rs33950507

Positions:

• chr11-5226943-C-A
• chr11-5226943-C-G
• chr11-5226943-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000518.5(HBB):​c.79G>T​(p.Glu27Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: HBB NM_000518.5 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:7
• Conservation: PhyloP100: 1.15

Genes affected

HBB (HGNC:4827): (hemoglobin subunit beta) The alpha (HBA) and beta (HBB) loci determine the structure of the 2 types of polypeptide chains in adult hemoglobin, Hb A. The normal adult hemoglobin tetramer consists of two alpha chains and two beta chains. Mutant beta globin causes sickle cell anemia. Absence of beta chain causes beta-zero-thalassemia. Reduced amounts of detectable beta globin causes beta-plus-thalassemia. The order of the genes in the beta-globin cluster is 5'-epsilon -- gamma-G -- gamma-A -- delta -- beta--3'. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 141 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 11-5226943-C-A is Pathogenic according to our data. Variant chr11-5226943-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 38650.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr11-5226943-C-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HBB	NM_000518.5	c.79G>T	p.Glu27Ter	stop_gained	1/3	ENST00000335295.4	NP_000509.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HBB	ENST00000335295.4	c.79G>T	p.Glu27Ter	stop_gained	1/3	1	NM_000518.5	ENSP00000333994	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

beta Thalassemia Pathogenic:3

Pathogenic, no assertion criteria provided	curation	The ITHANET community portal, The Cyprus Institute of Neurology and Genetics	Nov 25, 2019	- -
Pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Jun 04, 2018	- -
Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Aug 17, 2017	- -

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Aug 21, 2023	The Codon 26 (G>T) variant (HBB: c.79G>T; p.Glu27Ter, also known as Glu26Ter when numbered from the mature protein, rs33950507, HbVar ID: 808) is reported in an individual with beta thalassemia that also harbored the HbE variant (HbVar database and references therein). In testing performed at ARUP Laboratories, this variant has also been observed in trans to a frameshift variant in an individual with severe anemia. The p.Glu27Ter variant is absent from the Genome Aggregation Database, indicating it is not a common polymorphism. This variant induces an early termination codon and is predicted to result in a truncated protein or mRNA subject to nonsense-mediated decay. Consistent with predictions, functional studies demonstrate an absence of beta globin protein and mRNA in cells expressing this variant (Neu-Yilik 2011). Based on available information, this variant is considered to be pathogenic. References: HbVar database link: https://globin.bx.psu.edu/hbvar/menu.html Neu-Yilik G et al. Mechanism of escape from nonsense-mediated mRNA decay of human beta-globin transcripts with nonsense mutations in the first exon. RNA. 2011 May;17(5):843-54. PMID: 21389146. -
Pathogenic, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Jun 30, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Apr 17, 2021	For these reasons, this variant has been classified as Pathogenic. This variant has been observed in individual(s) with beta thalassemia (PMID: 1974422). It is known as codon 26 GAG>TAG. ClinVar contains an entry for this variant (Variation ID: 38650). This variant is not present in population databases (ExAC no frequency). This sequence change creates a premature translational stop signal (p.Glu27*) in the HBB gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in HBB are known to be pathogenic (PMID: 23637309). -

Hemoglobinopathy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Dec 14, 2017

Variant summary: The HBB c.79G>T (p.Glu27X, also known as CD26 G>T) variant results in a premature termination codon, predicted to cause a truncated or absent HBB protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory (e.g. c.85dupC/p.Leu29fsX16, c.110delC/p.Pro37fsX25, etc.). One in silico tool predicts a damaging outcome for this variant. This variant is absent in 277088 control chromosomes. It has been reported in multiple affected individuals. Variant involving the same neucleotide c.79G>A/p.Glu27Lys is a common HbE variant and the region around codon 26 has been suggested as mutation hotspot(Fucharoen_1990). In addition, multiple clinical diagnostic laboratories/reputable databases classified this variant as pathogenic. Taken together, this variant is classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.60	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	44
DANN	Uncertain	1.0
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.67
FATHMM_MKL	Uncertain	0.89	D
MutationTaster	Benign	1.0	A
Vest4		0.40
GERP RS		4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.19		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: rs33950507; hg19: chr11-5248173;