Clinical and primary cell evidence reveals complex CFTR function-phenotype relationships.

Area of Science:

• Biochemistry
• Genetics
• Medical Science

Background:

• The relationship between CFTR function and clinical phenotype is not fully understood, with prior studies showing mixed results.
• Defining this relationship is crucial for interpreting CFTR functional data and predicting treatment benefits.

Purpose of the Study:

• To define the genotype-function-phenotype relationship in cystic fibrosis.
• To integrate data from the CFTR2 registry and human nasal epithelial (HNE) studies.

Main Methods:

• Linked clinical data from 84,418 individuals in CFTR2 with CFTR functional measures from 289 genotypes.
• Calculated total genotype function as average percent wild-type chloride conductance.
• Applied piecewise linear and logarithmic regressions to evaluate the function-phenotype relationship in CFTR2 and HNE cohorts.

Main Results:

• Simple linear regression obscured data heterogeneity.
• Piecewise linear regressions showed a logarithmic pattern, with slope magnitude attenuating as function increased.
• HNE data corroborated this pattern, indicating greatest phenotypic gains at lower CFTR function levels.

Conclusions:

• The CFTR function-phenotype relationship is proportional, not linear, with outcomes varying by baseline function.
• This framework precisely predicts clinical benefits from CFTR-directed therapies.
• It identifies meaningful thresholds for CFTR functional restoration.