Distribution of transcripts of the GFOD gene family members gfod1 and gfod2 in the zebrafish central nervous system.

The glucose-fructose oxidoreductase domain containing gene family (GFOD) is small and contains only two members in human (GFOD1 and GFOD2). Information about its function is scarce. As the name implies the proteins contain an enzyme-defining domain, however, if this is functional and has enzymatic activity remains to be shown. A single nucleotide polymorphism situated in an intron of GFOD1 was found to be associated with inattentive symptomology in patients with attention-deficit/hyperactivity disorder. Further, in a large schizophrenia genome-wide association study the GFOD2 locus was found to be associated with the psychiatric condition. Until now, however, it is unclear what specific functions are associated with the two GFOD-family members, if they might be involved in neurodevelopment and how this may relate to the development of psychiatric disorders. In order to gain first insights into the hypothesis that GFOD-family members are involved in brain development and/or function we performed RNA in situ hybridization on zebrafish (Danio rerio) tissues at different developmental stages. We found that both family members are expressed in the central nervous system at embryonic, larvae and adult stages. We were able to define subtle differences of expression of the two gfod genes and we showed that a subset of GABAergic neurons express gfod1. Taken together, we conclude that both gfod gene family members are expressed in overlapping as well as in distinct regions in the zebrafish central nervous system. Our data suggest that gfod1 and gfod2 are relevant both for the developing and adult zebrafish brain. This study paves the way for further functional analyses of this yet unexplored gene family.