Uridine 5'-monophosphate synthase (UMPS) is an enzyme involved in de novo pyrimidine biosynthesis. This pathway also involves cytosolic carbamoyl-phosphate synthetase II, aspartate transcarbamylase, dihydroorotase (CAD), and mitochondrial dihydroorotate dehydrogenase (DHODH). UMPS is crucial for generating uridine monophosphate, which is essential for DNA and RNA synthesis, thus playing a fundamental role in cell proliferation and various biological processes [1].

Mutations in the UMPS gene can lead to hereditary orotic aciduria (HOA), a rare inborn error of pyrimidine metabolism. In a reported case, a 17-year-old Emirati girl with a novel homozygous variant in the UMPS gene presented with recurrent infections, pancytopenia, failure to thrive, developmental delay, and epilepsy. Treatment with uridine triacetate led to clinical, hematologic, and biochemical improvement [2]. Another study identified a novel missense mutation c.517G>C in the UMPS gene associated with mild orotic aciduria in a Chinese-origin pedigree. The proband had epilepsy and intellectual disability, while other mutation carriers had mild orotic aciduria without relevant medical complaints [3]. Heterozygous UMPS mutations can also lead to mild and isolated orotic aciduria without clinical consequence, as seen in 11 unrelated individuals and 19 clinically asymptomatic family members [4].

In conclusion, UMPS is essential for de novo pyrimidine biosynthesis, which is vital for DNA and RNA synthesis and cell proliferation. Research on UMPS-related mutations in models, though not directly from KO/CKO mouse models in the provided references, has revealed its role in rare genetic disorders like hereditary orotic aciduria. Understanding UMPS function and its associated mutations can potentially contribute to better diagnosis and treatment of such diseases.