Severe Charcot-Marie-Tooth neuropathy type 1A with 1-base pair deletion and frameshift mutation in the peripheral myelin protein 22 gene.

A 27-year-old man with negative family history and both parents with normal neurological evaluation and motor nerve conduction velocities (MNCVs) showed onset of severe weakness of feet at 4 years of age. Subsequently he developed left equinovarus deformity, thoracic scoliosis, ulnar nerve enlargement, areflexia, distal hypesthesia and slowing of MNCVs for median and ulnar nerves (15-25 m/sec). Molecular genetic studies showed deletion of one nucleotide (G330) (codon 94) in exon 3 of the PMP22 gene associated with frameshift mutation.

Dejerine-Sottas neuropathy in mother and son with same point mutation of PMP22 gene.

We studied a 25-year-old black woman with healthy parents and her 2-year, 11-month-old son. Her motor development was delayed and she started to walk with support when she was 6 years old. She never walked independently and had always used a wheelchair. Neurological evaluation showed severe weakness and atrophy of her feet, legs, and hands, bilateral pes cavus and hammertoes, corrected scoliosis, hypesthesia for proprioception and vibration sense in both feet and ankles, and areflexia. She had normal intelligence. Her son also had delayed motor milestones and was still unable to stand and walk independently at almost 3 years. Neurological evaluation revealed diffuse muscle hypotonia and weakness with generalized areflexia and normal intelligence. No muscle atrophies or feet deformities were noticed. Nerve conduction velocities showed significant slowing (less than 5 m/s) with prolonged distal latencies (above 30 ms). Compound motor action potential amplitudes were markedly reduced. Electromyography revealed polyphasic motor unit potentials. Molecular genetic studies indicated a Trembler type missense point mutation of exon 4 of the peripheral myelin protein 22 gene that led to the substitution of a spartic acid for glycine in both the mother and her son. Her parents showed normal DNA studies.

Autosomal dominant Charcot-Marie-Tooth axonal neuropathy mapped on chromosome 7p (CMT2D).

Clinical, electrophysiological and genetic linkage studies were performed on a large autosomal dominant family with Charcot-Marie-Tooth axonal neuropathy type 2 (CMT2) with 38 members of which 14 were affected. Onset of the disease was between 16 and 30 years of age with weakness and atrophy of the hands more severe than of the feet with slow progressive course in 12 patients. Deep tendon reflexes were absent in the upper extremities and decreased in the lower extremities. There was distal hypesthesia for touch, proprioception and vibration sense for the hands more than for the feet. Motor nerve conduction velocities showed normal values (48-53 M/s) with normal latencies (2-3 msec) and electromyography revealed signs of denervation. Genetic linkage analysis used 167 short tandem repeat markers (STRPs) spaced throughout the 22 autosomes. Linkage to the short arm of chromosome 7 at 7p14 was found using the marker D7S435 (Z = 4.83 at theta = 0). Flanking markers were D7S1808 and D7S1806 and the genetic distance between them was 6.8 cM. The multipoint linkage analysis gave a peek multipoint lod score of 6.89 between the markers D7S1808 and D7S435. Linkage analysis showed significantly negative lod scores (with values less than -2) with markers of chromosomes 1 and 3 where CMT axonal forms have been previously mapped. PFGE analysis indicated the absence of the CMT1A duplication. Our findings are consistent with a new genetic type of axonal CMT neuropathy designated by us as CMT2D. Potential candidate genes are multiple T-cell gamma receptor genes which map to the same cytogenetic interval as CMT2D neuropathy.

Mutations of the noncoding region of the connexin32 gene in X-linked dominant Charcot-Marie-Tooth neuropathy.

We studied two families with X-linked dominant Charcot-Marie-Tooth neuropathy. The clinical findings included onset around age 14 years, with moderate weakness of feet extensors and palmar and dorsal interossei, areflexia, distal hypesthesia, and slow progressivity. Motor nerve conduction velocities showed slowing (20 to 30 m/sec) and EMGs were normal. Genetic linkage analysis revealed positive lod scores with the markers of the Xq13.1 region in family 2, but was noninformative in family 1. There were no point mutations in the connexin32 gene coding region. Instead, family 1 revealed a T-to-G transversion at position -528 relative to the ATG start codon, whereas family 2 showed a C-to-T transition at position -458. The first mutation is located in the nerve-specific connexin32 promoter just upstream of the transcription start site, the second is located in the 5' untranslated region of the mRNA.

Correlation between connexin 32 gene mutations and clinical phenotype in X-linked dominant Charcot-Marie-Tooth neuropathy.

We studied the relationship between the genotype and clinical phenotype in 27 families with dominant X-linked Charcot-Marie-Tooth (CMTX1) neuropathy. Twenty-two families showed mutations in the coding region of the connexin32 (cx32) gene. The mutations include four nonsense mutations, eight missense mutations, two medium size deletions, and one insertion. Most missense mutations showed a mild clinical phenotype (five out of eight), whereas all nonsense mutations, the larger of the two deletions, and the insertion that produced frameshifts showed severe phenotypes. Five CMTX1 families with mild clinical phenotype showed no point mutations of the cx32 gene coding region. Three of these families showed positive genetic linkage with the markers of the Xq13.1 region. The genetic linkage of the remaining two families could not be evaluated because of their small size.

A Dejerine-Sottas neuropathy family with a gene mapped on chromosome 8.

The Patient is a 55-year-old black male who belongs to a large family with 9 affected relatives with autosomal dominant Dejerine-Sottas neuropathy (DSN). Onset of his condition was at 2 years of age with steppage gait followed by severe progressive weakness, atrophy, and sensory loss of his legs and hands accompanied by areflexia and thoracolumbar kyphoscoliosis. The patient became wheelchair confined at age 38. At around age 42, the left shoulder became dislocated and the humeral head underwent aseptic necrosis (Charcot joint). Nerve conduction studies showed absent motor and sensory responses for all major nerves tested. Genetic linkage suggested mapping of this DSN gene on chromosome 8qter. A younger brother with similar neurological findings also demonstrated Charcot joints with bone destruction of the joints of the fourth and fifth fingers.

Dejerine-Sottas disease with de novo dominant point mutation of the PMP22 gene.

We studied a 33-year-old woman with a negative family history. Both of her parents were examined clinically by nerve conduction velocities (NCVs) and EMG, with normal results. The clinical onset of her condition was at 24 months, with severe weakness and atrophy of her feet and hands, but the proximal muscles were relatively spared. She had bilateral pes cavus, distal weakness and hypesthesia for touch and proprioception, areflexia, claw hands, and severe thoracolumbar kyphoscoliosis. NCVs showed absent motor and sensory responses and EMG revealed diffuse fibrillation potentials. Molecular genetic studies indicated a de novo dominant missense point mutation of exon 3 of the peripheral myelin protein 22 gene at nucleotide 264 that caused the replacement of serine with leucine.

New point mutations and deletions of the connexin 32 gene in X-linked Charcot-Marie-Tooth neuropathy.

The purpose of this study was the identification of new mutations of the connexin 32 (CX32) gene in CMTX families. We report six new mutations of the CX32 gene including two medium sized (29 and 18 bp) deletions. The clinical phenotype is consistent with CMT peripheral neuropathy in all patients. Four families show both male and female patients, with more severe symptoms in males. The disease is asymptomatic in females in two families. The clinical deficit in CMTX families Nos 1, 2 and 4 with missense mutations of the CX32 gene was mild or moderate. Severe weakness of the feet and hands was present in CMTX family No. 5 with a G insertion and family No. 6 with a 29 bp deletion in the carboxyl terminal region of the CX32 gene. Most likely the severe clinical impact in those families was related to frame shift and premature termination of the protein.

Point mutations of the connexin32 (GJB1) gene in X-linked dominant Charcot-Marie-Tooth neuropathy.

