rs1554709252

chr9-34647674-C-Achr9-34647674-C-G

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP3_Moderate

The NM_000155.4(GALT):c.346C>A(p.Leu116Ile) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,880 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 Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L116V) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: GALT NM_000155.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 1.22

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 Likely_pathogenic. Variant got 8 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, 3 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 chr9-34647675-T-C is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.937

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GALT	NM_000155.4	c.346C>A	p.Leu116Ile	missense_variant	4/11	ENST00000378842.8
GALT	NM_001258332.2	c.51-158C>A		intron_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GALT	ENST00000378842.8	c.346C>A	p.Leu116Ile	missense_variant	4/11	1	NM_000155.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461880 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727238

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000504

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Nov 07, 2023

Variant summary: GALT c.346C>A (p.Leu116Ile) results in a conservative amino acid change located in the Galactose-1-phosphate uridyl transferase, N-terminal (IPR005849) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251440 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.346C>A has been reported at a compound heterozygous state with a second pathogenic variant in at-least one individual affected with Galactosemia (Ko_2010). This variant has also been reported at a heterozygous state in one individual affected with Galactosemia without second variant in GALT (Choi_2014). These data do not allow any conclusion about variant significance. At least one publication reports experimental evidence evaluating an impact on protein function. These results showed no damaging effect of this variant as the variant produced similar GALT activities as in the WT control in T293 cells (Ko_2010). The following publications have been ascertained in the context of this evaluation (PMID: 25124065, 20547145). One submitter has cited clinical-significance assessments for this variant to ClinVar after 2014 and has classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as uncertain significance. -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Counsyl

Nov 07, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.20
BayesDel_addAF	Pathogenic	0.29	D
BayesDel_noAF	Pathogenic	0.18
Cadd	Uncertain	26
Dann	Uncertain	0.99
DEOGEN2	Uncertain	0.79	D
Eigen	Uncertain	0.55
Eigen_PC	Uncertain	0.44
FATHMM_MKL	Uncertain	0.81	D
LIST_S2	Uncertain	0.93	D
M_CAP	Pathogenic	0.47	D
MetaRNN	Pathogenic	0.94	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.8	H
MutationTaster	Benign	1.0	D;D
PrimateAI	Benign	0.47	T
PROVEAN	Benign	-1.8	N
REVEL	Pathogenic	0.90
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.020	D
Polyphen		0.92	P
Vest4		0.57
MutPred		0.88		Loss of catalytic residue at L116 (P = 0.0205);
MVP		0.99
MPC		1.8
ClinPred		0.99	D
GERP RS		4.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.88
gMVP		0.83

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.070		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: rs1554709252; hg19: chr9-34647671;