rs201408393

Positions:

• chr22-30614345-T-C

Variant summary

Our verdict is Benign. Variant got -7 ACMG points: 2P and 9B. PM2 BP4_Strong BP6 BS1

The NM_000355.4(TCN2):​c.428-4T>C variant causes a splice region, splice polypyrimidine tract, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000236 in 1,614,050 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.0012 (1 hom., cov: 32)
  • Exomes 𝑓: 0.00013 (0 hom.)
• Consequence: TCN2 NM_000355.4 splice_region, splice_polypyrimidine_tract, intron
• Scores: Splicing: ADA: 0.00004095
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:3
• Conservation: PhyloP100: 0.0350

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 -7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.92).
• BP6: Variant 22-30614345-T-C is Benign according to our data. Variant chr22-30614345-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 341194.We mark this variant Likely_benign, oryginal submissions are: {Benign=1, Likely_benign=2, Uncertain_significance=1}.
• BS1: Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.00122 (185/152226) while in subpopulation AFR AF= 0.00402 (167/41552). AF 95% confidence interval is 0.00352. There are 1 homozygotes in gnomad4. There are 89 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TCN2	NM_000355.4	c.428-4T>C		splice_region_variant, splice_polypyrimidine_tract_variant, intron_variant		ENST00000215838.8
TCN2	NM_001184726.2	c.347-4T>C		splice_region_variant, splice_polypyrimidine_tract_variant, intron_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TCN2	ENST00000215838.8	c.428-4T>C		splice_region_variant, splice_polypyrimidine_tract_variant, intron_variant		1	NM_000355.4	P2

Frequencies

GnomAD3 genomes AF: 0.00120 AC: 183 AN: 152108 Hom.: 1 Cov.: 32

Gnomad AFR AF: 0.00398

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000983

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: 0.00144

GnomAD3 exomes AF: 0.000275 AC: 69 AN: 251004 Hom.: 0 AF XY: 0.000206 AC XY: 28 AN XY: 135722

Gnomad AFR exome AF: 0.00382

Gnomad AMR exome AF: 0.000174

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.000163

GnomAD4 exome AF: 0.000134 AC: 196 AN: 1461824 Hom.: 0 Cov.: 32 AF XY: 0.000120 AC XY: 87 AN XY: 727204

Gnomad4 AFR exome AF: 0.00505

Gnomad4 AMR exome AF: 0.000201

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: 0.00000180

Gnomad4 OTH exome AF: 0.000265

GnomAD4 genome AF: 0.00122 AC: 185 AN: 152226 Hom.: 1 Cov.: 32 AF XY: 0.00120 AC XY: 89 AN XY: 74426

Gnomad4 AFR AF: 0.00402

Gnomad4 AMR AF: 0.000982

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: 0.00142

Alfa AF: 0.00112 Hom.: 0

Bravo AF: 0.00134

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Transcobalamin II deficiency Uncertain:1 Benign:2

Benign, criteria provided, single submitter	clinical testing	Invitae	Jan 30, 2024	- -
Likely benign, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Aug 10, 2023	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 13, 2018	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. -

TCN2-related disorder Benign:1

Likely benign, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Jul 14, 2019

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.92
CADD	Benign	0.36
DANN	Benign	0.50

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.000041
dbscSNV1_RF	Benign	0.0080
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

Other links and lift over

dbSNP: rs201408393; hg19: chr22-31010332;