22-30610970-A-G

Variant names:

• chr22-30610970-A-G
• rs201701227
• NM_000355.4:c.164A>G

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_000355.4(TCN2):​c.164A>G​(p.Tyr55Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000589 in 1,614,040 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 (★).

• Frequency:
  • Genomes: 𝑓 0.000099 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000055 (0 hom.)
• Consequence: TCN2 NM_000355.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.84

Genes affected

TCN2 (HGNC:11653): (transcobalamin 2) This gene encodes a member of the vitamin B12-binding protein family. This family of proteins, alternatively referred to as R binders, is expressed in various tissues and secretions. This plasma protein binds cobalamin and mediates the transport of cobalamin into cells. This protein and other mammalian cobalamin-binding proteins, such as transcobalamin I and gastric intrisic factor, may have evolved by duplication of a common ancestral gene. Alternative splicing results in multiple transcript variants.[provided by RefSeq, May 2010]

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.782

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TCN2	NM_000355.4	c.164A>G	p.Tyr55Cys	missense_variant	Exon 2 of 9	ENST00000215838.8	NP_000346.2
TCN2	NM_001184726.2	c.164A>G	p.Tyr55Cys	missense_variant	Exon 2 of 9		NP_001171655.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TCN2	ENST00000215838.8	c.164A>G	p.Tyr55Cys	missense_variant	Exon 2 of 9	1	NM_000355.4	ENSP00000215838.3

Frequencies

GnomAD3 genomes AF: 0.0000986 AC: 15 AN: 152150 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000131

Gnomad ASJ AF: 0.000865

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000103

Gnomad OTH AF: 0.000957

GnomAD3 exomes AF: 0.0000875 AC: 22 AN: 251488 Hom.: 0 AF XY: 0.0000956 AC XY: 13 AN XY: 135922

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000260

Gnomad ASJ exome AF: 0.000397

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.0000462

Gnomad NFE exome AF: 0.0000527

Gnomad OTH exome AF: 0.000326

GnomAD4 exome AF: 0.0000547 AC: 80 AN: 1461890 Hom.: 0 Cov.: 32 AF XY: 0.0000646 AC XY: 47 AN XY: 727244

Gnomad4 AFR exome AF: 0.0000597

Gnomad4 AMR exome AF: 0.000291

Gnomad4 ASJ exome AF: 0.000383

Gnomad4 EAS exome AF: 0.0000504

Gnomad4 SAS exome AF: 0.0000348

Gnomad4 FIN exome AF: 0.0000374

Gnomad4 NFE exome AF: 0.0000378

Gnomad4 OTH exome AF: 0.0000993

GnomAD4 genome AF: 0.0000986 AC: 15 AN: 152150 Hom.: 0 Cov.: 33 AF XY: 0.000121 AC XY: 9 AN XY: 74314

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.000131

Gnomad4 ASJ AF: 0.000865

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000103

Gnomad4 OTH AF: 0.000957

Alfa AF: 0.0000931 Hom.: 0

Bravo AF: 0.0000945

ExAC AF: 0.0000576 AC: 7

EpiCase AF: 0.000164

EpiControl AF: 0.000119

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Transcobalamin II deficiency Uncertain:1

Aug 31, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces tyrosine, which is neutral and polar, with cysteine, which is neutral and slightly polar, at codon 55 of the TCN2 protein (p.Tyr55Cys). This variant is present in population databases (rs201701227, gnomAD 0.04%). This variant has not been reported in the literature in individuals affected with TCN2-related conditions. ClinVar contains an entry for this variant (Variation ID: 573502). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.47
BayesDel_addAF	Benign	-0.043	T
BayesDel_noAF	Uncertain	0.020
CADD	Uncertain	23
DANN	Uncertain	1.0
DEOGEN2	Benign	0.19	T;T;T;.
Eigen	Uncertain	0.57
Eigen_PC	Uncertain	0.54
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Benign	0.84	T;D;T;T
M_CAP	Benign	0.036	D
MetaRNN	Pathogenic	0.78	D;D;D;D
MetaSVM	Benign	-0.44	T
MutationAssessor	Pathogenic	3.0	M;.;.;M
PrimateAI	Uncertain	0.55	T
PROVEAN	Uncertain	-3.9	D;.;D;D
REVEL	Uncertain	0.36
Sift	Uncertain	0.0030	D;.;D;D
Sift4G	Pathogenic	0.0010	D;D;D;D
Polyphen		1.0	D;.;D;.
Vest4		0.86
MVP		0.92
MPC		0.057
ClinPred		0.88	D
GERP RS		5.1
Varity_R		0.71
gMVP		0.54

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: rs201701227; hg19: chr22-31006957;