Establishment of an in vivo model for KCNJ5 dependent hyperaldosteronism

U Lichtenauer; PL Schmid; A Oßwald; I Renner-Müller; M Reincke; R Warth; E Wolf; F Beuschlein

doi:10.1055/s-0035-1547718

Experimental and Clinical Endocrinology & Diabetes, Table of Contents

Establishment of an in vivo model for KCNJ5 dependent hyperaldosteronism

U Lichtenauer ¹, PL Schmid ¹, A Oßwald ², I Renner-Müller ³, M Reincke ⁴, R Warth ⁵, E Wolf ³, F Beuschlein ¹

¹Medizinische Klinik und Poliklinik IV, Klinikum der Universität München
²Medizinische Klinik und Poliklinik IV; Klinikum der Universität München
³Lehrstuhl für Molekulare Tierzucht und Biotechnologie, Genzentrum der Lmu München
⁴Universität München; Medizinische Klinik und Poliklinik IV; Med. Klinik und Poliklinik IV
⁵Universität Regensburg; Institut für Physiologie/Nephrologie; Klinik für Innere Medizin II

Abstract

Next generation sequencing allowed the detection of genetic alterations in the KCNJ5 gene in 30% of cases of primary hyperaldosteronism, resulting in a calcium influx, higher aldosterone synthase activity, and a more severe clinical phenotype. A suitable in vivo model to date is lacking.

Applying pronuclear DNA injection, C57BL/6 mice were obtained expressing either a full length human KCNJ5 wild type gene, or the mutant genes KCNJ5 ^G451A or KCNJ5 ^T503G under the control of a promotor fragment of the Akr1b7 gene for adrenocortical specific expression. The initial characterization of 8 eight week old animals of each sex and genotype (n = 49 females and n = 41 males) revealed no obvious morphological differences. Accordingly, significant differences in body and kidney weight between genotype and gender could not be found. However, adrenal weight in female animals was significantly lower in KCNJ5 ^G451A (4.59 ± 0.18 mg) compared to KCNJ5 ^wt (5.27 ± 0.22 mg, p = 0.03) animals, while adrenal weight tended to be higher (4.37 ± 0.19 vs. 3.72, p = 0.05) in male animals. In KCNJ5 ^T503G mice, the adrenal weight was similar within female and male animal groups compared KCNJ5 ^wt mice.

On the functional level, aldosterone synthase (Cyp11b2) levels tended to be higher expressed in female KCNJ5 ^G451A animals (154 ± 20%, p = 0.057), while Hsd3b1 (161 ± 14%, p = 0.001), Cyp11b1 (185 ± 16%, p < 0.001), Cyp11a1 (168 ± 16%, p = 0.003), and Star (159 ± 9%, p = 0.001) were relevantly upregulated compared to KCNJ5 ^wt mice (100 ± 15%, 100.0 ± 2%, 100 ± 5%, 100 ± 7%, 100 ± 11% respectively). Female KCNJ5 ^T503G mice revealed significantly higher expression levels for Cyp11b2 (152 ± 15%, p = 0.028), Hsd3b1 (124 ± 10%, p = 0.031), and Cyp11b1 (134 ± 9%, p = 0.007) compared to KCNJ5 ^wt mice. No significant differences in the expression levels of these genes were found in all male animals, except for Cyp11a1 downregulation (KCNJ5 ^G451A: 42 ± 1%, p < 0.001 and KCNJ5 ^T503G: 72 ± 2%, p = 0.004, vs. 100%± 3.2% in KCNJ5 ^wt mice).

Following initial phenotyping, this model should allow the exploration of KCNJ5 mediated aldosterone excess and might be suited as a humanized model for future targeted therapies.