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Role of Alström syndrome 1 in the regulation of blood pressure and renal function
Ankita Bachhawat Jaykumar, Paulo S. Caceres, Keyona N. King-Medina, Tang-Dong Liao, Indrani Datta, Dipak Maskey, Jürgen K. Naggert, Mariela Mendez, William H. Beierwaltes, Pablo A. Ortiz
Ankita Bachhawat Jaykumar, Paulo S. Caceres, Keyona N. King-Medina, Tang-Dong Liao, Indrani Datta, Dipak Maskey, Jürgen K. Naggert, Mariela Mendez, William H. Beierwaltes, Pablo A. Ortiz
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Research Article Cell biology

Role of Alström syndrome 1 in the regulation of blood pressure and renal function

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Abstract

Elevated blood pressure (BP) and renal dysfunction are complex traits representing major global health problems. Single nucleotide polymorphisms identified by genome-wide association studies have identified the Alström syndrome 1 (ALMS1) gene locus to render susceptibility for renal dysfunction, hypertension, and chronic kidney disease (CKD). Mutations in the ALMS1 gene in humans causes Alström syndrome, characterized by progressive metabolic alterations including hypertension and CKD. Despite compelling genetic evidence, the underlying biological mechanism by which mutations in the ALMS1 gene lead to the above-mentioned pathophysiology is not understood. We modeled this effect in a KO rat model and showed that ALMS1 genetic deletion leads to hypertension. We demonstrate that the link between ALMS1 and hypertension involves the activation of the renal Na+/K+/2Cl– cotransporter NKCC2, mediated by regulation of its endocytosis. Our findings establish a link between the genetic susceptibility to hypertension, CKD, and the expression of ALMS1 through its role in a salt-reabsorbing tubular segment of the kidney. These data point to ALMS1 as a potentially novel gene involved in BP and renal function regulation.

Authors

Ankita Bachhawat Jaykumar, Paulo S. Caceres, Keyona N. King-Medina, Tang-Dong Liao, Indrani Datta, Dipak Maskey, Jürgen K. Naggert, Mariela Mendez, William H. Beierwaltes, Pablo A. Ortiz

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Figure 7

Surface NKCC2 expression is higher in TALs from ALMS1-deleted rats.

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Surface NKCC2 expression is higher in TALs from ALMS1-deleted rats.
(A) ...
(A) NKCC2 surface fraction in thick ascending limbs (TALs) from ALMS1-KO rats was higher (ALMS1-KO, 13.8% ± 1.2%, vs. WT, 8.1% ± 1.1%, n = 6;*P < 0.05). The lanes were run on the same gel but were noncontiguous. (B) Total NKCC2 expression normalized by the housekeeping control protein GAPDH in TALs from WT and ALMS1-KO rats was similar (normalized value ALMS1-KO, 0.88 ± 0.07, vs. WT, 1, n = 5). (C) ALMS1 mRNA expression in TALs from normal Sprague Dawley rats measured 7 days after in vivo transduction of ALMS1 shRNA in rat outer medulla was decreased compared with control (normalized value ALMS1 shRNA, 0.19 ± 0.04, vs. control, 1, n = 3; *P < 0.01). (D) ALMS1 protein expression normalized to GAPDH (different exposure) in TALs from normal Sprague Dawley rats measured 7 days after in vivo transduction of ALMS1 shRNA was decreased, indicating effective knock down of ALMS1 in rat outer medulla (normalized value ALMS1 shRNA, 0.39 ± 0.2, vs. control, 1, n = 4; *P < 0.05). (E) Surface NKCC2 expression measured by surface biotinylation in TALs from normal Sprague Dawley rat kidney transduced with ALMS1 shRNA was enhanced compared with kidney injected with control (ALMS1 shRNA, 11.1% ± 1.6%, vs. control, 6.6% ± 0.8%, n = 5; *P < 0.05). (F) Total NKCC2 expression normalized to GAPDH in TALs from normal Sprague-Dawley rat kidney transduced with ALMS1 shRNA was similar to control injected kidney (normalized value ALMS1 shRNA, 0.93 ± 0.07, vs. control, 1; n = 5). Values represent mean ± SEM, and statistical analysis was performed with 2-tailed Student’s t test.

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