# Human-specific Abnormal Alternative Splicing of the Wild-type PKD1 Gene Induces Premature Termination of Polycystin-1

> **NIH NIH R01** · UNIVERSITY OF KANSAS MEDICAL CENTER · 2020 · $336,600

## Abstract

Project Summary
There are two major theories concerning the pathogenesis of ADPKD; the first and most accepted is that an
individual is born with a defective allele and then the normal WT allele undergoes a somatic mutation that gives
rise first to a tubular dilation and then a cyst, the `two hit' hypothesis. The second idea is that gene dosage is
enough to cause disease, the level of the protein product of the PKD1 gene, polycystin-1 (PC1) decreases below
a threshold and cysts appear in a stochastic manner. We wish to investigate these two ideas in a novel manner
using the fact that PC1, PC2 and fibrocystin are all present on an exosome we term the exosome-like vesicle
(ELV). We know that the level of PC1 is decreased in individuals with PKD1 mutations and that the amount of
PC1 per ELV is inversely proportional to height adjust total kidney volume (HtTKV). Observing the total amount
of PC1 in pooled exosomes tells us little about the pathogenesis of the disease. However, a new technology has
become available which allows an investigator to determine the amount of PC1 on individual ELVs, NanoView.
We know that ELVs contain CD133 (prominin) which colocalizes on exosomes with PC1. We predict that if the
`two hit' hypothesis is true, then clones of PKD1 null cells in the kidney will produce ELVs that are CD133+ and
PC1- and that the NanoView will see a bimodal distribution of PC1+ ELVs in ADPKD but not in normal urine.
The ratio of CD133+/PC- to CD133+/PC1+ ELVs will correlate with HtTKV. If haploinsufficiency is the
mechanism, then the mean intensity of PC1 per ELV will be inversely proportional to HtTKV. Thus, NanoView
technology can distinguish between the `two hit' and haploinsufficiency models.
To further dissect the mechanism of haploinsufficiency we will investigate two major ideas. The first is that the
human PKD1 gene is unusual in that it has two long CT rich tracts in introns 21 and 22 which interfere with
splicing and generate a smaller form of PC1, we term Trunc_PC1. We will investigate the possibility that splicing
efficiency correlates inversely with HtTKV. The second idea is that there is person to person variation in PKD1
promoter strength and that the promoter attenuates with age. We will investigate this possibility using real time
RT-PCR. We think that the different mechanisms have a profound effect on the way the disease may be treated.
If haploinsufficiency is correct, then strategies designed to increase the amount of endogenous PKD1 mRNA
and PC1 protein will be appropriate whereas in the `two hit' scenario these strategies will not work and may be
deleterious as both alleles are defective.

## Key facts

- **NIH application ID:** 10122431
- **Project number:** 1R01DK122205-01A1
- **Recipient organization:** UNIVERSITY OF KANSAS MEDICAL CENTER
- **Principal Investigator:** CHRISTOPHER J WARD
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $336,600
- **Award type:** 1
- **Project period:** 2020-09-15 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10122431

## Citation

> US National Institutes of Health, RePORTER application 10122431, Human-specific Abnormal Alternative Splicing of the Wild-type PKD1 Gene Induces Premature Termination of Polycystin-1 (1R01DK122205-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10122431. Licensed CC0.

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