rs34527846

Positions:

• chr11-5226802-A-C
• chr11-5226802-A-G
• chr11-5226802-A-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 10P and 1B. PM2 PP5_Very_Strong BP4

The NM_000518.5(HBB):​c.93-3T>G variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,461,274 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 2/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: HBB NM_000518.5 splice_region, intron
• Scores: Splicing: ADA: 0.9007
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:7
• Conservation: PhyloP100: -0.194

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]

HBB (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 11-5226802-A-C is Pathogenic according to our data. Variant chr11-5226802-A-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 36341.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr11-5226802-A-C is described in Lovd as [Pathogenic].
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.8). . Strength limited to SUPPORTING due to the PP5.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HBB	NM_000518.5	c.93-3T>G		splice_region_variant, intron_variant		ENST00000335295.4	NP_000509.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HBB	ENST00000335295.4	c.93-3T>G		splice_region_variant, intron_variant		1	NM_000518.5	ENSP00000333994.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000159 AC: 4 AN: 251100 Hom.: 0 AF XY: 0.00000737 AC XY: 1 AN XY: 135674

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 SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000353

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461274 Hom.: 0 Cov.: 36 AF XY: 0.00000413 AC XY: 3 AN XY: 726974

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000232

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000434 Hom.: 0

ClinVar

Significance: Pathogenic/Likely 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, no assertion criteria provided	clinical testing	Genetic Laboratory, Salmaniya Medical Complex	-	- -
Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Mar 25, 2021	- -

not provided Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Aug 20, 2021	The variant found in at least one symptomatic individual. The variant is predicted to negatively affect a known splice site. The variant occurs in multiple cases with a lone recessive pathogenic/likely pathogenic variant in the same gene, and several have a phenotype known to be consistent with disease. -
Likely pathogenic, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Jan 24, 2023	The HBB: c.93-3T>G variant (also known as IVS-I-128 (T->G), rs34527846, HbVar ID: 829) is reported in the compound heterozygous state in individuals with beta (+) thalassemia (Chiou 1993, Hussain 2017, Wong 1989, see link to HbVar and references therein). This variant is also reported in ClinVar (Variation ID: 36341), and is only observed on four alleles in the Genome Aggregation Database, indicating it is not a common polymorphism. This is an intronic variant in a weakly conserved nucleotide, but computational analyses (Alamut v.2.11) predict that this variant may impact splicing by weakening the nearby canonical acceptor splice site. Based on available information, this variant is considered to be likely pathogenic. References: Link to HbVar database: https://globin.bx.psu.edu/hbvar/menu.html Chiou SS et al. Molecular basis and haematological characterization of beta-thalassaemia major in Taiwan, with a mutation of IVS-1 3' end TAG-->GAG in a Chinese patient. Br J Haematol. 1993 Jan;83(1):112-7. PMID: 8435318. Hussain A et al. Rare beta-Globin Gene Mutations in Pakistan. Hemoglobin. 2017 Mar;41(2):100-103. PMID: 28670940. Wong C et al. Beta-thalassemia due to two novel nucleotide substitutions in consensus acceptor splice sequences of the beta-globin gene. Blood. 1989 Mar;73(4):914-8. PMID: 2920213. -

Beta thalassemia intermedia Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

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

Mar 02, 2022

Variant summary: HBB c.93-3T>G alters a non-conserved nucleotide located close to a canonical splice site and therefore could affect mRNA splicing, leading to a significantly altered protein sequence. Several computational tools predict a significant impact on normal splicing: Two predict the variant abolishes the canonical 5' splicing donor site. Three predict the variant weakens the canonical 5' splicing donor site. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 2e-05 in 252420 control chromosomes. c.93-3T>G has been reported in the literature in multiple individuals affected with Beta Thalassemia Intermedia (example, Wong_1989, Chiou_1993, Ho_1998, Sinha_2009, Al-Allawi_2014, Hassan_2015, Hussain_2017). These data indicate that the variant is very likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The The ITHANET community portal has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation and classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Beta-plus-thalassemia Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Mar 01, 1989

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.80
CADD	Benign	12
DANN	Benign	0.84

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.90
dbscSNV1_RF	Benign	0.66
SpliceAI score (max)		0.38		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.38		Position offset: -3

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

Publications

LitVar

Other links and lift over

dbSNP: rs34527846; hg19: chr11-5248032;