The genetic landscape of axonal neuropathies in the middle-aged and elderly: Focus on MME

Neurology. 2020 Dec 15;95(24):e3163-e3179. doi: 10.1212/WNL.0000000000011132. Epub 2020 Nov 3.

Abstract

Objective: To test the hypothesis that monogenic neuropathies such as Charcot-Marie-Tooth disease (CMT) contribute to frequent but often unexplained neuropathies in the elderly, we performed genetic analysis of 230 patients with unexplained axonal neuropathies and disease onset ≥35 years.

Methods: We recruited patients, collected clinical data, and conducted whole-exome sequencing (WES; n = 126) and MME single-gene sequencing (n = 104). We further queried WES repositories for MME variants and measured blood levels of the MME-encoded protein neprilysin.

Results: In the WES cohort, the overall detection rate for assumed disease-causing variants in genes for CMT or other conditions associated with neuropathies was 18.3% (familial cases 26.4%, apparently sporadic cases 12.3%). MME was most frequently involved and accounted for 34.8% of genetically solved cases. The relevance of MME for late-onset neuropathies was further supported by detection of a comparable proportion of cases in an independent patient sample, preponderance of MME variants among patients compared to population frequencies, retrieval of additional late-onset neuropathy patients with MME variants from WES repositories, and low neprilysin levels in patients' blood samples. Transmission of MME variants was often consistent with an incompletely penetrant autosomal-dominant trait and less frequently with autosomal-recessive inheritance.

Conclusions: A detectable fraction of unexplained late-onset axonal neuropathies is genetically determined, by variants in either CMT genes or genes involved in other conditions that affect the peripheral nerves and can mimic a CMT phenotype. MME variants can act as completely penetrant recessive alleles but also confer dominantly inherited susceptibility to axonal neuropathies in an aging population.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age of Onset
  • Aged
  • Aging* / blood
  • Charcot-Marie-Tooth Disease / blood
  • Charcot-Marie-Tooth Disease / genetics
  • Female
  • Genetic Predisposition to Disease / genetics
  • Hereditary Sensory and Motor Neuropathy / blood
  • Hereditary Sensory and Motor Neuropathy / genetics*
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Male
  • Middle Aged
  • Neprilysin / blood
  • Neprilysin / genetics*
  • Whole Exome Sequencing

Substances

  • Neprilysin