The gene is NAMPT (Nicotinamide phosphoribosyltransferase), which:
"Catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, an intermediate in the biosynthesis of NAD. It is the rate limiting component in the mammalian NAD biosynthesis pathway."[1]
"Catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, an intermediate in the biosynthesis of NAD. It is the rate limiting component in the mammalian NAD biosynthesis pathway."[1]
[1] https://www.uniprot.org/uniprotkb/P43490/entry
Full paper:
https://www.science.org/doi/10.1126/sciadv.adx2407