Sheep erythrocyte potassium locus highlights MYADM family regulation of electroneutral potassium chloride cotransporters (KCC)

Abstract Some domestic sheep have distinct low (LK) or high intracellular potassium (HK) erythrocytes with demonstrated differences in potassium chloride co-transport. Erythrocyte potassium concentration is inherited as a single locus trait, although responsible genetic variant(s) have not been identified. Herein, genome-wide association identified a large, artiodactyl-specific tandem duplication of the MYADM gene family locus as highly associated ( P = 1.1 × 10 − 63 ) with erythrocyte intracellular potassium concentration. The full tandemly expanded MYADMF locus included 37 genes in sheep, 33 genes in goats, 52 genes in cattle, and 15 genes in domestic swine, but no comparable tandemly expanded locus in horses. Fine mapping in an expanded sheep population showed maximal association with erythrocyte potassium ( P < 10 − 99 ) for MYADMF15A1 , MYADMF1G1 , MYADMF1H1 , MYADMF3A1 , MYADMF1B3 , and MYADMF13C1 . Prior data showed higher potassium chloride co-transport in sheep LK than HK erythrocytes, and the present data, for the first time, implicate one or more MYADMF genes in the regulation of potassium chloride co-transport. Since there are many fewer MYADM genes in humans, we hypothesized that a simpler interaction might exist with the gene family namesake MYADM , which has been linked to human hypertension in multiple studies. Alphafold3 protein models suggest MYADM interacts directly with KCC3 to stabilize its N-terminal regulatory peptide in the inhibitory position. While the complexity of the MYADMF expanded repeat locus makes it more difficult to draw conclusions about causation, it is possible that divergent alleles such as MYADMF1G1 and MYADMF1B3 , or possibly MYADMF15A1 , cause the low potassium phenotype through interaction with KCC3 and effects on the N-terminal regulatory peptide. Cumulatively, these data identify an expanded MYADMF locus as the major controller of sheep erythrocyte potassium concentration and suggest direct interaction of MYADM proteins with KCC transporters may regulate their function in diverse contexts. Additional work is needed to confirm structural predictions and explore functional implications.