Early role for a Na,K-ATPase () in brain development.

Osmotic equilibrium and membrane potential in animal cells depend on concentration gradients of sodium (Na) and potassium (K) ions across the plasma membrane, a function catalyzed by the Na,K-ATPase α-subunit. Here, we describe variants encoding dysfunctional α3-subunits in children affected by polymicrogyria, a developmental malformation of the cerebral cortex characterized by abnormal folding and laminar organization. To gain cell-biological insights into the spatiotemporal dynamics of prenatal expression, we built an transcriptional atlas of fetal cortical development using mRNA in situ hybridization and transcriptomic profiling of ∼125,000 individual cells with single-cell RNA sequencing (Drop-seq) from 11 areas of the midgestational human neocortex. We found that fetal expression of is most abundant to a subset of excitatory neurons carrying transcriptional signatures of the developing subplate, yet also maintains expression in nonneuronal cell populations. Moving forward a year in human development, we profiled ∼52,000 nuclei from four areas of an infant neocortex and show that expression persists throughout early postnatal development, most predominantly in inhibitory neurons, including parvalbumin interneurons in the frontal cortex. Finally, we discovered the heteromeric Na,K-ATPase pump complex may form nonredundant cell-type-specific α-β isoform combinations, including α3-β1 in excitatory neurons and α3-β2 in inhibitory neurons. Together, the developmental malformation phenotype of affected individuals and single-cell expression patterns point to a key role for α3 in human cortex development, as well as a cell-type basis for pre- and postnatal -associated diseases.