0026 Strong Gene-Environment Interactions of Trank1 Gene Polymorphisms with Birth Difficulties in Kleine Levin Syndrome

Introduction

Kleine-Levin Syndrome (KLS) is a rare disorder affecting adolescents and characterized by relapsing-remitting episodes of severe hypersomnia, cognitive impairment, and behavioral disturbances such as hyperphagia and sexual disinhibition. Pathophysiology is unknown, although imaging studies indicate decreased activity in hypothalamic/thalamic areas and in cortical areas during episodes. Familial occurrence is increased, and risk is associated with reports of complicated birth.

Methods

A worldwide Genome wide association (GWA) study was conducted in 673 KLS patients and ethnically matched 15,341 control individuals.

Results

We found a strong genome-wide significant association (OR=1.48 at rs150168018, p=8.6x10-9) with 24 single nucleotide polymorphisms (SNPs) encompassing a 35kb region located in the 5’ region of TRANK1 gene previously associated with bipolar disorder and schizophrenia. Strikingly, KLS cases with TRANK1 had statistically increased reports of difficult birth. As perinatal outcomes have dramatically improved over the last 40 years, we further stratified our sample by birth years, and found that recent cases had a significantly reduced TRANK1 association. These findings were confirmed in an independent replication cohort of 171 new patients where polygenic risk scores constructed on the discovery cohort replicated (r2=0.15; p<2.7x10-22 at p=0.1 threshold) and the TRANK1 association was found to be dependent on reports of birth difficulties (OR=1.54, p=0.01 versus OR=1.12, p=0.4). Pathway analysis of the overall GWAS association revealed significant association (p=0.02) with 19 genes in a pathway modulating rhythmic behaviors.

Conclusion

Our results demonstrate links between hypersomnia, behavioral rhythmicity and bipolar disorder and indicate that a polymorphism in the TRANK1 region affect brain development in the presence of a perinatal injury, with pathophysiological consequences such as KLS, bipolar disorder and schizophrenia.

Support

NIH NIMH 1R01MH080957 to EM PHRC 070138 to IA