTIC analysis to identify the most significantly amplified regions. Two major amplification peaks were found in the 17p11.2-p12 region. Overexpression as a consequence of gene amplification is a major mechanism for oncogene activation in tumours. Therefore, to identify the causative oncogenes, we next determined expression levels of all genes within the two segments using expression array data that could be generated for 20 of the selected samples. We identified 11 genes that were overexpressed through amplification in at least 50% of cases. Nine of these, c17orf39, RICH2, c17orf45, TOP3A, COPS3, SHMT1, PRPSAP2, PMP22, and RASD1, demonstrated a significant association between copy number and expression level. We conclude that these genes, including COPS3 and PMP22, are candidate oncogenes in 17p11.2-p12 of importance in osteosarcoma tumourigenesis.     

Duplication of the PMP22 gene in 17p partial trisomy patients with Charcot-Marie-Tooth type-1A neuropathy

Autosomal dominant Charcot-Marie-Tooth type-1A neuropathy (CMT1A) is a demyelinating peripheral nerve disorder that is commonly associated with a submicroscopic tandem DNA duplication of a 1.5-Mb region of 17p11.2p12 that contains the peripheral myelin gene PMP22. Clinical features of CMT1A include progressive distal muscle atrophy and weakness, foot and hand deformities, gait abnormalities, absent reflexes, and the completely penetrant electrophysiologic phenotype of symmetric reductions in motor nerve conduction velocities (NCVs). Molecular and fluorescence in situ hybridization (FISH) analyses were performed to determine the duplication status of the PMP22 gene in four patients with rare cytogenetic duplications of 17p. Neuropathologic features of CMT1A were seen in two of these four patients, in addition to the complex phenotype associated with 17p partial trisomy. Our findings show that the CMT1A phenotype of reduced NCV is specifically associated with PMP22 gene duplication, thus providing further support for the PMP22 gene dosage mechanism for CMT1A. Received: 3 May 1995 / Revised: 1 August 1995     

Study of the duplication of 17p11.2-12 chromosome region in the patients with hereditary motor and sensory neuropathy type 1A

Charcot-Marie-Tooth neuropathy (CMT) is one of the most common hereditary disorders, affecting 1:2500 individuals. CMT is a heterogeneous group of disorders characterized by chronic peripheral motor and sensory neuropathy. We have performed the detection of 1.5 Mb CMT1A tandem duplication in 17p11.2-12 chromosome region for autosome-dominant CMT1 patients and their relatives using the analysis of two (CA)n polymorphic microsatellite loci: 17S921 and 17S1358 localised in the duplication region. CMT1A duplication was found in three of five autosome-dominant CMT1 families. It has been shown that CMT1A duplication analysis is important for early differential diagnosis of CMT including prenatal diagnosis and genetic consulting in high risk families.     

Assignment of the human granulocyte colony-stimulating factor receptor gene (CSF3R) to chromosome 1 at region p35-p34.3.

The gene for the granulocyte colony-stimulating factor (G-CSF) receptor (CSF3R) was localized on the p35-p34.3 region of human chromosome 1 by in situ hybridization using human G-CSF receptor cDNA as the probe. Polymerase chain reaction using oligonucleotides specific for the human CSF3R produced a specifically amplified DNA fragment with DNA from mouse A9 cells that contained human chromosome 1 but not other human chromosomes. Localization of the CSF3R on chromosome 1 was further confirmed by the spot-blot hybridization of sorted human chromosomes.     

Assignment of the muscle-eye-brain disease gene to 1p32-p34 by linkage analysis and homozygosity mapping.

Muscle-eye-brain disease (MEB) is an autosomal recessive disease of unknown etiology characterized by severe mental retardation, ocular abnormalities, congenital muscular dystrophy, and a polymicrogyria-pachygyria-type neuronal migration disorder of the brain. A similar combination of muscle and brain involvement is also seen in Walker-Warburg syndrome (WWS) and Fukuyama congenital muscular dystrophy (FCMD). Whereas the gene underlying FCMD has been mapped and cloned, the genetic location of the WWS gene is still unknown. Here we report the assignment of the MEB gene to chromosome 1p32-p34 by linkage analysis and homozygosity mapping in eight families with 12 affected individuals. After a genomewide search for linkage in four affected sib pairs had pinpointed the assignment to 1p, the MEB locus was more precisely assigned to a 9-cM interval flanked by markers D1S200 proximally and D1S211 distally. Multipoint linkage analysis gave a maximum LOD score of 6.17 at locus D1S2677. These findings provide a starting point for the positional cloning of the disease gene, which may play an important role in muscle function and brain development. It also provides an opportunity to test other congenital muscular dystrophy phenotypes, in particular WWS, for linkage to the same locus.     

Hereditary motor and sensory neuropathy (HMSN) IA, developmental delay and autism related disorder in a boy with duplication (17)(p11.2p12)

We present a 6-year-old boy with moderate developmental delay, gait disturbance, autism related disorder and mild dysmorphic features. He was seen for evaluation of his retardation since the age of 2.8 years. At first sight, a cytogenetic analysis showed a normal 46,XY karyotype. Neurological examination at the age of 5.5 years revealed a motor and sensory polyneuropathy. A quantitative Southern blot with probes PMP22 and VAW409 specific for Charcot-Marie-Tooth type 1 (CMT1) disclosed a duplication which confirmed the diagnosis HMSN Ia. Subsequently, GTG banded metaphases were re-evaluated and a small duplication 17p was seen on retrospect. Additional FISH with probe LSISMS (Vysis) specific for the Smith-Magenis region at 17p11.2 again showed a duplication. Both parents had a normal karyotype and the duplication test for CMT1 showed normal results for both of them. The boy had a de novo 46,XY,dup(17)(p11.2p12) karyotype. The present observation confirms previous findings of mild psychomotor delay, neurobehavioural features and minor craniofacial anomalies as the major phenotypic features of dup(17)(p11.2) and dup(17)(p11.2p12); in cases of duplications comprising the PMP22 locus HMSN1 is associated. A recognizable facial phenotype emerges characterized by a broad forehead, hypertelorism, downslant of palpebral fissures, smooth philtrum, thin upper lip and ear anomalies.