20-18525021-G-T

Variant names:

• chr20-18525021-G-T
• rs398124226
• NM_006363.6:c.689+1G>T

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1 PM2 PP5_Moderate

The NM_006363.6(SEC23B):​c.689+1G>T variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: SEC23B NM_006363.6 splice_donor, intron
• Scores: Splicing: ADA: 0.9999
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 9.17
• Publications: 0 publications found

Genes affected

SEC23B (HGNC:10702): (SEC23 homolog B, COPII coat complex component) The protein encoded by this gene is a member of the SEC23 subfamily of the SEC23/SEC24 family, which is involved in vesicle trafficking. The encoded protein has similarity to yeast Sec23p component of COPII. COPII is the coat protein complex responsible for vesicle budding from the ER. The function of this gene product has been implicated in cargo selection and concentration. Multiple alternatively spliced transcript variants have been identified in this gene. [provided by RefSeq, Feb 2010]

SEC23B Gene-Disease associations (from GenCC):

• congenital dyserythropoietic anemia type 2

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Orphanet, Laboratory for Molecular Medicine, G2P
• Cowden disease

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Cowden syndrome 7

  Inheritance: AD Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)
• congenital dyserythropoietic anemia

  Inheritance: AR Classification: LIMITED Submitted by: Genomics England PanelApp

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 20-18525021-G-T is Pathogenic according to our data. Variant chr20-18525021-G-T is described in ClinVar as Pathogenic. ClinVar VariationId is 2939603.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SEC23B	NM_006363.6	c.689+1G>T		splice_donor_variant, intron_variant	Intron 6 of 19	ENST00000650089.1	NP_006354.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SEC23B	ENST00000650089.1	c.689+1G>T		splice_donor_variant, intron_variant	Intron 6 of 19		NM_006363.6	ENSP00000497473.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 35

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Congenital dyserythropoietic anemia, type II;C4225179:Cowden syndrome 7 Pathogenic:1

Jan 23, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects a donor splice site in intron 6 of the SEC23B gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in SEC23B are known to be pathogenic (PMID: 19561605, 25044164). This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individual(s) with congenital dyserythropoietic anemia type II (PMID: 19561605, 19621418). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 2939603). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic.

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Uncertain	0.12
CADD	Pathogenic	32
DANN	Uncertain	0.99
DEOGEN2	Benign	0.0	.;.;.;.;.;.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.94
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Benign	0.0	.;.;.;.;.;.;.
MetaRNN	Benign	0.0	.;.;.;.;.;.;.
MutationAssessor	Benign	0.0	.;.;.;.;.;.;.
PhyloP100		9.2
PROVEAN	Benign	0.0	.;.;.;.;.;.;.
REVEL	Benign	0.0
Sift	Pathogenic	0.0	.;.;.;.;.;.;.
Sift4G	Pathogenic	0.0	.;.;.;.;.;.;.
Vest4		0.0
GERP RS		5.7
Mutation Taster		=0/100	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_DL_spliceai		1.0		Position offset: -1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs398124226; hg19: chr20-18505665;