rs886042070

chr9-34648850-G-A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000155.4(GALT):c.776G>A(p.Arg259Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,461,038 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R259W) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: GALT NM_000155.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:8 U:1
• Conservation: PhyloP100: 9.15

Genes affected

GALT (HGNC:4135): (galactose-1-phosphate uridylyltransferase) Galactose-1-phosphate uridyl transferase (GALT) catalyzes the second step of the Leloir pathway of galactose metabolism, namely the conversion of UDP-glucose + galactose-1-phosphate to glucose-1-phosphate + UDP-galactose. The absence of this enzyme results in classic galactosemia in humans and can be fatal in the newborn period if lactose is not removed from the diet. The pathophysiology of galactosemia has not been clearly defined. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Apr 2012]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 8 uncertain in NM_000155.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr9-34648849-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 189191.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.959
• PP5: Variant 9-34648850-G-A is Pathogenic according to our data. Variant chr9-34648850-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 280989.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GALT	NM_000155.4	c.776G>A	p.Arg259Gln	missense_variant	8/11	ENST00000378842.8
GALT	NM_001258332.2	c.449G>A	p.Arg150Gln	missense_variant	6/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GALT	ENST00000378842.8	c.776G>A	p.Arg259Gln	missense_variant	8/11	1	NM_000155.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461038 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 726878

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000712 Hom.: 0

Bravo AF: 0.0000151

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:8 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Deficiency of UDPglucose-hexose-1-phosphate uridylyltransferase Pathogenic:5 Uncertain:1

Uncertain significance, no assertion criteria provided	clinical testing	Counsyl	Mar 13, 2019	- -
Pathogenic, criteria provided, single submitter	clinical testing	DASA	Jun 10, 2022	The c.776G>A;p.(Arg259Gln) missense change has been observed in affected individual(s) and ClinVar contains an entry for this variant (Clinvar ID: 280989; PMID: 27603904; 23749220; 23418865; 22461411) - PS4. The variant is present at low allele frequencies population databases (rs886042070– gnomAD no frequency%; ABraOM 0.000427 frequency - http://abraom.ib.usp.br/) -PM2_supporting. The p.(Arg259Gln) was detected in trans with a Pathogenic variant (PMID: 23749220; 23418865; 22461411) - PM3. Pathogenic missense variant in this residue have been reported and classified as Pathogenic by ACMG criteria (Clinvar ID: 189191 - c.775C>T (p.Arg259Trp)) - PM5. Multiple lines of computational evidence support a deleterious effect on the gene or gene product - PP3. In summary, the currently available evidence indicates that the variant is Pathogenic -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	May 28, 2023	This variant disrupts the p.Arg259 amino acid residue in GALT. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 8741038, 11152465, 23749220). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Experimental studies have shown that this missense change affects GALT function (PMID: 22461411). 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 expected to disrupt GALT protein function. ClinVar contains an entry for this variant (Variation ID: 280989). This missense change has been observed in individual(s) with galactosemia (PMID: 22461411). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 259 of the GALT protein (p.Arg259Gln). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Mendelics	May 04, 2022	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Nov 01, 2016	Variant summary: The GALT c.776G>A (p.Arg259Gln) variant involves the alteration of a conserved nucleotide. 2/4 in silico tools predict a damaging outcome for this variant (SNPs&GO not captured due to low reliability index). This variant is absent in 121330 control chromosomes. This variant has been reported in at least two affected individuals via publications, and multiple clinical laboratories/reputable databases classified this variant as pathogenic/likely pathogenic. Functional study showed variant protein with no enzyme activity. Taken together, this variant is classified as likely pathogenic until more evidence becomes available. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Jul 15, 2023	- -

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jul 05, 2017	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Jun 17, 2018	The GALT c.776G>A; p.Arg259Gln variant (rs886042070) has been described in the compound heterozygous state in at least one individual with galactosemia, who has no detectable GALT enzyme activity in their red blood cells (Tang 2012). It is reported as likely pathogenic in ClinVar (Variation ID: 280989) and is absent from general population databases (1000 Genomes Project, Exome Variant Server, and Genome Aggregation Database), indicating it is not a common polymorphism. The arginine at codon 259 is highly conserved, but computational algorithms (PolyPhen-2: probably damaging, SIFT: tolerated) are inconclusive on the effect of this variant on protein structure and/or function. Another variant at this codon (c.775C>T; p.Arg259Trp) has been described in individuals with galactosemia and in vitro analysis of this variant protein demonstrates a significant reduction in GALT activity (Riehman 2001, Shin 1996). Based on available information, this variant is considered likely pathogenic. References: Riehman K et al. Relationship between genotype, activity, and galactose sensitivity in yeast expressing patient alleles of human galactose-1-phosphate uridylyltransferase. J Biol Chem. 2001 Apr 6;276(14):10634-40. Shin Y et al. Three missense mutations in the galactose-1-phosphate uridyltransferase gene of three families with mild galactosaemia. Eur J Pediatr. 1996 May;155(5):393-7. Tang M et al. Correlation assessment among clinical phenotypes, expression analysis and molecular modeling of 14 novel variations in the human galactose-1-phosphate uridylyltransferase gene. Hum Mutat. 2012 Jul;33(7):1107-15. -

Galactosemia Pathogenic:1

Likely pathogenic, no assertion criteria provided

clinical testing

Natera, Inc.

Sep 06, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.16
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.52
Cadd	Pathogenic	32
Dann	Pathogenic	1.0
Eigen	Pathogenic	0.83
Eigen_PC	Pathogenic	0.84
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D
M_CAP	Pathogenic	0.55	D
MetaRNN	Pathogenic	0.96	D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.58	T
PROVEAN	Uncertain	-2.6	D;N
REVEL	Pathogenic	0.92
Sift	Benign	0.52	T;T
Sift4G	Benign	0.15	T;T
Polyphen		1.0	.;D
Vest4		0.88
MutPred		0.83		.;Loss of MoRF binding (P = 0.0599);
MVP		1.0
MPC		1.3
ClinPred		0.99	D
GERP RS		5.8
Varity_R		0.48
gMVP		0.95

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs886042070; hg19: chr9-34648847;