# TRPM6 in murine kidneys—of targets and antibodies

## TL;DR

This study investigates the expression and localization of TRPM6 in mouse kidneys, highlighting challenges in antibody specificity and the need for better validation methods.

## Contribution

The paper emphasizes the limitations of current TRPM6 antibodies and proposes the use of conditional knockouts for more accurate analysis.

## Key findings

- TRPM6 immunostaining was observed in both proximal and distal tubules of murine kidneys.
- Conditional trpm6 knockout mice showed similar antibody signals as wildtype, suggesting potential epitope overlap.
- Commercial TRPM6 antibodies lack sufficient validation, complicating interpretation of immunohistochemistry results.

## Abstract

Magnesium is the fourth most abundant cation in the human organism. As a key-player in many enzymatic reactions, magnesium homeostasis disbalance can cause severe disorders. In the early 2000s, the transient receptor potential melastatin channel 6 (TRPM6) was identified as a critical protein in renal Mg2+-reabsorption in the distal convoluted tubule (DCT). As the key-interface responsible for salt/water adaptation to environmental changes, the kidney is a highly dynamic system. Therefore, renal TRPM6 expression and Mg2+-reabsorption might not be restricted to the DCT, as previously indicated. To address this, protein targeting is mandatory since genomic detection is insufficient to conclude on functional expression. For this purpose, we used a polyclonal TRPM6 antibody from an established manufacturer and detected immunostaining in murine proximal and distal tubules. As a matter of fact, the specificity of most commercially available TRPM6 antibodies is insufficiently validated which relies on the lack of constitutive trpm6 knockouts. Therefore, conditional trpm6 knockout mice were used for control experiments. Similar signals were observed in the knockout tissue when compared to wildtype using the TRPM6 antibody. Overlaps with TRPM7 epitopes or other peptides are conceivable. Thus, TRPM6 immunohistochemistry and immunofluorescence results are difficult to interpret, and the spectrum of renal TRPM6 expression is not yet elucidated.