Decoding the genetics of synaesthesia using state-of-the-art genomics

It was first noted over a century ago that synaesthesia runs in families. This familial clustering suggests that genetic factors play an important role in an individual's likelihood of developing synaesthesia. However, specific genetic variants that predispose to synaesthesia have yet to be discovered. Furthermore, the genetic architecture is likely to be complex and to vary among individuals. We are taking advantage of the latest advances in DNA technology to investigate the genetic basis of synaesthesia from a genomic perspective. In one approach, known as exome sequencing, we screen the protein‐coding parts of the genome in families containing multiple people with synaesthesia. This strategy promises to uncover rare genetic variants that are shared by affected relatives, and which may therefore contribute to synaesthesia in these families. In another approach, we collect DNA samples from a large number of unrelated synaesthetes, and compare them with control samples to assess whether common genetic variants are associated with synaesthesia. Our current set of cases allows for testing of candidate genetic variants arising from particular neurobiological hypotheses. Through ongoing international collaborations we aim to obtain a sufficiently large sample for a genome‐wide association screen, in which we analyse many thousands of variants across all chromosomes. Findings from these complementary approaches will be integrated to assess whether they converge on shared biological pathways. Identifying genetic variants that underlie synaesthetic experiences will not only shed light on the molecular basis of synaesthesia, but may also contribute to our understanding of neural connectivity in the developing brain.