Genetic analysis of urinary traits in Scottish and Croatian populations and a functional study of Arl15 in the kidneys
Item statusRestricted Access
Embargo end date31/07/2022
Joseph, Christina Babu
Magnesium is the second most abundant bivalent cation in the body and is essential for many cellular processes. Electrolyte imbalance, including changes in magnesium concentration and other clinically relevant electrolyte ratios in the body, can result in dizziness and arrhythmia. If left untreated, this can result in serious illness or even death. Renal magnesium handling plays an important role in maintaining magnesium homeostasis, however the exact biological mechanisms remain unclear. A recent genome-wide association study (GWAS) identified an association between the ratio of urinary magnesium concentration to creatinine and variants in the ARL15 gene on chromosome 5. I expanded these analyses by performing meta-analyses for 29 urinary traits in 11,617 individuals from Scottish and Croatian populations. This identified additional genes that may be involved in these traits and confirmed that ARL15 is associated with urinary magnesium (uMg) related traits. The SNP with the most significant P value associated with uMg in the meta-analyses, rs35931, lies within an EGR1 transcription factor binding site in an enhancer region of ARL15. Individuals homozygous for the non-reference allele of rs35931 had lower urinary magnesium levels compared to individuals with the homozygous reference allele. Since ARL15 encodes a GTP-binding protein that regulates the magnesium transporter channel TRPM6, and other proteins involved in magnesium homeostasis in physiologically relevant cell lines, the hypothesis was that genetic variation affects the expression of ARL15, which, in turn modulates magnesium transport by regulating magnesium transporters. Functional studies were performed in order to investigate this and to elucidate the role of ARL15 in magnesium homeostasis both in vitro and in vivo. This confirmed that Arl15 interacts with magnesium transporters within the distal convoluted tubule segment of the kidneys. In vitro knockout models of Arl15 established using CRISPR-Cas9 gene editing in a mouse distal convoluted tubule cell-line showed significantly impaired magnesium transport. Furthermore, homozygous deletion of Arl15 is lethal at the organismal level in the mouse, highlighting the crucial role of ARL15 in health and disease.