rs760206323

Positions:

• chr3-120633146-C-A
• chr3-120633146-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000187.4(HGD):​c.1188+1G>T variant causes a splice donor change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000616 in 1,461,738 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000062 (0 hom.)
• Consequence: HGD NM_000187.4 splice_donor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 7.36

Genes affected

HGD (HGNC:4892): (homogentisate 1,2-dioxygenase) This gene encodes the enzyme homogentisate 1,2 dioxygenase. This enzyme is involved in the catabolism of the amino acids tyrosine and phenylalanine. Mutations in this gene are the cause of the autosomal recessive metabolism disorder alkaptonuria.[provided by RefSeq, May 2010]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 4.6, offset of 4, new splice context is: taaGTatgt. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-120633146-C-A is Pathogenic according to our data. Variant chr3-120633146-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 370979.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr3-120633146-C-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HGD	NM_000187.4	c.1188+1G>T		splice_donor_variant		ENST00000283871.10	NP_000178.2
HGD	XM_005247412.3	c.963+1G>T		splice_donor_variant			XP_005247469.1
HGD	XM_017006277.3	c.765+1G>T		splice_donor_variant			XP_016861766.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HGD	ENST00000283871.10	c.1188+1G>T		splice_donor_variant		1	NM_000187.4	ENSP00000283871	P1
HGD	ENST00000492108.5	c.*170+1G>T		splice_donor_variant, NMD_transcript_variant		2		ENSP00000419838
HGD	ENST00000470321.1			downstream_gene_variant		3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000160 AC: 4 AN: 250658 Hom.: 0 AF XY: 0.00000738 AC XY: 1 AN XY: 135474

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000354

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000616 AC: 9 AN: 1461738 Hom.: 0 Cov.: 32 AF XY: 0.00000550 AC XY: 4 AN XY: 727182

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: 0.00000719

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ExAC AF: 0.0000247 AC: 3

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Alkaptonuria Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jul 16, 2020	For these reasons, this variant has been classified as Pathogenic. This variant disrupts the C-terminus of the HGD protein. Other variant(s) that disrupt this region (p.Lys431Hisfs*11) have been determined to be pathogenic (PMID: 23430897, 25681086, Invitae). This suggests that variants that disrupt this region of the protein are likely to be causative of disease. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. This variant has been observed in individual(s) with alkaptonuria (PMID: 11001939). ClinVar contains an entry for this variant (Variation ID: 370979). This variant is present in population databases (rs760206323, ExAC 0.005%). This sequence change affects a donor splice site in the last intron (intron 13) of the HGD gene. While this is not anticipated to result in nonsense mediated decay, it likely alters RNA splicing and results in a disrupted protein product. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	May 26, 2016	- -
Pathogenic, no assertion criteria provided	research	Department Of Human Genetics, Institute Of Clinical And Translational Research, Biomedical Research Center, Slovak Academy Of Sciences	-	The variant was originally described in AKU patient in PMID:11001939. It has been submitted to the HGD gene mutation database (http://hgddatabase.cvtisr.sk/, DB-ID: AKU_00101). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.29
CADD	Pathogenic	33
DANN	Uncertain	0.99
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.88
FATHMM_MKL	Pathogenic	0.98	D
MutationTaster	Benign	1.0	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.8

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.92
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.21		Position offset: -3
DS_DL_spliceai		0.99		Position offset: 1

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

Publications

LitVar

Other links and lift over

dbSNP: rs760206323; hg19: chr3-120351993;