Jeremy Laurance in The Independent says that a study led by Hugh Gurling has opened up the prospect of so-called personalised treatment of bipolar disorder with drugs targeting the metabotropic glutamate receptor 3 (mGluR3). This is based on a finding that the Kozak sequence variant of the glutamate receptor 3 (GRM3) gene, which encodes for mGluR3, was overrepresented in a sample of bipolar disorder cases compared with controls. As the paper concludes, confirmation of this finding is needed before accepting this potential marker. It could just be a chance finding based on screening until a significant result is found.
As the paper also points out, "The GRM3 gene has been investigated in bipolar affective disorder as part of several genome-wide association studies (GWASs) but failed to reach genome-wide significance in any of these investigations." Still research goes on with this gene because it is assumed the failure to find genetic association is "probably the result of the presence of low-frequency disease alleles and the high degree of etiologic genetic heterogeneity". Actually it's more likely that there's no genetic link.
I haven't forgotten Hugh Gurling's false claim in Nature in 1988 that he'd found strong evidence for the involvement of a single gene on chromosome 5 in the causation of schizophrenia. Jeremy Laurance shouldn't be so easily taken in by claims for so-called personalised (actually there's nothing personal about it in the sense of relating to patients) psychiatry.