Chicken GLUT4 undergoes complex alternative splicing events and its expression in striated muscle changes dramatically during development

Glucose transporter protein 4 (GLUT4) plays an important role in regulating insu- lin-mediated glucose homeostasis in mammals. Until now, studies on GLUT4 have focused on mammals mostly, while chicken GLUT4 has been rarely investi- gated. In this study, chicken GLUT4 mRNA sequences were obtained by combining conventional amplifica- tion, 5'-and 3'-rapid amplification of cDNA ends tech- nique (RACE), then bioinformatics analysis on its genomic structure, splicing pattern, subcellular locali- zation prediction and homologous comparisons were carried out. In addition, the distribution of GLUT4 was detected by RT-qPCR in bird's liver and striated muscles (cardiac muscle, pectoralis and leg muscle) at different ages, including embryonic day 14 (E14), E19, 7-day-old (D7), D21 and D49 (n=3-4). Results showed that chicken GLUT4 gene produced at least 14 transcripts (GenBank accession No: OP491293- OP491306) through alternative splicing and polyadeny- lation, which predicted encoding 12 types of amino acid (AA) sequences (with length ranged from 65 AA to 519 AA). These proteins contain typical major facilitator superfamily domain of glucose transporters with length variations, sharing a common sequence of 59 AA, and were predicted to have distinct subcellular localization. The dominant transcript (named as T1) consists of 11 exons with an open reading frame being predicted encoding 519 AA. In addition, analyzing on the spatio- temporal expression of chicken GLUT4 showed it domi- nantly expressed in pectoralis, leg muscles and cardiac muscle, and the mRNA level of chicken GLUT4 dra- matically fluctuated with birds' development in cardiac muscle, pectoralis and leg muscles, with the level at D21 significantly higher than that at E14, E19, and D49 (P < 0.05). These data indicated that chicken GLUT4 undergoes complex alternative splicing events, and GLUT4 expression level in striated muscle was sub- jected to dynamic regulation with birds' development. Results indicate these isoforms may play overlapping and distinct roles in chicken.

Automated summary

This study obtained chicken GLUT4 mRNA sequences and conducted bioinformatics analysis on its genomic structure, splicing pattern, subcellular localization prediction and homologous comparisons. RT-qPCR detection showed that chicken GLUT4 is distributed in bird's liver and striated muscles, and at least 14 transcripts encoding 12 types of amino acid sequences were produced through alternative splicing and polyadenylation. These isoforms may play overlapping and distinct roles in chicken during development.