Identification of novel variants in carbamoyl phosphate synthetase 1 gene and comparative pathogenicity assessments of CPS1 missense variants following ACMG/AMP-ClinGen recommendation for computational tools

Carbamoyl phosphate synthetase I (CPS1) deficiency is a rare autosomal recessive metabolic abnormality cause by dysfunctionality of CPS1 and often result in unfavorable outcome. In this study, we presented the detailed laboratory features and genetic analysis of two patients with heterozygous variants of CPS1, c.1927 A > G (p.Asn643Asp), c.2375 T > G (p.Met792Arg), c.3443 T > A (p.Met1148Lys) in patient 1; c.3784C > T (p.Arg1262Ter), c.3734 T > A (p.Leu1245His) in patient 2, respectively. c.1927 A > G (p.Asn643Asp) and c.2375 T > G (p.Met792Arg) are novel out of 5 variants and classified as variants of uncertain significance (VUS) under the guidelines of ACMG/AMP-ClinGen. Structure-based analysis of 4 missense variants indicates deleterious alterations to the protein. Since the employment of genetic testing as a clinical diagnostic tool, distinguishing pathogenic from polymorphic changes poses significant problems for geneticists. As recommendation for PP3/BP4, the computational tools for missense variant have been published, we performed a comparative evaluation for pathogenicity interpretation in our patients and in ClinVar database regarding CPS1 missense variants under the updated guidelines of ACMG/AMP-ClinGen. The application of computational tools under the ACMG/AMP-ClinGen criteria revealed an increased sensitivity for pathogenicity evaluation, from variants of uncertain significance (VUS) to likely pathogenic (LP) in previously reported cases; while for variants without clinic information in the ClinVar database, the pathogenicity assessment of VUS remained, and shows a more optimistic and reliable clinical application in molecular diagnosis.