NM_000355.4:c.921A>C

Variant names:

• chr22-30615768-A-C
• rs138738105
• NM_000355.4:c.921A>C

Variant summary

Our verdict is Benign. Variant got -8 ACMG points: 2P and 10B. PM2 BP4_Strong BP6 BP7 BS1

The NM_000355.4(TCN2):​c.921A>C​(p.Pro307Pro) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000294 in 1,614,210 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00016 (0 hom., cov: 33)
  • Exomes 𝑓: 0.00031 (1 hom.)
• Consequence: TCN2 NM_000355.4 synonymous
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:5
• Conservation: PhyloP100: 1.39

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 Benign. Variant got -8 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.61).
• BP6: Variant 22-30615768-A-C is Benign according to our data. Variant chr22-30615768-A-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 341206.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=3, Uncertain_significance=1}. Variant chr22-30615768-A-C is described in Lovd as [Likely_benign].
• BP7: Synonymous conserved (PhyloP=1.39 with no splicing effect.
• BS1: Variant frequency is greater than expected in population sas. gnomad4 allele frequency = 0.000164 (25/152322) while in subpopulation SAS AF= 0.00207 (10/4832). AF 95% confidence interval is 0.00112. There are 0 homozygotes in gnomad4. There are 17 alleles in male gnomad4 subpopulation. Median coverage is 33. This position pass quality control queck.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TCN2	NM_000355.4	c.921A>C	p.Pro307Pro	synonymous_variant	Exon 6 of 9	ENST00000215838.8	NP_000346.2
TCN2	NM_001184726.2	c.840A>C	p.Pro280Pro	synonymous_variant	Exon 6 of 9		NP_001171655.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TCN2	ENST00000215838.8	c.921A>C	p.Pro307Pro	synonymous_variant	Exon 6 of 9	1	NM_000355.4	ENSP00000215838.3

Frequencies

GnomAD3 genomes AF: 0.000164 AC: 25 AN: 152204 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000131

Gnomad ASJ AF: 0.000288

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00207

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000162

Gnomad OTH AF: 0.000478

GnomAD3 exomes AF: 0.000354 AC: 89 AN: 251470 Hom.: 0 AF XY: 0.000441 AC XY: 60 AN XY: 135904

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000231

Gnomad ASJ exome AF: 0.0000992

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00157

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000255

Gnomad OTH exome AF: 0.000489

GnomAD4 exome AF: 0.000307 AC: 449 AN: 1461888 Hom.: 1 Cov.: 35 AF XY: 0.000380 AC XY: 276 AN XY: 727244

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.000246

Gnomad4 ASJ exome AF: 0.000191

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00212

Gnomad4 FIN exome AF: 0.0000187

Gnomad4 NFE exome AF: 0.000186

Gnomad4 OTH exome AF: 0.000464

GnomAD4 genome AF: 0.000164 AC: 25 AN: 152322 Hom.: 0 Cov.: 33 AF XY: 0.000228 AC XY: 17 AN XY: 74486

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.000131

Gnomad4 ASJ AF: 0.000288

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00207

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000162

Gnomad4 OTH AF: 0.000473

Alfa AF: 0.000223 Hom.: 0

Bravo AF: 0.000117

Asia WGS AF: 0.000289 AC: 1 AN: 3478

EpiCase AF: 0.000109

EpiControl AF: 0.000356

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:5

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Benign:4

-

Genome Diagnostics Laboratory, University Medical Center Utrecht

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

-

Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Feb 01, 2023

CeGaT Center for Human Genetics Tuebingen

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

TCN2: BP4, BP7 -

Dec 04, 2017

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.Pro307Pro variant (rs138738105) does not alter the amino acid sequence of the TCN2 protein and computational splice site prediction algorithms do not predict a change in the nearest splice site or creation of a cryptic splice site (Alamut v2.10). This variant has not been reported in association with megaloblastic anemia in medical literature or in gene specific variation databases. This variant is listed in the Genome Aggregation Database (gnomAD) with a frequency of 0.2 percent in the South Asian population (identified on 49 out of 30,782 chromosomes), and has been reported to the ClinVar database (Variation ID: 341206). Based on these observations, the p.Pro307Pro variant is likely to be benign. -

Transcobalamin II deficiency Uncertain:1 Benign:1

Jan 29, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.61
CADD	Benign	8.5
DANN	Benign	0.71

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs138738105; hg19: chr22-31011755;