Differential gene expression in renal cortex resulting from SPAK gene disruption. Mus musculus

Poorly defined adaptive processes maintain salt balance when the renal thiazide-sensitive sodium-chloride cotransporter is inhibited, limiting diuretic efficacy. Here, we identify underlying mechanisms in SPAK kinase null mice, which are unable to phospho-activate NCC. Global transcriptional profiling, combined with biochemical, cell biological and physiological phenotyping, identified the gene expression signature of the response, and revealed how it establishes a new adaptive physiology. Salt reabsorption pathways are created by the coordinate induction of a multi-gene transport system, involving solute carriers (Slc26a; Slc4a8; Slc4a9), carbonic anhydrase isoforms, and V-type H+-ATPase subunits in pendrin-positive intercalated cells (PP-IC), and ENaC subunits in principal cells. A distal nephron remodeling process and induction of Jagged 1-Notch signaling, which expands the cortical connecting tubule with principal cells and replaces acid-secreting α- intercalated cells with PP-IC, is partly responsible. Salt reabsorption is also activated by induction of an alpha-ketoglutarate (α-KG) paracrine signaling system. Coordinate regulation of a multigene α-KG synthesis and transport pathway cause α-KG to be secreted into the pro-urine as the α-KG activated GPCR (Oxgr1) increases on the PP-IC apical surface, allowing paracrine delivery of α-KG to stimulate salt transport. Identification of the integrated compensatory NaCl reabsorption mechanisms provides new insights into thiazide diuretic efficacy. Overall design: Gene transcrtipt isolated form the renal cortex of 4 SPAK KO and 4 litter-mate WT animals was compared to evaluate differential gene expression with the goal of identifing a nextwork of genes that function cooperatively compensatory to mitigate renal salt loss when the SPAK function is lost.