22-30610970-A-C

Variant names:

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

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_000355.4(TCN2):​c.164A>C​(p.Tyr55Ser) 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 1,461,890 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. Y55C) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • 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: 2.84
• Publications: 1 publications found

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 Gene-Disease associations (from GenCC):

• transcobalamin II deficiency

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: G2P, Ambry Genetics, Labcorp Genetics (formerly Invitae), Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.958

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TCN2	NM_000355.4	c.164A>C	p.Tyr55Ser	missense_variant	Exon 2 of 9	ENST00000215838.8	NP_000346.2
TCN2	NM_001184726.2	c.164A>C	p.Tyr55Ser	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>C	p.Tyr55Ser	missense_variant	Exon 2 of 9	1	NM_000355.4	ENSP00000215838.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251488 AF XY: 0.00000736

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461890 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727244

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1112008

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Transcobalamin II deficiency Uncertain:1

Jun 06, 2024

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 serine, which is neutral and polar, at codon 55 of the TCN2 protein (p.Tyr55Ser). This variant is present in population databases (rs201701227, gnomAD 0.003%). This variant has not been reported in the literature in individuals affected with TCN2-related conditions. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt TCN2 protein function with a positive predictive value of 80%. 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	Pathogenic	0.59
BayesDel_addAF	Uncertain	0.14	D
BayesDel_noAF	Uncertain	0.070
CADD	Benign	23
DANN	Uncertain	0.99
DEOGEN2	Benign	0.19	T;T;T;.
Eigen	Uncertain	0.56
Eigen_PC	Uncertain	0.53
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Benign	0.75	T;T;T;T
M_CAP	Benign	0.041	D
MetaRNN	Pathogenic	0.96	D;D;D;D
MetaSVM	Benign	-0.46	T
MutationAssessor	Pathogenic	3.0	M;.;.;M
PhyloP100		2.8
PrimateAI	Uncertain	0.49	T
PROVEAN	Uncertain	-3.3	D;.;D;D
REVEL	Uncertain	0.33
Sift	Uncertain	0.0070	D;.;D;D
Sift4G	Uncertain	0.0020	D;D;D;D
Polyphen		1.0	D;.;D;.
Vest4		0.83
MutPred		0.86		Gain of disorder (P = 0.0102);.;Gain of disorder (P = 0.0102);Gain of disorder (P = 0.0102);
MVP		0.94
MPC		0.055
ClinPred		0.97	D
GERP RS		5.1
Varity_R		0.78
gMVP		0.57
Mutation Taster		=62/38	polymorphism

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

Other links and lift over

dbSNP: rs201701227; hg19: chr22-31006957;