The Charcot–Marie–Tooth Binary Repeat Contains a Gene Transcribed from the Opposite Strand of a Partially Duplicated Region of theCOX10Gene

Abstract

Misalignment between the two elements of the CMT1A-REP binary repeat on chromosome 17p11.2–p12 causes two inherited peripheral neuropathies, Charcot–Marie–Tooth type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies. This binary repeat contains repetitive DNA elements that include LINES, SINES, medium reiteration frequency repeats, and a transposon-like element. TheCOX10gene has been mapped 10 kb centromeric to the distal CMT1A-REP element, and a portion of this gene is present in both the proximal and the distal CMT1A-REP elements. We report the isolation and characterization of a novel cDNA (C170RF1), which maps centromeric to and partially within the proximal CMT1A-REP element. Part of C170RF1 is transcribed from the opposite strand of theCOX10partial gene duplication present in the proximal CMT1A-REP element. This finding shows that C170RF1 andCOX10are being transcribed from opposite strands of identical DNA sequences that are separated by 1.5 Mb in the genome. RT-PCR analysis showed the proximal transcript was expressed in skeletal muscle. Sequence analysis identified an open reading frame encoding a 199-amino-acid protein. Zoo blot analysis showed that the transcript is conserved in nonhuman primates. The presence of a binary repeat contributes to the instability of this region of chromosome 17, yet two CMT1A-REP elements are present in the chimpanzee and all human populations. The presence of expressed sequences in both elements of the CMT1A-REP binary repeat could explain the maintenance of this repeat in humans.