Chromosome loci vary by juvenile myoclonic epilepsy subsyndromes: linkage and haplotype analysis applied to epilepsy and EEG 3.5–6.0 Hz polyspike waves

Abstract

Juvenile myoclonic epilepsy (JME), the most common genetic epilepsy, remains enigmatic because it is considered one disease instead of several diseases. We ascertained three large multigenerational/multiplex JME pedigrees from Honduras with differing JME subsyndromes, including Childhood Absence Epilepsy evolving to JME (CAE/JME; pedigree 1), JME with adolescent onset pyknoleptic absence (JME/pA; pedigree 2), and classic JME (cJME; pedigree 3). All phenotypes were validated, including symptomatic persons with various epilepsies, asymptomatic persons with EEG 3.5–6.0 Hz polyspike waves, and asymptomatic persons with normal EEGs. Two‐point parametric linkage analyses were performed with 5185 single‐nucleotide polymorphisms on individual pedigrees and pooled pedigrees using four diagnostic models based on epilepsy/EEG diagnoses. Haplotype analyses of the entire genome were also performed for each individual. In pedigree 1, haplotyping identified a 34 cM region in 2q21.2–q31.1 cosegregating with all affected members, an area close to 2q14.3 identified by linkage (Z max = 1.77; pedigree 1). In pedigree 2, linkage and haplotyping identified a 44 cM cosegregating region in 13q13.3–q31.2 (Z max = 3.50 at 13q31.1; pooled pedigrees). In pedigree 3, haplotyping identified a 6 cM cosegregating region in 17q12. Possible cosegregation was also identified in 13q14.2 and 1q32 in pedigree 3, although this could not be definitively confirmed due to the presence of uninformative markers in key individuals. Differing chromosome regions identified in specific JME subsyndromes may contain separate JME disease‐causing genes, favoring the concept of JME as several distinct diseases. Whole‐exome sequencing will likely identify a CAE/JME gene in 2q21.2–2q31.1, a JME/pA gene in 13q13.3–q31.2, and a cJME gene in 17q12.

Genome‐wide association studies of alcohol dependence, DSM‐IV criterion count and individual criteria

“…58 The chromosome 2 region is in a gene desert ( Figure S4B) and has been linked to cognitive test scores, 59 attention-deficit/hyperactivity disorder (ADHD) symptom count, 60 ADHD, 61 current smoking 62 and juvenile myoclonic epilepsy. 63 The region on chromosome 8 has been linked to bipolar disorder. 64 The only gene near the chromosome 8 region is FAM84B ( Figure S4D), however, this gene does not seem to be related to any neuropsychiatric diseases.…”