Ten families with X-linked dominant CMT neuropathy (CMTX1) were screened for point mutations of the connexin32 (Cx32, GJB1) gene. Two families showed missense mutations, respectively an A-->G transition at amino acid 102 (glutamate to glycine) and a C-->T transition at amino acid 142 (arginine to tryptophan). Three families showed nonsense mutations, respectively a C-->T transition at amino acid 22 (arginine to stop) a G-->T transversion at amino acid 186 (glutamate to stop), and a T-->A transversion at amino acid 217 (cysteine to stop). Five CMTX1 neuropathy families showed no evidence of point mutations of the connexin32 coding sequence. These findings suggest that the CMTX1 neuropathy genotype is heterogeneous or the result of promoter mutations, 3'-untranslated region mutations or exon/intron splice site mutations. Four of the reported mutations created or destroyed restriction enzyme sites: a HaeIII restriction enzyme site was destroyed by the mutation at amino acid position 22, a HpaII site was eliminated at amino acid position 142, a Bfal restriction site was created by the mutation at amino acid 186 and a Ddel restriction site was created by the mutation at amino acid 217. These changes allowed us to test family members for the mutations and observe the segregation of the disease with the mutations.

Screening of dominantly inherited Charcot-Marie-Tooth neuropathies.

Sixty-three families with dominantly inherited Charcot-Marie-Tooth (CMT) neuropathies including 730 subjects (total) from which 356 affected were studied clinically, electrophysiologically (MNCVs and EMGs), by genetic linkage, and screened for DNA duplication. Thirty-eight families (60.3%) were type 1A (demyelinating CMT mapped on chromosome 17). DNA duplication was present in 36 families (94.8% of CMT1A families). One CMT1A family (2.6%) showed no duplication but suggested genetic linkage with markers of chromosome 17. One CMT1A family (2.6%) revealed nonduplication in some affected members and duplication in other affected members. The disease in that family segregated with the same chromosome 17 markers regardless of duplication status. The other CMT families with dominant inheritance but without duplication included one family with CMT1B (demyelinating CMT mapped on chromosome 1) (1.6%), 14 families with CMT2 axonal neuropathy (22.2%), and 10 families with X-linked dominant CMT (15.9%).

Charcot-Marie-Tooth neuropathy type 1A with both duplication and non-duplication.

We studied a family with nine of twenty members affected with Charcot-Marie-Tooth disease type 1A (CMT1A). The proband and her four affected sibs showed no duplication of the 17p11.2-p12 (CMT region). Two of the proband's affected daughters and three affected grandchildren showed duplication of the PMP-22 gene and of the marker VAW409R3 but not of the markers VAW412R3 and EW401. Pulsed field gel electrophoresis (PFGE) revealed a 220 kb SacII fragment in one CMT1A patient with duplication instead of a 500 kb SacII fragment as previously reported (1, 3, 4, 6-9). Our findings suggest a smaller size of the duplication in this CMT1A family. The disease segregates with the same haplotype in both duplicated and nonduplicated CMT1A patients. The clinical phenotype showed more severe weakness with earlier onset and motor nerve conduction velocities were characterized by more significant slowing in the patients with duplication than in the patients who did not show duplication.

Mapping of the gene for X-linked dominant Charcot-Marie-Tooth neuropathy.

We performed a clinical study and linkage analysis on 278 subjects (66 affected) belonging to eight families with X-linked dominant Charcot-Marie-Tooth (CMT) neuropathy. This form affects 11.8% of CMT patients in Iowa. Motor nerve conduction velocities (MNCVs) were significantly slowed consistent with type 1 CMT. Fifty-six obligate carriers manifested mild distal weakness, localized areflexia, pes cavus, and slowing on MNCVs. Seven X-linked restriction fragment length polymorphisms mapping in the Xp11-q21 region were tested for linkage against CMT. Two-point linkage results showed the highest lod scores with PGK1, DXS159, and DXYS1. Multipoint linkage analysis excluded the CMT gene from being telomeric to either DXS14 or DXYS1, with over 1,000:1 odds. The highest location scores were at PGK1 and 1 cM proximal to DXS159.

X-linked recessive Charcot-Marie-Tooth neuropathy: clinical and genetic study.

