14-54842973-C-T

Variant summary

Our verdict is Benign. Variant got -7 ACMG points: 2P and 9B. PM2 BP4_Strong BP6 BS1

The NM_000161.3(GCH1):c.*1044G>A variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000367 in 749,840 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00087 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00024 (0 hom.)
• Consequence: GCH1 NM_000161.3 3_prime_UTR
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:1
• Conservation: PhyloP100: 0.121

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]

ACMG classification

Verdict is Benign. Variant got -7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.8).
• BP6: Variant 14-54842973-C-T is Benign according to our data. Variant chr14-54842973-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 883618.We mark this variant Likely_benign, oryginal submissions are: {Uncertain_significance=1, Benign=1}.
• BS1: Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.000867 (132/152240) while in subpopulation AFR AF= 0.00272 (113/41528). AF 95% confidence interval is 0.00231. There are 0 homozygotes in gnomad4. There are 72 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GCH1	NM_000161.3	c.*1044G>A		3_prime_UTR_variant	6/6	ENST00000491895.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GCH1	ENST00000491895.7	c.*1044G>A		3_prime_UTR_variant	6/6	1	NM_000161.3	P1

Frequencies

GnomAD3 genomes AF: 0.000822 AC: 125 AN: 152122 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00256

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000328

Gnomad ASJ AF: 0.00230

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000882

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.000239 AC: 143 AN: 597600 Hom.: 0 Cov.: 6 AF XY: 0.000228 AC XY: 74 AN XY: 324310

Gnomad4 AFR exome AF: 0.00222

Gnomad4 AMR exome AF: 0.000193

Gnomad4 ASJ exome AF: 0.00345

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000674

Gnomad4 OTH exome AF: 0.000283

GnomAD4 genome AF: 0.000867 AC: 132 AN: 152240 Hom.: 0 Cov.: 32 AF XY: 0.000967 AC XY: 72 AN XY: 74428

Gnomad4 AFR AF: 0.00272

Gnomad4 AMR AF: 0.000327

Gnomad4 ASJ AF: 0.00230

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000882

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000832 Hom.: 0

Bravo AF: 0.00101

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

GTP cyclohydrolase I deficiency Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Dystonia 5 Benign:1

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.80
Cadd	Benign	8.1
Dann	Benign	0.60

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: rs143961472; hg19: chr14-55309691;