22-30607350-T-C

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_000355.4(TCN2):c.19T>C(p.Phe7Leu) 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 1,461,876 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. F7F) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 31)
  • 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: 0.174

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 Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.026195437).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TCN2	NM_000355.4	c.19T>C	p.Phe7Leu	missense_variant	1/9	ENST00000215838.8
TCN2	NM_001184726.2	c.19T>C	p.Phe7Leu	missense_variant	1/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TCN2	ENST00000215838.8	c.19T>C	p.Phe7Leu	missense_variant	1/9	1	NM_000355.4	P2

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461876 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727246

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

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

Sep 14, 2022

This sequence change replaces phenylalanine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 7 of the TCN2 protein (p.Phe7Leu). This variant is not present in population databases (gnomAD 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 output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The leucine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. 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	0.28
BayesDel_addAF	Benign	-0.17	T
BayesDel_noAF	Benign	-0.48
Cadd	Benign	12
Dann	Benign	0.88
DEOGEN2	Benign	0.019	T;T;.
Eigen	Benign	-1.3
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.0074	N
LIST_S2	Benign	0.37	T;T;T
M_CAP	Benign	0.0054	T
MetaRNN	Benign	0.026	T;T;T
MetaSVM	Benign	-0.91	T
MutationAssessor	Benign	-0.84	N;.;N
MutationTaster	Benign	1.0	N;N;N
PrimateAI	Benign	0.39	T
PROVEAN	Benign	1.6	N;N;N
REVEL	Benign	0.096
Sift	Benign	1.0	T;T;T
Sift4G	Benign	1.0	T;T;T
Polyphen		0.0010	B;B;.
Vest4		0.084
MutPred		0.59		Gain of disorder (P = 0.1365);Gain of disorder (P = 0.1365);Gain of disorder (P = 0.1365);
MVP		0.076
MPC		0.0091
ClinPred		0.046	T
GERP RS		-0.16
Varity_R		0.042
gMVP		0.11

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: chr22-31003337;