Family-Based Analysis Combined with Case-Controls Study Implicate Roles of PCNT in Tourette Syndrome.

OBJECTIVE: Tourette syndrome (TS) is a childhood-onset neuro-developmental disorder and the genetic factors play an important role in its etiology. As pericentrin (PCNT) binds to disruption-in-schizophrenia 1 (DISC1) and is a risk factor for many mental illnesses, we aimed to investigate the effect of PCNT on TS in the Chinese Han population. METHODS: Five tag single nucleotide polymorphisms (SNPs) (rs17371795, rs2839227, rs2839228, rs6518291 and rs9983522) in PCNT were screened in 407 TS nuclear family trios and 506 healthy persons by the TaqMan assays real-time. A common case-control study was designed to recognize differences in the genetic distributions. Additionally, we conducted a family based association study including transmission disequilibrium test, haplotype relative risk, and haplotype-based haplotype relative risk for these SNPs. RESULTS: The allele frequencies revealed a significant difference of rs17371795, rs2839227 and rs2839228 between TS patients and controls (for rs17371795: P=0.002, OR=0.691, 95% CI=0.547-0.874; for rs2839227: P=0.001, OR=0.682, 95% CI=0.540-0.860; for rs2839228: P=0.028, OR=0.775, 95% CI=0.618-0.973) and genotypic distributions showed a positive association only in rs17371795 and rs2839227 (for rs17371795: P=0.010; for rs2839227: P=0.008). Moreover, only rs2839227 remained significant after Bonferroni correction (P<0.01). CONCLUSION: Our study suggested genetic variability at the PCNT locus may be associated with TS risk in the Chinese Han population.

Mutations in ASH1L confer susceptibility to Tourette syndrome.

Tourette syndrome (TS) is a childhood-onset neuropsychiatric disorder characterized by repetitive motor movements and vocal tics. The clinical manifestations of TS are complex and often overlap with other neuropsychiatric disorders. TS is highly heritable; however, the underlying genetic basis and molecular and neuronal mechanisms of TS remain largely unknown. We performed whole-exome sequencing of a hundred trios (probands and their parents) with detailed records of their clinical presentations and identified a risk gene, ASH1L, that was both de novo mutated and associated with TS based on a transmission disequilibrium test. As a replication, we performed follow-up targeted sequencing of ASH1L in additional 524 unrelated TS samples and replicated the association (P value = 0.001). The point mutations in ASH1L cause defects in its enzymatic activity. Therefore, we established a transgenic mouse line and performed an array of anatomical, behavioral, and functional assays to investigate ASH1L function. The Ash1l+/- mice manifested tic-like behaviors and compulsive behaviors that could be rescued by the tic-relieving drug haloperidol. We also found that Ash1l disruption leads to hyper-activation and elevated dopamine-releasing events in the dorsal striatum, all of which could explain the neural mechanisms for the behavioral abnormalities in mice. Taken together, our results provide compelling evidence that ASH1L is a TS risk gene.