MEIS1 intronic risk haplotype associated with restless legs syndrome affects its mRNA and protein expression levels.
Restless legs syndrome (RLS) is a common neurological disorder characterized by an irresistible urge to move the legs at night, which is often accompanied by unpleasant sensations. A recent genomewide association study identified an association between RLS and intronic markers from the MEIS1 gene. Comparative genomic analysis indicates that MEIS1 is the only gene encompassed in this evolutionarily conserved chromosomal segment, i.e. a conservation synteny block, from mammals to fish. We carried out a series of experiments to delineate the role of MEIS1 in RLS pathogenesis and the underlying genetic mechanism. We sequenced all 13 MEIS1 exons and their splice junctions in 285 RLS probands with confirmed clinical diagnosis and did not identify any causative coding or exon-intron junction mutations. We found no evidence of structural variation or disease-associated haplotype differential splicing. However, sequencing of conserved regions of MEIS1 introns 8 and 9 identified a novel single nucleotide polymorphism (C13B_2) significantly associated with RLS (allelic association, P = 1.81E-07). We detected a significant decrease in MEIS1 mRNA expression by quantitative real-time polymerase chain reaction in lymphoblastoid cell lines (LCLs) and brain tissues from RLS patients homozygous for the intronic RLS risk haplotype, compared with those homozygous for the non-risk haplotype. Finally, we found significantly decreased MEIS1 protein levels in the same batch of LCLs and brain tissues from the homozygous carriers of the risk haplotype, compared with the homozygous non-carriers. Therefore, these data suggest that reduced expression of the MEIS1 gene, possibly through intronic cis-regulatory element(s), predisposes to RLS.
Xiong
Lan
L
Centre of Excellence in Neuromics of University of Montreal, CHUM Research Center, University of Montreal, Montréal, Québec, Canada.
Catoire
Hélène
H
Dion
Patrick
P
Gaspar
Claudia
C
Lafrenière
Ronald G
RG
Girard
Simon L
SL
Levchenko
Anastasia
A
Rivière
Jean-Baptiste
JB
Fiori
Laura
L
St-Onge
Judith
J
Bachand
Isabelle
I
Thibodeau
Pascale
P
Allen
Richard
R
Earley
Christopher
C
Turecki
Gustavo
G
Montplaisir
Jacques
J
Rouleau
Guy A
GA
D017398:Alternative Splicing / Q000235:genetics; D001921:Brain / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics*; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D020161:Physical Chromosome Mapping; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012148:Restless Legs Syndrome / Q000235:genetics*
D018398:Homeodomain Proteins; C000616391:MEIS1 protein, human; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger