P̲roline-r̲ich m̲embrane a̲nchor (PRiMA) is responsible for organizing acetylcholinesterase (AChE) into membrane-bound tetrameric form (G₄) in brain and muscles. In avian, G₄ AChE is preferentially expressed in slow-twitch but not in fast-twitch muscles. It is speculated that the expression pattern of PRiMA between the two muscle fiber-types is responsible for this observation. In rodents, two PRiMA splicing variants namely PRiMA I and PRiMA II are present. Their differences in C-termini suggest that they may have distinct functions. However, PRiMA II has not been identified in chicken. Here, we aimed to identify PRiMA II in chicken muscles and to investigate whether the two PRiMA variants exhibited muscle fiber-type specific expression. In addition to the analysis in muscles, the profi...[ Read more ]

P̲roline-r̲ich m̲embrane a̲nchor (PRiMA) is responsible for organizing acetylcholinesterase (AChE) into membrane-bound tetrameric form (G₄) in brain and muscles. In avian, G₄ AChE is preferentially expressed in slow-twitch but not in fast-twitch muscles. It is speculated that the expression pattern of PRiMA between the two muscle fiber-types is responsible for this observation. In rodents, two PRiMA splicing variants namely PRiMA I and PRiMA II are present. Their differences in C-termini suggest that they may have distinct functions. However, PRiMA II has not been identified in chicken. Here, we aimed to identify PRiMA II in chicken muscles and to investigate whether the two PRiMA variants exhibited muscle fiber-type specific expression. In addition to the analysis in muscles, the profiling of G₄ AChE and PRiMA were also revealed in other tissues.

By RT-PCR, two splicing variants of PRiMA were identified in chicken cerebrum. Sequencing and bioinformatics analyses showed that one splicing variant contained exon 1, 2, 3, and 4 while the other one possessed exon 1, 2, 3, 3b and 4. The splicing patterns of the two variants in chicken were resembled to PRiMA I and II in rodents. By quantitative PCR analysis, the expression of PRiMA I and II were higher in slow-twitch muscle than in fast-twitch muscle of chicken. These results suggested that the muscle fiber type-specific expression of G₄ AChE might be attributed to the differential expression pattern of PRiMA. Regarding to the tissue distribution, the two PRiMA isoforms and G₄ AChE were widely expressed in different tissues.

In summary, a novel PRiMA II isoform was identified in chicken. The differential expression pattern of PRiMA mRNAs in fast-twitch and slow-twitch muscles contributed to the expression profile of G₄ AChE. Finally, the revealing of PRiMA-linked G₄ AChE in tissues other than brain and muscle suggested a non-cholinergic role in different systems.