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The most important genetics news of the year may have been the presentation by Huang and colleagues at the Tourette World Congress in London this June, reporting on a large collaborative study of copy number variants (CNVs) in approximately 2,500 TS cases and 3,500 controls \citep{Huang:London}. They first tested some CNVs previously reported in various neurological and psychiatric illnesses; the most significant confirmation in this sample was of exonic deletions in _NRXN1_, a gene previously implicated in autism and TS \citep*{24578685}. They also searched for new, large CNVs and identified a novel TS locus, _CNTN6_, that was significant at a whole-genome level by permutation testing. This gene and 4 of the 32 next most likely candidates this analysis identified are neural adhesion molecules \citep*{24578685}. _CNTN6_ is a reasonable candidate for etiologically contributing to TS; its expression in the brain varies during development \citep{18046458}, knockout mice show motor deficits \citep{12884264}, and an independent study found a variety of neurological and psychiatric symptoms (including 2 with OCD) in 14 patients identified by _CNTN6_ CNVs \citep{26257835}. On the other hand, fewer than 1% of TS cases in this sample had CNVs in _CNTN6_, so its overall importance in TS remains to be more fully characterized.  A large collaborative group studied _AADAC_, the gene encoding arylacetamide deacetylase, in which microdeletions had been identified in a previous, smaller copy number variation study \citep{26444075}. The authors provide evidence from several sources supporting the connection of _AADAC_ and TS, including new patients with _AADAC_ deletions, a significant overall association, and evidence that _AADAC_ is expressed in the brain, though most strongly in cerebellum, hippocampus and olfactory bulb. bulb, rather than the basal ganglia, suggesting that the neural networks associated with tic generation are complex.  A collaborative genetic study \citep{25735483} demonstrated an association of TS with 33 genes related to glycolysis or glutamine metabolism. None of the individual genes would have survived correction for multiple testing and the results were consistent with a combined effect of many genetic variants of small effect. These results narrow the hunt for genes that may contribute to the development of TS and they also suggest a new direction for future electrophysiological, imaging and pharmacological studies.   \citet{25158072} reported a genome-wide association study (GWAS) from 1,310 people with OCD, 834 with Tourette syndrome, 579 with both OCD and a chronic tic disorder, and over 5,500 controls matched for ancestry. A significant polygenic component was identified for OCD without tics, but not for the combined patient group or other subgroups. Overall, this study is consistent with previous work but provided disappointingly few novel results.  An international study examined tic symptoms in the United States and the Netherlands \cite{25714449}. \citep{25714449}.  Three factors were identified: complex vocal tics and obscene behavior, body tics and head/neck tics. Heritability was considered moderate for the first and third factors, h2r=0.21 and 0.25 respectively. Heritability for narrower tic phenotypes is considerably lower than the heritability estimates for frequently comorbid conditions such as OCD and ADHD for which heritability estimates of up to 0.65 have been obtained. ### Environmental risk factors