2-227698738-C-G

Variant names:

• chr2-227698738-C-G
• rs747823282
• NM_025243.4:c.977G>C

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PM1 PM2

The NM_025243.4(SLC19A3):​c.977G>C​(p.Gly326Ala) variant causes a missense, splice region change. The variant was absent in control chromosomes in GnomAD project. 3/3 splice prediction tools predict no significant impact on normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G326V) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SLC19A3 NM_025243.4 missense, splice_region
• Scores: Splicing: ADA: 0.2913
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 4.06
• Publications: 0 publications found

Genes affected

SLC19A3 (HGNC:16266): (solute carrier family 19 member 3) This gene encodes a ubiquitously expressed transmembrane thiamine transporter that lacks folate transport activity. Mutations in this gene cause biotin-responsive basal ganglia disease (BBGD); a recessive disorder manifested in childhood that progresses to chronic encephalopathy, dystonia, quadriparesis, and death if untreated. Patients with BBGD have bilateral necrosis in the head of the caudate nucleus and in the putamen. Administration of high doses of biotin in the early progression of the disorder eliminates pathological symptoms while delayed treatment results in residual paraparesis, mild cognitive disability, or dystonia. Administration of thiamine is ineffective in the treatment of this disorder. Experiments have failed to show that this protein can transport biotin. Mutations in this gene also cause a Wernicke's-like encephalopathy.[provided by RefSeq, Jan 2010]

SLC19A3 Gene-Disease associations (from GenCC):

• biotin-responsive basal ganglia disease

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Orphanet, Genomics England PanelApp, G2P
• Leigh syndrome

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• infantile spams-psychomotor retardation-progressive brain atrophy-basal ganglia disease syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Leigh syndrome with leukodystrophy

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• thiamine-responsive encephalopathy

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 10 uncertain in NM_025243.4
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SLC19A3	NM_025243.4	c.977G>C	p.Gly326Ala	missense_variant, splice_region_variant	Exon 3 of 6	ENST00000644224.2	NP_079519.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SLC19A3	ENST00000644224.2	c.977G>C	p.Gly326Ala	missense_variant, splice_region_variant	Exon 3 of 6		NM_025243.4	ENSP00000495385.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000227

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.091
BayesDel_addAF	Uncertain	0.051	T
BayesDel_noAF	Benign	-0.16
CADD	Benign	18
DANN	Uncertain	1.0
DEOGEN2	Benign	0.11	T;T;.
Eigen	Uncertain	0.43
Eigen_PC	Uncertain	0.43
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.91	.;D;D
M_CAP	Benign	0.078	D
MetaRNN	Uncertain	0.58	D;D;D
MetaSVM	Uncertain	0.24	D
MutationAssessor	Uncertain	2.7	M;M;.
PhyloP100		4.1
PrimateAI	Benign	0.39	T
PROVEAN	Benign	0.40	.;N;.
REVEL	Uncertain	0.43
Sift	Benign	0.25	.;T;.
Sift4G	Benign	0.35	.;T;.
Polyphen		0.77	P;P;.
Vest4		0.31
MutPred		0.58		Loss of catalytic residue at G327 (P = 0.1851);Loss of catalytic residue at G327 (P = 0.1851);.;
MVP		0.94
MPC		0.30
ClinPred		0.86	D
GERP RS		4.9
Varity_R		0.069
gMVP		0.32
Mutation Taster		=84/16	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.29
dbscSNV1_RF	Benign	0.48
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

Other links and lift over

dbSNP: rs747823282; hg19: chr2-228563454;