We describe three families with X-linked recessive Charcot-Marie-Tooth (CMT) neuropathies. The disease phenotype in family 1 was characterized by infantile onset, weakness of lower legs, areflexia, pes cavus, and mental retardation (2 of 5 patients). The disease phenotype in families 2 and 3 was characterized by late onset, distal weakness, and normal intelligence. Hereditary spastic paraparesis was also present in the CMT patients of family 2. Thirty X-linked DNA markers were used for linkage studies. A maximum lod score of +3.48 was obtained by multipoint linkage analysis for the DXS16 locus mapped at Xp22.2 in family 1. In families 2 and 3, there was suggestion of linkage of Xq26 markers; the peak multipoint lod score for these 2 CMT families was 1.81, at DXS144. These results were suggestive of heterogeneity. The joint analysis including both regions (Xp22.2 and Xq26) provided evidence against homogeneity (chi 2 = 9.12, P less than 0.005).

Charcot-Marie-Tooth neuropathy related to chromosome 1.

One family with documented male-to-male transmission of Charcot-Marie-Tooth (CMT) neuropathy was studied clinically and by genetic linkage. Patients had progressive distal weakness and atrophy, areflexia, and distal sensory loss, but early onset (before age 3 years) in all 5 cases, and phrenic nerve involvement in the propositus (a 39-year-old woman) requiring CPAP ventilator support during the night. Motor-nerve conduction velocities (MNCVs) were significantly slow, consistent with severe demyelinating neuropathy. Electromyography (EMG) data were normal. Two-point and multipoint linkage analyses strongly suggested the presence of a CMT gene on chromosome 1q. A maximum multipoint lod score of 2.70 was obtained at MUC1 (theta = 0), with the locus order centromere-MUC1-SPTA1-Fc gamma RII-AT3-telomere. Multipoint linkage analysis excluded the CMT locus from chromosome 17 markers in this family.

Heterogeneity in X-linked recessive Charcot-Marie-Tooth neuropathy.

Three families presenting with X-linked recessive Charcot-Marie-Tooth neuropathies (CMT) were studied both clinically and genetically. The disease phenotype in family 1 was typical of CMT type 1, except for an infantile onset; two of five affected individuals were mentally retarded, and obligate-carrier females were unaffected. Families 2 and 3 showed distal atrophy with weakness, juvenile onset, and normal intelligence. Motor-nerve conduction velocities were significantly slowed, and electromyography data were consistent with denervation in affected CMT males in all three families. Thirty X-linked RFLPs were tested for linkage studies against the CMT disease loci. Family 1 showed tight linkage (recombination fraction [theta] = 0) to Xp22.2 markers DXS16, DXS143, and DXS43, with peak lod scores of 1.75, 1.78, and 2.04, respectively. A maximum lod score of 3.48 at DXS16 (theta = 0) was obtained by multipoint linkage analysis of the map DXS143-DXS16-DXS43. In families 2 and 3 there was suggestion of tight linkage (theta = 0) to Xq26 markers DXS86, DXS144, and DXS105, with peak lod scores of 2.29, 1.33, and 2.32, respectively. The combined maximum multipoint lod score of 1.81 at DXS144 (theta = 0) for these two families occurred in the map DXS10-DXS144-DXS51-DXS105-DXS15-DXS52++ +. A joint homogeneity analysis including both regions (Xp22.2 and Xq26-28) provided evidence against homogeneity (chi 2 = 9.12, P less than .005). No linkage to Xp11.12-q22 markers was observed, as was reported for X-linked dominant CMT and the Cowchock CMT variant. Also, the chromosomes 1 and 17 CMT loci were excluded by pairwise linkage analysis in all three families.

Manifesting carrier of Becker muscular dystrophy (BMD): clinical and recombinant DNA studies.

We studied a Becker muscular dystrophy (BMD) family with a manifesting carrier. Proximal muscle weakness, pseudohypertrophy of the calves, significantly elevated serum creatine kinase and dystrophic alterations in the muscle biopsy were the characteristic phenotypical features of this manifesting carrier. The recombinant DNA study showed a recombinant chromosome with a crossover between pERT 87-8 and pERT J-Bir in the manifesting carrier. However, the proximal part of the short arm of her X chromosome was identical to a non-manifesting carrier (her sister) and to her affected brother. For this reason, we assumed the BMD mutation was proximal to the crossover. The dystrophin cDNA probes showed no deletion of DMD/BMD gene.

