Background: The variability in response to CFTR modulatory drugs in cystic fibrosis (CF) has recently been associated with modifier genes - namely alternative chloride channels - in individuals with the same CFTR genotype. Objective: To analyze CFTR response to VX-809/VX-770 drugs in conditionally reprogrammed cells (CRC) of human nasal epithelium (HNE) from F508del/F508del patients with different allelic variants at the SNP rs7512462 in the Solute Carrier Family 26, Member 9 (SLC26A9; MIM: 608481) gene. Method: Measurements of equivalent open short-circuit currents (Isc-eq) of primary nasal epithelial cells from F508del/F508del patients (n=12) for CFTR function were performed in micro Ussing chambers and compared with non-CF controls (n=2). Data were analyzed according to the rs7512462 genotypes in the SLC26A9 gene which were determined by real-time PCR. Results: The CRC-HNE cells from F508del/F508del patients evidenced high variability in the basal levels of CFTR function and in their responses to CFTR modulator drugs (VX-809/VX-770). However, we found a correlation with the SLC26A9 rs7512462 variant: in the presence of the C allele, increased basal CFTR function was observed as well as higher responses to VX-809 VX-770. The genotypes CC CT together evidenced CFTR function levels of 14.89% relatively to wt/wt (CT alone -15.29%) i.e., almost double of TT genotype (7.13%). Furthermore, sweat [Cl-] and body mass index (BMI) of CF patients also evidenced a correlation with the rs7512462 genotype (TT, CT and CC CT), which however, was not observed for lung function (FEV1, FVC, FEV1/FVC or FEF25-75%). Conclusion: This study demonstrates that CFTR function can be performed in patient-derived CRC-HNEs. Moreover, we demonstrate here that CFTR function in CRC-HNEs from F508del/F508del patients and responses to the VX-809 VX-770 combination as well as clinical data, all correlate with the SLC26A9 rs7512462 variant. This variant thus partially sheds light on the generally observed inter-individual phenotypic variability and in personalized responses to CFTR modulator drugs. Funding Statement: Work supported by research grants #2015/14666-3 – FAPESP; FALM – FAPESP and fellowship #2015/12858-5; the Fund for the Support to Education, Research, and Extension of the University of Campinas, for fellowship #0648/2015; and JDR: FAPESP, for fellowship #2015/12183-8. AK was also supported by CAPES fellowship – 01P3368/2015 – 2017 and ‘Ciencias Sem Fronteiras’ CAPES – 053/2012 (to MDA) and work in MDA lab is supported by UID/MULTI/04046/2013 center grant from FCT, Portugal (to BioISI). Declaration of Interests: The authors declare no competing financial interests. Ethics Approval Statement: The participants of this study signed the Informed Consent Form under approval of the Ethics Committee from the University of Campinas (#91.041.317). The procedures performed are in accordance with the Helsinki Declaration.
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