Myelin protein zero (MPZ) gene mutations in nonduplication type 1 Charcot-Marie-Tooth disease

✍ Scribed by Benjamin B. Roa; Laura E. Warner; Carlos A. Garcia; Donna Russo; Robert Lovelace; Phillip F. Chance; James R. Lupski

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 975 KB
• Volume: 7
• Category: Article
• ISSN: 1059-7794
• DOI: 10.1002/(sici)1098-1004(1996)7:1<36::aid-humu5>3.0.co;2-n

✦ Synopsis

The myelin protein zero gene (MPZ) maps to chromosome lq22-23 and encodes the most abundant peripheral nerve myelin protein. The Po protein functions as a homophilic adhesion molecule in myelin compaction. Mutations in the MPZ gene are associated with the demyelinating peripheral neuropathies Charcot-Marie-Tooth disease type 1B (CMTlB), and the more severe Dejerine-Sottas syndrome (DSS). We have surveyed a cohort of 70 unrelated patients with demyelinating polyneuropathy for additional mutations in the MPZ gene. The 1.5-Mb DNA duplication on chromosome 17p11.2-pl2 associated with CMT type 1A (CMTlA) was not present. By D N A heteroduplex analysis, four base mismatches were detected in three exons of MPZ. Nucleotide sequence analysis identified a de novo mutation in MPZ exon 3 that predicts an Ile( 135)Thr substitution in a family with clinically severe early-onset CMT1, and an exon 3 mutation encoding a Gly( 137)Ser substitution was identified in a second CMTl family. Each predicted amino acid substitution resides in the extracellular domain of the Po protein. Heteroduplex analysis did not detect either base change in 104 unrelated controls, indicating that these substitutions are disease-associated mutations rather than common polymorphisms. In addition, two polymorphic mutations were identified in M P Z exon 5 and exon 6, which do not alter the codons for Gly(200) and Ser(228), respectively. These observations provide further confirmation of the role of MPZ in CMTlB and suggest that MPZ coding region mutations may account for a limited percentage of disease-causing mutations in nonduplication CMTl patients.