chr20-4699225-C-T

Variant names:

• chr20-4699225-C-T
• rs748227837
• NM_000311.5:c.5C>T

Variant summary

Our verdict is Benign. The variant received -7 ACMG points: 0P and 7B. BP4_Moderate BP6 BS2

The NM_000311.5(PRNP):​c.5C>T​(p.Ala2Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000186 in 1,613,912 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 17/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. A2A) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000026 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000018 (0 hom.)
• Consequence: PRNP NM_000311.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:1
• Conservation: PhyloP100: 0.125

Genes affected

PRNP (HGNC:9449): (prion protein (Kanno blood group)) The protein encoded by this gene is a membrane glycosylphosphatidylinositol-anchored glycoprotein that tends to aggregate into rod-like structures. The encoded protein contains a highly unstable region of five tandem octapeptide repeats. This gene is found on chromosome 20, approximately 20 kbp upstream of a gene which encodes a biochemically and structurally similar protein to the one encoded by this gene. Mutations in the repeat region as well as elsewhere in this gene have been associated with Creutzfeldt-Jakob disease, fatal familial insomnia, Gerstmann-Straussler disease, Huntington disease-like 1, and kuru. An overlapping open reading frame has been found for this gene that encodes a smaller, structurally unrelated protein, AltPrp. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Nov 2014]

ACMG classification

Our verdict: Benign. The variant received -7 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.14240313).
• BP6: Variant 20-4699225-C-T is Benign according to our data. Variant chr20-4699225-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 899176.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=1, Uncertain_significance=1}.
• BS2: High AC in GnomAdExome4 at 26 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PRNP	NM_000311.5	c.5C>T	p.Ala2Val	missense_variant	Exon 2 of 2	ENST00000379440.9	NP_000302.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
PRNP	ENST00000379440.9	c.5C>T	p.Ala2Val	missense_variant	Exon 2 of 2	1	NM_000311.5	ENSP00000368752.4
PRNP	ENST00000424424.2	c.5C>T	p.Ala2Val	missense_variant	Exon 2 of 2	1		ENSP00000411599.2
PRNP	ENST00000430350.2	c.5C>T	p.Ala2Val	missense_variant	Exon 2 of 2	1		ENSP00000399376.2
PRNP	ENST00000457586.2	c.5C>T	p.Ala2Val	missense_variant	Exon 2 of 2	1		ENSP00000415284.2

Frequencies

GnomAD3 genomes AF: 0.0000263 AC: 4 AN: 152210 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000483

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000294

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.0000241 AC: 6 AN: 249204 AF XY: 0.0000222

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.0000545

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000446

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000178 AC: 26 AN: 1461702 Hom.: 0 Cov.: 31 AF XY: 0.0000193 AC XY: 14 AN XY: 727168

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53234

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.0000234 AC: 26 AN: 1112006

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome AF: 0.0000263 AC: 4 AN: 152210 Hom.: 0 Cov.: 32 AF XY: 0.0000134 AC XY: 1 AN XY: 74364

African (AFR) AF: 0.0000483 AC: 2 AN: 41444

American (AMR) AF: 0.00 AC: 0 AN: 15278

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5198

South Asian (SAS) AF: 0.00 AC: 0 AN: 4834

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10622

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000294 AC: 2 AN: 68042

Other (OTH) AF: 0.00 AC: 0 AN: 2094

Alfa AF: 0.0000860 Hom.: 0

Bravo AF: 0.0000227

ExAC AF: 0.0000247 AC: 3

EpiCase AF: 0.000109

EpiControl AF: 0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Huntington disease-like 1 Uncertain:1

Mar 27, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 2 of the PRNP protein (p.Ala2Val). This variant is present in population databases (rs748227837, gnomAD 0.006%). This variant has not been reported in the literature in individuals affected with PRNP-related conditions. ClinVar contains an entry for this variant (Variation ID: 899176). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Not Available"; PolyPhen-2: "Benign"; Align-GVGD: "Not Available". The valine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Inherited prion disease Benign:1

Jun 28, 2017

Illumina Laboratory Services, Illumina

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). No publications were found based on this search. Allele frequency data from public databases allowed determination this variant is unlikely to cause disease. Therefore, this variant is classified as likely benign. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.16
BayesDel_addAF	Benign	-0.17	T
BayesDel_noAF	Benign	-0.31
CADD	Benign	10
DANN	Benign	0.88
DEOGEN2	Benign	0.016	T;T;T;.
Eigen	Benign	-0.97
Eigen_PC	Benign	-0.99
FATHMM_MKL	Benign	0.022	N
LIST_S2	Benign	0.68	.;T;T;T
M_CAP	Benign	0.036	D
MetaRNN	Benign	0.14	T;T;T;T
MetaSVM	Uncertain	-0.14	T
MutationAssessor	Benign	0.90	L;L;.;.
PhyloP100		0.13
PrimateAI	Benign	0.32	T
PROVEAN	Benign	-0.91	N;N;N;N
REVEL	Benign	0.16
Sift	Benign	0.050	D;D;T;D
Sift4G	Benign	0.12	T;T;T;T
Polyphen		0.0070	B;B;.;.
Vest4		0.057
MVP		0.99
MPC		0.50
ClinPred		0.016	T
GERP RS		-0.28
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0
Varity_R		0.035
gMVP		0.15
Mutation Taster		=93/7	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Publications

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Other links and lift over

dbSNP: rs748227837; hg19: chr20-4679871; COSMIC: COSV108235716;