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J Biol Chem June 10, 2016; 291 (24): 12601-11.

Two Different Functions of Connexin43 Confer Two Different Bone Phenotypes in Zebrafish.

Misu A , Yamanaka H , Aramaki T , Kondo S , Skerrett IM , Iovine MK , Watanabe M .

Fish remain nearly the same shape as they grow, but there are two different modes of bone growth. Bones in the tail fin (fin ray segments) are added distally at the tips of the fins and do not elongate once produced. On the other hand, vertebrae enlarge in proportion to body growth. To elucidate how bone growth is controlled, we investigated a zebrafish mutant, steopsel (stp(tl28d)). Vertebrae of stp(tl28d) (/+) fish look normal in larvae (∼30 days) but are distinctly shorter (59-81%) than vertebrae of wild type fish in adults. In contrast, the lengths of fin rays are only slightly shorter (∼95%) than those of the wild type in both larvae and adults. Positional cloning revealed that stp encodes Connexin43 (Cx43), a connexin that functions as a gap junction and hemichannel. Interestingly, cx43 was also identified as the gene causing the short-of-fin (sof) phenotype, in which the fin ray segments are shorter but the vertebrae are normal. To identify the cause of this difference between the alleles, we expressed Cx43 exogenously in Xenopus oocytes and performed electrophysiological analysis of the mutant proteins. Gap junction coupling induced by Cx43(stp) or Cx43(sof) was reduced compared with Cx43-WT. On the other hand, only Cx43(stp) induced abnormally high (50× wild type) transmembrane currents through hemichannels. Our results suggest that Cx43 plays critical and diverse roles in zebrafish bone growth.

PubMed ID: 27129238
PMC ID: PMC4933477
Article link: J Biol Chem

Species referenced: Xenopus laevis
Genes referenced: gja1 sult1a1

References [+] :
Abascal, Evolutionary analyses of gap junction protein families. 2012, Pubmed