rs75680863

Positions:

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2PP3

The NM_000355.4(TCN2):c.230A>G(p.Lys77Arg) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000124 in 1,613,958 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. K77M) has been classified as Benign.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 33)

Exomes 𝑓: 6.8e-7 ( 0 hom. )

Consequence

TCN2
NM_000355.4 missense

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 1.38

Variant links:

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]

TCN2 links:

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ACMG classification

Classification made for transcript

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, 0.772

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TCN2	NM_000355.4 linkuse as main transcript	c.230A>G	p.Lys77Arg	missense_variant	2/9	ENST00000215838.8
TCN2	NM_001184726.2 linkuse as main transcript	c.230A>G	p.Lys77Arg	missense_variant	2/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TCN2	ENST00000215838.8 linkuse as main transcript	c.230A>G	p.Lys77Arg	missense_variant	2/9	1	NM_000355.4	P2	P20062-1

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152132

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000241

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD4 exome

AF:

6.84e-7

AC:

AN:

1461826

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

727218

show subpopulations

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:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152132

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74328

show subpopulations

Gnomad4 AFR

AF:

0.0000241

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

Bravo

AF:

0.0000151

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

Transcobalamin II deficiency

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 24, 2021

This sequence change replaces lysine with arginine at codon 77 of the TCN2 protein (p.Lys77Arg). The lysine residue is highly conserved and there is a small physicochemical difference between lysine and arginine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals 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: "Tolerated"; 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

0.13

BayesDel_addAF

Benign

-0.15

BayesDel_noAF

Benign

-0.46

CADD

Benign

DANN

Uncertain

1.0

DEOGEN2

Benign

0.10

T;T;T;.

Eigen

Uncertain

0.52

Eigen_PC

Uncertain

0.49

FATHMM_MKL

Uncertain

0.85

LIST_S2

Benign

0.77

T;T;T;T

M_CAP

Benign

0.028

MetaRNN

Pathogenic

0.77

D;D;D;D

MetaSVM

Benign

-0.67

MutationAssessor

Pathogenic

3.1

M;.;.;M

MutationTaster

Benign

1.0

D;D;D

PrimateAI

Uncertain

0.49

PROVEAN

Benign

-1.4

N;.;N;N

REVEL

Benign

0.25

Sift

Uncertain

0.022

D;.;D;T

Sift4G

Benign

0.23

T;T;T;T

Polyphen

0.99

D;.;D;.

Vest4

0.46

MutPred

0.83

Loss of ubiquitination at K77 (P = 0.0127);.;Loss of ubiquitination at K77 (P = 0.0127);Loss of ubiquitination at K77 (P = 0.0127);

MVP

0.77

MPC

0.026

ClinPred

0.97

GERP RS

5.1

Varity_R

0.34

gMVP

0.40

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over