Zinc Uptake and Storage During the Formation of the Cerebral Cortex in Mice

The cerebral cortex (or neocortex) is a brain structure formed during embryogenesis. The present study seeks to provide a detailed characterization of the Zn homeostatic mechanisms during cerebral cortex formation and development. To reach that goal, we have combined high-throughput RNA-sequencing analysis of the whole murine genome, X-ray fluorescence nanoimaging (XRF), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and live-cell imaging of dissociated cortical neurons loaded with the Zn fluorescent probe FluoZin-3. The transcriptomic analysis was conducted from mRNAs isolated from cortices collected at embryonic (E) days 11 (E11), E13, and E17 and on postnatal day 1 (PN1) pups. This permitted to characterize the temporal pattern of expression of the main genes participating in the cellular transport, storage, and release of Zn during corticogenesis. It appears that cells of the immature cortex express a wide diversity of actors involved in Zn homeostasis with Zip7, SOD1, and metallothioneins being the most abundant transcripts throughout corticogenesis. The quantification of total Zn with XRF and ICP-AES reveals a reduction of Zn levels. Moreover, this is accompanied by a diminution of the size of the internal pools of mobilizable Zn. This study illustrates the tight temporal and spatial regulation of Zn homeostasis during cerebral brain development.