2-210595535-G-C

Position:

• chr2-210595535-G-C

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_001875.5(CPS1):​c.1312G>C​(p.Ala438Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000548 in 1,459,714 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A438T) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000055 (0 hom.)
• Consequence: CPS1 NM_001875.5 missense
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 9.60

Genes affected

CPS1 (HGNC:2323): (carbamoyl-phosphate synthase 1) The mitochondrial enzyme encoded by this gene catalyzes synthesis of carbamoyl phosphate from ammonia and bicarbonate. This reaction is the first committed step of the urea cycle, which is important in the removal of excess urea from cells. The encoded protein may also represent a core mitochondrial nucleoid protein. Three transcript variants encoding different isoforms have been found for this gene. The shortest isoform may not be localized to the mitochondrion. Mutations in this gene have been associated with carbamoyl phosphate synthetase deficiency, susceptibility to persistent pulmonary hypertension, and susceptibility to venoocclusive disease after bone marrow transplantation.[provided by RefSeq, May 2010]

CPS1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 16 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr2-210595535-G-A is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.987
• PP5: Variant 2-210595535-G-C is Pathogenic according to our data. Variant chr2-210595535-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 449391.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-210595535-G-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CPS1	NM_001875.5	c.1312G>C	p.Ala438Pro	missense_variant	13/38	ENST00000233072.10	NP_001866.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CPS1	ENST00000233072.10	c.1312G>C	p.Ala438Pro	missense_variant	13/38	1	NM_001875.5	ENSP00000233072.5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000548 AC: 8 AN: 1459714 Hom.: 0 Cov.: 30 AF XY: 0.00000413 AC XY: 3 AN XY: 726240

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000253

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000540

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Congenital hyperammonemia, type I Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	May 05, 2023	In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. Experimental studies have shown that this missense change affects CPS1 function (PMID: 23649895). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on CPS1 protein function. ClinVar contains an entry for this variant (Variation ID: 449391). This missense change has been observed in individuals with carbamoyl phosphate synthetase deficiency (PMID: 17310273, 23649895; Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with proline, which is neutral and non-polar, at codon 438 of the CPS1 protein (p.Ala438Pro). -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Feb 17, 2023	Variant summary: CPS1 c.1312G>C (p.Ala438Pro) results in a non-conservative amino acid change located in the Carbamoyl-phosphate synthase large subunit, CPSase domain (IPR005483) of the encoded protein sequence. Four of four in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 250618 control chromosomes (gnomAD). c.1312G>C has been reported in the literature in one individual affected with Carbamoylphosphate Synthetase I Deficiency (Kurokawa_2007). At least one publication reports experimental evidence evaluating an impact on protein function showing an almost undetectable level of enzyme activity and decreased thermostability (Diez-Fernandez_2013). Three clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Aug 29, 2017

The A438P variant in the CPS1 gene has previously been reported in association with CPS1 deficiency in an individual who was also heterozygous for a second variant in CPS1, although the phase of these variants was not reported (Kurokawa et al., 2007). Functional analysis of A438P found that it is associated with significantly reduced enzyme activity (Diez-Fernandez et al., 2013). The A438P variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The A438P variant is a semi-conservative amino acid substitution, which may impact secondary protein structure as these residues differ in some properties. This substitution occurs at a position that is conserved across species. In silico analysis predicts this variant is probably damaging to the protein structure/function. In summary, we interpret A438P to be a likely pathogenic variant. -

Pulmonary hypertension, neonatal, susceptibility to;C4082171:Congenital hyperammonemia, type I Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Nov 19, 2021

- -

Pulmonary hypertension, neonatal, susceptibility to Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

May 30, 2023

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.92	.;D;T
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D;D
M_CAP	Pathogenic	0.40	D
MetaRNN	Pathogenic	0.99	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.8	.;H;.
PrimateAI	Pathogenic	0.86	D
PROVEAN	Pathogenic	-4.7	D;D;.
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0010	D;D;.
Sift4G	Pathogenic	0.0010	D;D;D
Polyphen		1.0	.;D;.
Vest4		0.89
MutPred		0.96		.;Loss of catalytic residue at A438 (P = 0.0076);Loss of catalytic residue at A438 (P = 0.0076);
MVP		0.98
MPC		0.97
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.93
gMVP		0.96

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs772497399; hg19: chr2-211460259; COSMIC: COSV51804767;