The cellular and subcellular localization of zinc transporter 7 in the mouse spinal cord

The present work addresses the cellular and subcellular localization of the zinc transporter 7 (ZNT7, SLC30a7) protein and the distribution of zinc ions (Zn2+) in the mouse spinal cord. Our results indicated that the ZNT7 immunoreactive neurons were widely distributed in the Rexed's laminae of the gray matter in all spinal segments examined. The ependyma cells of the central canal and glia cells in the white matter were also shown ZNT7-positive. The ZNT7 immunoreactivity was mainly detected in the perinuclear regions of ZNT7-positive cells in the spinal gray matter. For ependyma cells, the immunoreactivity of ZNT7 was detected in the cytoplasm near the lumina of the central canal. Ultrastructural localization showed that ZNT7 was predominately present in the membrane of the Golgi stacks. The double immunofluorescence studies confirmed this result. Other intracellular organelles including the endoplasmic reticulum, mitochondria and lysosomes were devoid of ZNT7-immunostaining. The chelatable Zn2+ ions in the spinal cord were found predominantly in the terminals of the neuron rather than the cell body in the gray matter. However, overlapping distribution of chelatable Zn2+ ions and ZNT7 was found in the ependyma cells. The present study supports the notion that ZNT7 may function to supply zinc ions to the newly synthesized metalloproteins in the secretory pathway of the spinal neuron and the ependyma cell.