rs1554725034

Positions:

• chr9-130494867-G-T

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PM2 PM5 PP3 PP5_Very_Strong

The NM_054012.4(ASS1):​c.971G>T​(p.Gly324Val) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000411 in 1,461,094 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 14/23 in silico tools predict a damaging outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. 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. G324S) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000041 (0 hom.)
• Consequence: ASS1 NM_054012.4 missense, splice_region
• Scores: Splicing: ADA: 0.9972
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 9.29

Genes affected

ASS1 (HGNC:758): (argininosuccinate synthase 1) The protein encoded by this gene catalyzes the penultimate step of the arginine biosynthetic pathway. There are approximately 10 to 14 copies of this gene including the pseudogenes scattered across the human genome, among which the one located on chromosome 9 appears to be the only functional gene for argininosuccinate synthetase. Mutations in the chromosome 9 copy of this gene cause citrullinemia. Two transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Aug 2012]

ACMG classification

Verdict is Pathogenic. Variant got 13 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr9-130489464-G-A is described in Lovd as [Pathogenic].
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.
• PP5: Variant 9-130494867-G-T is Pathogenic according to our data. Variant chr9-130494867-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 458676.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr9-130494867-G-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ASS1	NM_054012.4	c.971G>T	p.Gly324Val	missense_variant, splice_region_variant	13/15	ENST00000352480.10	NP_446464.1
ASS1	NM_000050.4	c.971G>T	p.Gly324Val	missense_variant, splice_region_variant	14/16		NP_000041.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ASS1	ENST00000352480.10	c.971G>T	p.Gly324Val	missense_variant, splice_region_variant	13/15	1	NM_054012.4	ENSP00000253004	P1
ASS1	ENST00000372393.7	c.971G>T	p.Gly324Val	missense_variant, splice_region_variant	14/16	5		ENSP00000361469	P1
ASS1	ENST00000372394.5	c.971G>T	p.Gly324Val	missense_variant, splice_region_variant	14/16	2		ENSP00000361471	P1
ASS1	ENST00000372386.6	n.242G>T		splice_region_variant, non_coding_transcript_exon_variant	4/6	3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000411 AC: 6 AN: 1461094 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 726866

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000450

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Citrullinemia Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jun 24, 2024	Variant summary: ASS1 c.971G>T (p.Gly324Val) results in a non-conservative amino acid change in the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. Several computational tools predict a significant impact on normal splicing: Two predict the variant weakens a 3' acceptor site. Two predict the variant strengthens a cryptic 3' acceptor site. However, these predictions have yet to be confirmed by functional studies. The variant was absent in 251114 control chromosomes (gnomAD). c.971G>T has been reported in the literature as a biallelic compound heterozygous genotype in individuals affected with Citrullinemia Type I (example: Martin-Hernandez_2014, Pangalos_2016, Diez-Fernandez_2017, Zielonka_2019). These data indicate that the variant is likely to be associated with disease. To our knowledge, no variant specific experimental evidence demonstrating an impact on protein function has been reported, although compound heterozygous genotypes with decreased ASS1 enzyme activity have been reported (example, Zielonka_2019). The following publications have been ascertained in the context of this evaluation (PMID: 25433810, 28111830, 31469252, 27168972). ClinVar contains an entry for this variant (Variation ID: 458676). Based on the evidence outlined above, the variant was classified as likely pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Sep 04, 2023	This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of citrullinemia (PMID: 25433810, 28111830, 31469252; Invitae). ClinVar contains an entry for this variant (Variation ID: 458676). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. For these reasons, this variant has been classified as Pathogenic. This sequence change replaces glycine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 324 of the ASS1 protein (p.Gly324Val). -

Citrullinemia type I Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Aug 28, 2023

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	34
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	1.0	D;D;D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.87
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.98	.;.;D
M_CAP	Pathogenic	0.75	D
MetaRNN	Pathogenic	1.0	D;D;D
MetaSVM	Pathogenic	0.89	D
MutationAssessor	Pathogenic	4.4	H;H;H
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.86	D
PROVEAN	Pathogenic	-8.8	D;D;D
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	D;D;D
Sift4G	Pathogenic	0.0010	D;D;D
Polyphen		1.0	D;D;D
Vest4		0.99
MutPred		0.99		Gain of helix (P = 0.2059);Gain of helix (P = 0.2059);Gain of helix (P = 0.2059);
MVP		0.99
MPC		1.0
ClinPred		1.0	D
GERP RS		4.8
Varity_R		0.99
gMVP		0.96

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.91
SpliceAI score (max)		0.080		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: rs1554725034; hg19: chr9-133370254;