Duchenne muscular dystrophy in monozygotic twins: deletion of 5' fragments of the gene.

A recombinant DNA study for deletion evaluation was performed in a 4 generation family with Duchenne muscular dystrophy (DMD) in twins. The patients were 6 years old, had a history of progressive difficulty in walking since age 4, and showed weak gluteals, iliopsoas, latissimus dorsi, rhomboids, lower trapezius, sternocleidomastoids, pseudohypertrophic calves, and tight heelcords. Both patients had high serum creatine kinase of 19,000 and 11,000 IU, respectively, and the muscle biopsy of the left vastus lateralis showed dystrophic alterations. Both twins had the same red cell types for ABO, Rh, CDE, MNSs, Kelly, Lewis, Duffy, and Kidd. HLA typing also detected the same antigens in both twins: A2, B44, DR4, and DR5. Cytogenetic studies were consistent with 46, XY male individuals with normal banding pattern. By cDNA probes the entire DMD gene was surveyed for missing or abnormal-sized restriction fragments. Both twin boys showed absence of 8.5, 8.0, 4.6, 4.2, and 3.1 kb fragments on Hind III blots and absence of 13.5, 3.7, 2.9, and 1.4 kb fragments on Bgl II blots both hybridized with cDNA 1-2a corresponding to most 5' region of the DMD gene. The mother and other relatives of the patient did not show deletion. These findings strongly suggest that the deletion in the DMD monozygotic twins represents a new mutation.

X-linked dominant Charcot-Marie-Tooth neuropathy with 15 cases in a family genetic linkage study.

A large CMT family with 5 affected males and 10 affected females of 37 members in four generations was investigated by recombinant DNA studies. The proband patient in his original description of the pedigree indicated male-to- male transmission in one of his relatives, suggesting autosomal dominant inheritance. The genetic linkage study between the CMT locus and the loci of six markers mapped on chromosome 1 (FY, APCS, AT3, REN, APOA2, and GBA) gave negative results. These findings prompted further pedigree investigation which proved that male-to-male transmission was not present. A genetic linkage study with DXYS1, which is a DNA marker mapped on the long arm of the chromosome X, revealed tight linkage with z = 3.15 at theta = 0.10.

Recombinant DNA study of Duchenne muscular dystrophy occurring in a myotonic dystrophy family.

A recombinant DNA study was performed in a three-generation family with 8 typical cases of late onset myotonic dystrophy (DM) and with one case of Duchenne muscular dystrophy (DMD). The study with DNA markers for chromosome 19 showed linkage of DM locus to the 3.8 Kb allele of apolipoprotein C2 (APOC2) probe and to 9 Kb allele of pSC11 probe (APOC2 lod score = 0.69 at theta = 0). The 21-year-old DMD patient showed no myotonic signs. His clinical history revealed onset with weakness around 4 years of age, progressive course with wheelchair confinement at 11, and cardiomyopathy. His karyotype was normal (46, XY). The study with 10 DNA markers for the chromosome X found a deletion limited to XJ 1.1, XJ 1.2, and XJ 2.3 probes. His 22-year-old sister with typical clinical, EMG and recombinant DNA findings characteristic for myotonic dystrophy was also a carrier of DMD deletion.

Becker muscular dystrophy recombinant DNA studies in identical twins.

Two identical twins with Becker Muscular Dystrophy are reported. Both twins had the same red cell types for ABO, Rh, CDE, MNSs, Kelly, Lewis, Duffy, and Kidd. HLA typing detected the same antigens in both twins: A1, A26, B8, B17, DR3, DR7. Family history was negative. The twin patients showed identical haplotypes that were different from the haplotypes of the normal male members of the family. The sister of the twins showed a recombinant X chromosome. The informative haplotype with respect to the gene of BMD, present in the twins, was ascertained in their mother as well. Our findings strongly suggest that a mutation has occurred either in the mother or in the twins.