Abstract: SA-PO850
Functional Characterization of A1CF, a Novel eGFR Locus
Session Information
- Molecular Mechanisms of CKD - III
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 1903 CKD (Non-Dialysis): Mechanisms
Authors
- Lin, Jennie, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
- Tauber, Philipp, The Jackson Laboratory, Bar Harbor, Maine, United States
- Takemon, Yuka, The Jackson Laboratory, Bar Harbor, Maine, United States
- Park, Jihwan, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Gewin, Leslie S., Vanderbilt University, Nashville, Tennessee, United States
- Susztak, Katalin, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Korstanje, Ron, The Jackson Laboratory , Bar Harbor, Maine, United States
Background
A recent human genome-wide association study identified a common 5' UTR variant at the A1CF locus associated with eGFR. A1CF encodes an RNA binding protein (RBP) previously known to facilitate APOBEC1’s editing of APOB mRNA in non-renal tissues to produce a shorter isoform. However, A1CF's role in modulating renal function remains unclear.
Methods
Leveraging human and rodent systems, we studied A1CF in a renal context with an integrated approach. We localized A1CF expression in human kidney organoids and mouse kidneys and assessed expression in human nephrectomy tissue and mouse models of renal fibrosis. Next we used RIP-seq to identify A1CF's RNA binding targets and their enriched pathways. To determine A1CF's renal effects in vivo, we measured markers of renal function and injury at baseline and after induction of stress conditions in A1cf knockout mice.
Results
Immunostaining of human kidney organoids and fluorescent RNA labeling of mouse kidneys demonstrate that A1CF expression is specific to the proximal tubule. Profiling of human nephrectomy tissue revealed that A1CF mRNA expression is decreased in CKD samples compared to healthy control (N=58, P=7.4 x 10-4), correlates positively with eGFR (P= 9.5 x 10-5), and correlates negatively with percent interstitial fibrosis (P=2.0 x 10-6). This decreased expression was recapitulated in mice with folic acid (FA) nephropathy and unilateral ureteral obstruction (UUO) on the mRNA (P=2.7 x 10-7; P=3.4 x 10-13) and protein levels (P=6.4x10-4; P=1.9x10-7). To investigate how A1CF as an RBP might interact with injury pathways, we performed RIP-seq and identified 276 binding targets which were enriched in pathways for endoplasmic reticulum protein trafficking (P=6.6 x 10-5) and peroxisomal function (P=3.6 x 10-4), relevant to intracellular stress when perturbed. Although no baseline abnormalities were detected in A1cf ko mice, when subjected to stress of water deprivation or FA treatment we observed an increase in urinary albumin to creatinine ratio (N=16, P=0.03; N=16, P=8.0 x 10-3). Furthermore, after FA treatment, A1cf ko mice exhibited higher Bax/Bcl-2 ratios and higher Acta2 expression in the kidney (N=7, P=0.01, P=4x10-3).
Conclusion
Taken together, these findings suggest that A1CF plays a previously undiscovered role in modulating the intracellular stress response relevant to CKD.
Funding
- Other NIH Support