RFT1 deficiency in three novel CDG patients

Area of Science:

• Biochemistry
• Genetics
• Molecular Biology

Background:

• N-glycosylation is crucial for protein function, and defects lead to Congenital Disorders of Glycosylation (CDG).
• The RFT1 protein facilitates the translocation of a key N-glycosylation precursor across the endoplasmic reticulum membrane.
• Previous identification of an RFT1-deficient CDG patient highlighted the protein's importance.

Purpose of the Study:

• To identify and characterize novel patients with RFT1 deficiency, a cause of CDG.
• To delineate the clinical phenotype and molecular basis of RFT1-CDG.
• To confirm the role of RFT1 in Man(5)GlcNAc(2)-PP-dolichol translocation.

Main Methods:

• Genetic analysis to identify mutations in the RFT1 gene.
• Biochemical assays to measure Man(5)GlcNAc(2)-PP-dolichol accumulation and recombinant DNase 1 secretion.
• Complementation studies using patient fibroblasts expressing normal RFT1 cDNA.

Main Results:

• Three novel CDG patients with RFT1 deficiency were identified, presenting with homozygous missense mutations (p.R67C, p.K152E, p.E298K).
• Patients exhibited accumulation of Man(5)GlcNAc(2)-PP-dolichol and reduced recombinant DNase 1 secretion.
• Expression of normal RFT1 cDNA corrected glycosylation patterns and DNase 1 secretion in patient fibroblasts.
• Clinical phenotypes included typical CDG symptoms and sensorineural deafness.

Conclusions:

• RFT1 deficiency is a significant cause of CDG, characterized by impaired N-glycosylation precursor translocation.
• Novel mutations in RFT1 further expand the genetic spectrum of RFT1-CDG.
• Sensorineural deafness is a notable clinical feature in RFT1-CDG patients.
• These findings underscore the critical role of RFT1 in cellular glycosylation processes.