Increased expression of anion transporter SLC26A9 delays diabetes onset in cystic fibrosis
Anh-Thu N. Lam, … , Scott M. Blackman, Garry R. Cutting
Anh-Thu N. Lam, … , Scott M. Blackman, Garry R. Cutting
Published October 3, 2019
Citation Information: J Clin Invest. 2020;130(1):272-286. https://doi.org/10.1172/JCI129833.
View: Text | PDF
Research Article Endocrinology Genetics

Increased expression of anion transporter SLC26A9 delays diabetes onset in cystic fibrosis

Abstract

Diabetes is a common complication of cystic fibrosis (CF) that affects approximately 20% of adolescents and 40%–50% of adults with CF. The age at onset of CF-related diabetes (CFRD) (marked by clinical diagnosis and treatment initiation) is an important measure of the disease process. DNA variants associated with age at onset of CFRD reside in and near SLC26A9. Deep sequencing of the SLC26A9 gene in 762 individuals with CF revealed that 2 common DNA haplotypes formed by the risk variants account for the association with diabetes. Single-cell RNA sequencing (scRNA-Seq) indicated that SLC26A9 is predominantly expressed in pancreatic ductal cells and frequently coexpressed with CF transmembrane conductance regulator (CFTR) along with transcription factors that have binding sites 5′ of SLC26A9. These findings were replicated upon reanalysis of scRNA-Seq data from 4 independent studies. DNA fragments derived from the 5′ region of SLC26A9-bearing variants from the low-risk haplotype generated 12%–20% higher levels of expression in PANC-1 and CFPAC-1 cells compared with the high- risk haplotype. Taken together, our findings indicate that an increase in SLC26A9 expression in ductal cells of the pancreas delays the age at onset of diabetes, suggesting a CFTR-agnostic treatment for a major complication of CF.

Authors

Anh-Thu N. Lam, Melis A. Aksit, Briana Vecchio-Pagan, Celeste A. Shelton, Derek L. Osorio, Arianna F. Anzmann, Loyal A. Goff, David C. Whitcomb, Scott M. Blackman, Garry R. Cutting

×

Figure 3

TSS of SLC26A9 in pancreas.

Options: View larger image (or click on image) Download as PowerPoint
TSS of SLC26A9 in pancreas. (A) Schematic in native orientation showing ...
(A) Schematic in native orientation showing the first 5 exons of the SLC26A9 gene. Note: SLC26A9 is transcribed from the minus strand. The size of exon and intron regions are labeled (nt). Hatch marks denote where the figure is not drawn to scale. (B) Summary of sequence of 5′ RACE obtained from 1 primary human pancreas RNA. 5′ RACE was performed using a gene-specific primer (GSP) in exon 5 of SLC26A9. The portion of the GSP in red is the overhang necessary for infusion PCR. TSS marks the beginning of exon 1. The translational start site with the Kozak consensus sequence occurs in exon 2. (C) Sanger sequencing trace of the 5′ RACE product from the SLC26A9 mRNA transcripts in human pancreas. Upstream of the TSS is the RACE adapter sequence confirming the 5′ most extent of the RACE product. The sequencing trace crosses exon/exon junctions (shown here between exon 1 and 2 by the vertical black line) confirming that RACE used mRNA as the template. Sanger sequencing of 5′ RACE products obtained from primary human lung (n = 3) and stomach (n = 1) samples identified the same TSS (not shown).