Transcript Analysis of Zebrafish GLUT3 Genes, and , Define Overlapping as Well as Distinct Expression Domains in the Zebrafish () Central Nervous System.

The transport of glucose across the cell plasma membrane is vital to most mammalian cells. The glucose transporter (GLUT; also called SLC2A) family of transmembrane solute carriers is responsible for this function . GLUT proteins encompass 14 different isoforms in humans with different cell type-specific expression patterns and activities. Central to glucose utilization and delivery in the brain is the neuronally expressed GLUT3. Recent research has shown an involvement of GLUT3 genetic variation or altered expression in several different brain disorders, including Huntington's and Alzheimer's diseases. Furthermore, was identified as a potential risk gene for multiple psychiatric disorders. To study the role of GLUT3 in brain function and disease a more detailed knowledge of its expression in model organisms is needed. Zebrafish () has in recent years gained popularity as a model organism for brain research and is now well-established for modeling psychiatric disorders. Here, we have analyzed the sequence of GLUT3 orthologs and identified two paralogous genes in the zebrafish, and . Interestingly, the Glut3b protein sequence contains a unique stretch of amino acids, which may be important for functional regulation. The transcript is detectable in the central nervous system including distinct cellular populations in telencephalon, diencephalon, mesencephalon and rhombencephalon at embryonic and larval stages. Conversely, the transcript shows a rather diffuse expression pattern at different embryonic stages and brain regions. Expression of is maintained in the adult brain and is found in the telencephalon, diencephalon, mesencephalon, cerebellum and medulla oblongata. The transcripts are present in overlapping as well as distinct regions compared to . Double hybridizations were used to demonstrate that is expressed by some GABAergic neurons at embryonic stages. This detailed description of zebrafish and expression at developmental and adult stages paves the way for further investigations of normal GLUT3 function and its role in brain disorders.