Cloning and Expression of Two Isoforms of Guanylate Cyclase C (GC-C) in the European Eel (Anguilla anguilla)

Complementary DNA fragments for two isoforms of particulate guanylate cyclase C (GC-C) were cloned from the intestine of the European eel ( Anguilla anguilla ). Both isoforms exhibited higher nucleotide and amino acid sequence homologies to members of the GC-C family from other species than the related guanylate cyclase A or B (GC-A or GC-B) isoforms from the eel. Northern blots indicated that probes for both isoforms, termed GC-C1 and GC-C2, selectively hybridised to 4.8-kb transcripts in the intestine and the kidney. Expression of the GC-C2 transcript in the intestine was increased by 100% following the transfer of yellow FW-acclimated eels to SW. Likewise developmental maturation of yellow eels into pre-migratory silver eels resulted in a significant increase (60%) in the intestinal expression of GC-C2. No changes in expression of GC-C2 were seen in the kidney under any condition. RT-PCR indicated that the GC-C2 isoform is only expressed in anterior and mid-gut segments in FW-acclimated yellow eels. However, expression is also extended to the posterior gut segment when yellow eels are acclimated to SW or following developmental transformation into silver eels.