22-30607348-C-A

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_000355.4(TCN2):c.17C>A(p.Ala6Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,864 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 (★). Synonymous variant affecting the same amino acid position (i.e. A6A) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TCN2 NM_000355.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -1.13

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 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.87

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TCN2	NM_000355.4	c.17C>A	p.Ala6Asp	missense_variant	1/9	ENST00000215838.8
TCN2	NM_001184726.2	c.17C>A	p.Ala6Asp	missense_variant	1/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TCN2	ENST00000215838.8	c.17C>A	p.Ala6Asp	missense_variant	1/9	1	NM_000355.4	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461864 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 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: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Transcobalamin II deficiency Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Aug 26, 2021

This sequence change replaces alanine with aspartic acid at codon 6 of the TCN2 protein (p.Ala6Asp). The alanine residue is moderately conserved and there is a moderate physicochemical difference between alanine and aspartic acid. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with TCN2-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). 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	Benign	0.22
BayesDel_addAF	Uncertain	0.13	D
BayesDel_noAF	Uncertain	-0.050
Cadd	Benign	16
Dann	Uncertain	0.99
DEOGEN2	Benign	0.11	T;T;.
Eigen	Benign	-0.17
Eigen_PC	Benign	-0.36
FATHMM_MKL	Benign	0.050	N
LIST_S2	Benign	0.48	T;T;T
M_CAP	Benign	0.0095	T
MetaRNN	Pathogenic	0.87	D;D;D
MetaSVM	Benign	-0.94	T
MutationAssessor	Uncertain	2.8	M;.;M
MutationTaster	Benign	1.0	N;N;N
PrimateAI	Benign	0.37	T
PROVEAN	Benign	-2.0	N;N;N
REVEL	Benign	0.26
Sift	Uncertain	0.013	D;D;D
Sift4G	Uncertain	0.021	D;D;D
Polyphen		0.96	D;D;.
Vest4		0.65
MutPred		0.75		Loss of helix (P = 0.028);Loss of helix (P = 0.028);Loss of helix (P = 0.028);
MVP		0.57
MPC		0.032
ClinPred		0.83	D
GERP RS		-0.020
Varity_R		0.21
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

No publications associated with this variant yet.

Other links and lift over

hg19: chr22-31003335;