12-102839216-C-A

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1_Strong PM2 PP5_Very_Strong

The NM_000277.3(PAH):c.1318G>T(p.Glu440Ter) variant causes a stop gained, splice region change. The variant allele was found at a frequency of 0.000000684 in 1,461,530 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 1/1 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: PAH NM_000277.3 stop_gained, splice_region
• Clinical Significance: Likely pathogenic reviewed by expert panel P:1
• Conservation: PhyloP100: 5.92

Genes affected

PAH (HGNC:8582): (phenylalanine hydroxylase) This gene encodes a member of the biopterin-dependent aromatic amino acid hydroxylase protein family. The encoded phenylalanine hydroxylase enzyme hydroxylates phenylalanine to tyrosine and is the rate-limiting step in phenylalanine catabolism. Deficiency of this enzyme activity results in the autosomal recessive disorder phenylketonuria. [provided by RefSeq, Aug 2017]

ACMG classification

Verdict is Pathogenic. Variant got 14 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. There are 9 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 12-102839216-C-A is Pathogenic according to our data. Variant chr12-102839216-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 932274.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr12-102839216-C-A is described in Lovd as [Pathogenic]. Variant chr12-102839216-C-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
PAH	NM_000277.3	c.1318G>T	p.Glu440Ter	stop_gained, splice_region_variant	13/13	ENST00000553106.6
PAH	NM_001354304.2	c.1318G>T	p.Glu440Ter	stop_gained, splice_region_variant	14/14

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
PAH	ENST00000553106.6	c.1318G>T	p.Glu440Ter	stop_gained, splice_region_variant	13/13	1	NM_000277.3	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461530 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 727076

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: reviewed by expert panel

Submissions by phenotype

Phenylketonuria Pathogenic:1

Likely pathogenic, reviewed by expert panel

curation

ClinGen PAH Variant Curation Expert Panel

May 15, 2020

The c.1318G>T (p.E440*) is a nonsense variant in exon 13 of 13 of PAH, a gene where loss of function is a known disease mechanism, and is predicted to lead to premature truncation of the protein at amino acid 440/453 (PVS1_Strong). Exon 13 encodes 15 amino acids + stop codon = 3.3% of PAH protein length. Along with Exon 12, Exon 13 forms the oligomerization domain (residues 411-452), which is responsible for the dimerization and tetramerization of the enzyme, important for regulation of PAH activity (e.g., positive cooperativity by the substrate, L-Phe, and decreasing PAH activity at low L-Phe concentration) (see PMID: 23457044; PMID: 22005392). Exon 13 contains the non-truncating Likely Pathogenic p.A447P (Likely Pathogenic by ClinGen PAH VCEP) and Pathogenic p.A447D variants (Likely Pathogenic by ClinGen PAH VCEP; Pathogenic in Clinvar (ID 102595; 4 submitters, 2 stars). Thus PVS1_Strong will be applied for variants resulting in premature truncation of this exon. The variant is absent from ethnically diverse control databases, including gnomAD/ExAC, 1000 Genomes, and ESP (PM2). It has been previously reported in one proband with abnormal blood Phe (BH4 deficiency does not appear to have been formally excluded) (PP4) (PMID: 23842451), in presumed trans with the p.R243* mutation (Pathogenic per PAH VCEP) (0.5 points; PM3_Supporting). Classification: Likely Pathogenic Supporting Criteria: PVS1_Strong; PM2; PM3_Supporting; PP4 -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.62	D
BayesDel_noAF	Pathogenic	0.65
Cadd	Pathogenic	56
Dann	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.96
FATHMM_MKL	Pathogenic	0.98	D
MutationTaster	Benign	1.0	D;D
Vest4		0.78
GERP RS		5.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs1874485021; hg19: chr12-103232994;