Zn(2+) is required for many aspects of neuronal structure and function. However, the regulation of Zn(2+) in the nervous system remains poorly understood. Systematic analysis of tissue-profiling microarray data showed that the zinc transporter ZIP12 (slc39a12) is highly expressed in the human brain. In the work reported here, we confirmed that ZIP12 is a Zn(2+) uptake transporter with a conserved pattern of high expression in the mouse and Xenopus nervous system. Mouse neurons and Neuro-2a cells produce fewer and shorter neurites after ZIP12 knockdown without affecting cell viability. Zn(2+) chelation or loading in cells to alter Zn(2+) availability respectively mimicked or reduced the effects of ZIP12 knockdown on neurite outgrowth. ZIP12 knockdown reduces cAMP response element-binding protein activation and phosphorylation at serine 133, which is a critical pathway for neuronal differentiation. Constitutive cAMP response element-binding protein activation restores impairments in neurite outgrowth caused by Zn(2+) chelation or ZIP12 knockdown. ZIP12 knockdown also reduces tubulin polymerization and increases sensitivity to nocodazole following neurite outgrowth. We find that ZIP12 is expressed during neurulation and early nervous system development in Xenopus tropicalis, where ZIP12 antisense morpholino knockdown impairs neural tube closure and arrests development during neurulation with concomitant reduction in tubulin polymerization in the neural plate. This study identifies a Zn(2+) transporter that is specifically required for nervous system development and provides tangible links between Zn(2+), neurulation, and neuronal differentiation.
PubMed ID: 23716681
PMC ID: PMC3683776
Article link: Proc Natl Acad Sci U S A.
Grant support: P30 GM092374 NIGMS NIH HHS , P40 OD010997 NIH HHS , P40 OD010997 NIH HHS , P41 RR001395S1 NCRR NIH HHS
Genes referenced: ctnnb1 gapdh slc39a12
Morpholinos referenced: slc39a12 MO1 slc39a12 MO2
Article Images: [+] show captions
|Fig. 5. ZIP12 is expressed primarily in the neural tube and brain of X. tropicalis and is required for neural tube closure and embryonic viability. (A and B) ZIP12 and β-actin or GAPDH expression was determined in various adult tissues and developmental stages by RT-PCR. (C) ZIP12 mRNA expression is elevated in the neural plate, as determined by quantitative RT-PCR (n = 6, +/- SE). ***P < 0.001 versus whole embryo; ###P < 0.001 versus rest of embryo. (D) ZIP12 mRNA (slc39a12) is expressed during neurulation and early nervous system development, analyzed by in situ hybridization. (E-M) ZIP12 knockdown by antisense morpholino microinjection impairs X. tropicalis development during neurulation. (N) Microinjection of slc39a12MO1 does not affect tubulin protein content, analyzed by immunoblotting. (O) Microinjection of slc39a12MO1 affects the ratio of polymerized to soluble β2-tubulin, as analyzed by polymerized tubulin fractionation and immunoblotting. (Scale bars: 250 μm in all images.)|
|scl39a12 (solute carrier family 39 (zinc transporter), member 12) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 17, dorsal view, anterior up.|
|scl39a12 (solute carrier family 39 (zinc transporter), member 12) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 28, lateral view, anterior left, dorsal up (top and bottom left panel), dorsal view of head, anterior down (bottom right view).|
|scl39a12 (solute carrier family 39 (zinc transporter), member 12) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 40, lateral view, anterior left, dorsal up ( top and bottom left panel), dorsal view of head, anterior down ( bottom right view).|