rs748666093

Variant names:

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PM1PM2PP2

The NM_000161.3(GCH1):c.230C>G(p.Ser77Cys) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,460,720 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★).

Frequency

Genomes: not found (cov: 33)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

GCH1
NM_000161.3 missense

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 4.20

Publications

1 publications found

Variant links:

Genes affected

GCH1 (HGNC:4193): (GTP cyclohydrolase 1) This gene encodes a member of the GTP cyclohydrolase family. The encoded protein is the first and rate-limiting enzyme in tetrahydrobiopterin (BH4) biosynthesis, catalyzing the conversion of GTP into 7,8-dihydroneopterin triphosphate. BH4 is an essential cofactor required by aromatic amino acid hydroxylases as well as nitric oxide synthases. Mutations in this gene are associated with malignant hyperphenylalaninemia and dopa-responsive dystonia. Several alternatively spliced transcript variants encoding different isoforms have been described; however, not all variants give rise to a functional enzyme. [provided by RefSeq, Jul 2008]

GCH1 Gene-Disease associations (from GenCC):

dystonia 5
Inheritance: AD, AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Orphanet, Genomics England PanelApp, Labcorp Genetics (formerly Invitae), G2P
GTP cyclohydrolase I deficiency with hyperphenylalaninemia
Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, Orphanet, G2P
GTP cyclohydrolase I deficiency
Inheritance: SD, AD Classification: DEFINITIVE Submitted by: ClinGen, Illumina

GCH1 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

PM1

In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 6 uncertain in NM_000161.3

PM2

Very rare variant in population databases, with high coverage;

PP2

Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 30 curated pathogenic missense variants (we use a threshold of 10). The gene has 1 curated benign missense variants. Gene score misZ: 1.5191 (below the threshold of 3.09). Trascript score misZ: 0.62455 (below the threshold of 3.09). GenCC associations: The gene is linked to GTP cyclohydrolase I deficiency, dystonia 5, GTP cyclohydrolase I deficiency with hyperphenylalaninemia.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GCH1	NM_000161.3 link	c.230C>G	p.Ser77Cys	missense_variant	Exon 1 of 6	ENST00000491895.7	NP_000152.1	P30793-1A0A024R642

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GCH1	ENST00000491895.7 link	c.230C>G	p.Ser77Cys	missense_variant	Exon 1 of 6	1	NM_000161.3	ENSP00000419045.2		P30793-1

Frequencies

GnomAD3 genomes

Cov.:

GnomAD2 exomes

AF:

0.00000402

AC:

AN:

248812

AF XY:

0.00000739

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000547

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000137

AC:

AN:

1460720

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

726704

show subpopulations

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

33462

American (AMR)

AF:

0.00

AC:

AN:

44702

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26114

East Asian (EAS)

AF:

0.0000252

AC:

AN:

39684

South Asian (SAS)

AF:

0.00

AC:

AN:

86222

European-Finnish (FIN)

AF:

0.00

AC:

AN:

52642

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5748

European-Non Finnish (NFE)

AF:

8.99e-7

AC:

AN:

1111794

Other (OTH)

AF:

0.00

AC:

AN:

60352

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.00000000770867), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.400

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

Cov.:

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.0000113

ExAC

AF:

0.00000824

AC:

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

GTP cyclohydrolase I deficiency;C1851920:Dystonia 5

Uncertain:1

Jan 10, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces serine, which is neutral and polar, with cysteine, which is neutral and slightly polar, at codon 77 of the GCH1 protein (p.Ser77Cys). This variant is present in population databases (rs748666093, gnomAD 0.006%). This missense change has been observed in individual(s) with clinical features of GCH1-related conditions (Invitae). ClinVar contains an entry for this variant (Variation ID: 577041). 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) performed at Invitae indicates that this missense variant is not expected to disrupt GCH1 protein function with a negative predictive value of 80%. 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. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.084

BayesDel_addAF

Uncertain

0.081

BayesDel_noAF

Uncertain

0.050

CADD

Uncertain

(source)

DANN

Benign

0.96

DEOGEN2

Pathogenic

0.95

D;D;.;D;.

Eigen

Benign

-0.22

Eigen_PC

Benign

-0.15

FATHMM_MKL

Benign

0.69

LIST_S2

Uncertain

0.89

.;D;D;.;D

M_CAP

Pathogenic

0.87

MetaRNN

Uncertain

0.44

T;T;T;T;T

MetaSVM

Pathogenic

1.1

MutationAssessor

Pathogenic

3.2

M;M;M;M;M

PhyloP100

4.2

PrimateAI

Uncertain

0.65

PROVEAN

Benign

-2.1

.;N;D;N;D

REVEL

Uncertain

0.55

Sift

Uncertain

0.0080

.;D;D;D;D

Sift4G

Uncertain

0.025

D;D;D;D;D

Polyphen

0.037

B;B;B;B;B

Vest4

0.27

MutPred

0.41

Loss of disorder (P = 0.0059);Loss of disorder (P = 0.0059);Loss of disorder (P = 0.0059);Loss of disorder (P = 0.0059);Loss of disorder (P = 0.0059);

MVP

0.88

MPC

1.0

ClinPred

0.55

GERP RS

3.7

PromoterAI

-0.14

Neutral

(source)

Varity_R

0.90

gMVP

0.70

Mutation Taster

=50/50

(source)

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over