In mammals, the expression of collagen-tailed (ColQ) subunit of acetylcholinesterase (AChE) was found to be muscle fibre-type-specific and synapse-specific. ColQ is responsible for the proper assembly, organization and localization of the collagen-tailed AChE at the neuromuscular junction. However, the regulatory mechanism of ColQ expression is still not yet determined. Two ColQ transcripts, ColQ-1 and ColQ-1a, were identified, which were different in their first exons. Genetic analysis showed that the two ColQ promoters, namely pColQ-1 and pColQ-1a, might be involved in driving the expressions of ColQ-1 and ColQ-1a transcripts, respectively. In order to study the molecular mechanisms governing this differential regulation of ColQ, the two promoters of human ColQ were cloned. Both promo...[ Read more ]

In mammals, the expression of collagen-tailed (ColQ) subunit of acetylcholinesterase (AChE) was found to be muscle fibre-type-specific and synapse-specific. ColQ is responsible for the proper assembly, organization and localization of the collagen-tailed AChE at the neuromuscular junction. However, the regulatory mechanism of ColQ expression is still not yet determined. Two ColQ transcripts, ColQ-1 and ColQ-1a, were identified, which were different in their first exons. Genetic analysis showed that the two ColQ promoters, namely pColQ-1 and pColQ-1a, might be involved in driving the expressions of ColQ-1 and ColQ-1a transcripts, respectively. In order to study the molecular mechanisms governing this differential regulation of ColQ, the two promoters of human ColQ were cloned. Both promoters showed high transcriptional activities when transfected into cultured myotubes. During the myogenic differentiation of C2C12 cells, the transcriptional activities of the two ColQ promoters were in parallel to the endogenous ColQ mRNA expression, indicating the integrity of the two promoters. Promoter analysis showed that the two ColQ promoters contained different transcription factor binding sites such as MEF-2 and E-box. By using in vivo intra-muscular DNA injection and in vitro DNA transfection into cultured myotubes, the muscle fibre-type-specific transcriptional activities of the two ColQ promoters were demonstrated. pColQ-1 drove the slow muscle-expressing pattern of ColQ-1 mRNA, while pColQ-1a drove the fast muscle-expressing pattern of ColQ-1a mRNA. Two smaller regions, s̲low u̲pstream r̲egulatory e̲lement (SURE) and f̲ast i̲ntronic r̲egulatory e̲lement (FIRE), were identified in the ColQ promoters, which could be responsible for muscle fibre-type-specific expression of ColQ transcripts. Furthermore, calcineurin and NFAT transcription factor were shown to participate in this differential regulation of ColQ in different muscle fibre-types. In synapse-specific expression of ColQ, g̲rowth-a̲ssociated b̲inding p̲rotein (GABP) was found to up regulate the transcriptional activities of the two ColQ promoters through N-box motifs. The activation of GABP in muscle was shown to be mediated by neuregulin-1 that acted through a m̲itogen-a̲ctivated p̲rotein (MAP) kinase signalling cascade. Furthermore, adenosine 5'-triphosphate (ATP) and cyclic adenosine 3':5'-monophosphate (cAMP) were also found to up regulate and down regulate the expression of ColQ in muscles respectively. Taken together, the expression of ColQ is muscle-specific and synapse-specific, which could be mediated by nerve-derived factors during the formation and the maintenance of the neuromuscular junction.