R560S: A class II CFTR mutation that is not rescued by current modulators

Area of Science:

• Molecular Biology
• Genetics
• Medical Research

Background:

• Over 2000 cystic fibrosis transmembrane conductance regulator (CFTR) mutations exist, complicating drug development.
• The functional impact and modulator responsiveness of rare CFTR mutations remain largely unknown.

Purpose of the Study:

• To characterize the rare R560S CFTR mutation using patient-derived tissues and cellular models.
• To assess the functional and biochemical response of R560S-CFTR to available CFTR modulators.

Main Methods:

• Utilized patient rectal biopsies and derived intestinal organoids.
• Generated a novel cell line expressing R560S-CFTR.
• Assessed CFTR mRNA, protein processing, and channel function via RT-PCR, Western blot, and forskolin-induced swelling assays.

Main Results:

• R560S mutation does not affect CFTR mRNA splicing.
• R560S significantly impairs CFTR protein processing, preventing mature form production.
• R560S-CFTR exhibits no chloride channel function.
• Tested CFTR modulators failed to rescue R560S-CFTR processing or function.

Conclusions:

• R560S is classified as a Class II CFTR mutation.
• Unlike F508del, the R560S mutation is not responsive to current CFTR modulator therapies.