Naturally occurring UBIAD1 mutations differentially affect menaquinone biosynthesis and vitamin K-dependent...

Area of Science:

• Biochemistry
• Genetics
• Cell Biology

Background:

• UbiA prenyltransferase domain-containing protein-1 (UBIAD1) synthesizes menaquinone-4 (MK-4), essential for vitamin K-dependent (VKD) protein carboxylation.
• Genetic UBIAD1 variations are linked to Schnyder corneal dystrophy (SCD), characterized by corneal cholesterol accumulation.
• SCD patient phenotypes don't fully align with observed MK-4 or VKD carboxylation defects.

Purpose of the Study:

• To investigate the functional impact of UBIAD1 mutations on MK-4 biosynthesis and VKD carboxylation in a cellular model.
• To establish a cell-based assay for evaluating UBIAD1 function and its relation to SCD.

Main Methods:

• CRISPR-Cas9 was used to create Ubiad1-deficient HEK293 cells expressing a VKD reporter.
• MK-4 production and reporter protein carboxylation efficiency were measured to assess UBIAD1 mutation effects.

Main Results:

• The N102S mutation moderately affected MK-4 synthesis but not VKD carboxylation.
• The G186R mutation significantly impaired both MK-4 biosynthesis and VKD carboxylation.
• Other UBIAD1 mutations showed varied impacts on MK-4 production and VKD carboxylation.

Conclusions:

• UBIAD1's MK-4 biosynthetic activity does not directly correlate with SCD patient phenotypes.
• The developed cell-based assays are valuable tools for studying UBIAD1 function in a cellular context.