Abstract
Autosomal recessive mutations in the GJA12/GJC2 gene encoding the gap junction protein connexin47 (C × 47) cause a form of Pelizaeus–Merzbacher-like disease (PMLD) with hypomyelination, nystagmus, impaired psychomotor development and progressive spasticity. We investigated the functional consequences of four C × 47 missense mutations (G149S, G236R, T265A, and T398I) and one C × 47 complex mutation (A98G_V99insT) by immunoblot analysis and immunocytochemistry in transfected communication-incompetent HeLa cells and in OLI-neu cells. All studied C × 47 mutants, except G236R, generated stable proteins in transfected HeLa cells and OLI-neu cells. The mutants T265A and A98G_V99insT were retained in the ER, T398I formed gap junctional plaques at the plasma membrane, and G149S showed both, structures at the plasma membrane and ER localization. Two-microelectrode voltage clamp analyses in Xenopus laevis oocytes injected with wild-type and mutant C × 47 cRNA revealed reduced hemichannel currents for G236R, T265A, and A98G_V99insT. In contrast, T398I revealed hemichannel currents comparable to wild-type. For C × 47 mutant T398I, our results indicate a defect in hemichannel function, whereas C × 47 mutants G149S, G236R, T265A, and A98G_V99insT are predicted to result in a loss of C × 47 hemichannel function. Thus, PMLD is likely to be caused by two different disease mechanisms: a loss of function and a dysfunction.
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Acknowledgements
We thank J Kaiser and I Markmann for technical assistance and H Werner and P De Monasterio for providing OLI-neu cells. This study was supported by the Deutsche Forschungsgemeinschaft grant number GA354/6-1 (to JG and MH).
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Diekmann, S., Henneke, M., Burckhardt, B. et al. Pelizaeus–Merzbacher-like disease is caused not only by a loss of connexin47 function but also by a hemichannel dysfunction. Eur J Hum Genet 18, 985–992 (2010). https://doi.org/10.1038/ejhg.2010.61
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DOI: https://doi.org/10.1038/ejhg.2010.61
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