rs63750953

Variant names:

• chr11-5227096-CTT-C
• rs63750953
• ENST00000647020.1:c.-77_-76delAA

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 3P and 0B. PM2 PP5

The ENST00000647020.1(HBB):​c.-77_-76delAA variant causes a 5 prime UTR change. The variant allele was found at a frequency of 0.00000657 in 152,166 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
• Consequence: HBB ENST00000647020.1 5_prime_UTR
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 4.41
• Publications: 9 publications found

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 Gene-Disease associations (from GenCC):

• dominant beta-thalassemia

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), ClinGen
• hemoglobin M disease

  Inheritance: AD Classification: DEFINITIVE, MODERATE, SUPPORTIVE Submitted by: Orphanet, Ambry Genetics, ClinGen
• beta thalassemia

  Inheritance: AR Classification: DEFINITIVE Submitted by: Myriad Women’s Health
• beta-thalassemia HBB/LCRB

  Inheritance: AR, SD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), ClinGen, Ambry Genetics
• sickle cell disease and related diseases

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• erythrocytosis, familial, 6

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp
• Heinz body anemia

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• sickle cell disease

  Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae)
• hereditary persistence of fetal hemoglobin-beta-thalassemia syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• beta-thalassemia intermedia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• beta-thalassemia major

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• delta-beta-thalassemia

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hemoglobin C disease

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hemoglobin C-beta-thalassemia syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hemoglobin E disease

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hemoglobin E-beta-thalassemia syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hereditary persistence of fetal hemoglobin-sickle cell disease syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• sickle cell-beta-thalassemia disease syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• sickle cell-hemoglobin c disease syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• sickle cell-hemoglobin d disease syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• sickle cell-hemoglobin E disease syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ENSG00000298932 (HGNC:):

ACMG classification

Our verdict: Uncertain_significance. The variant received 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 11-5227096-CTT-C is Pathogenic according to our data. Variant chr11-5227096-CTT-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 496005.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBB	NM_000518.5	c.-77_-76delAA		upstream_gene_variant		ENST00000335295.4	NP_000509.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HBB	ENST00000335295.4	c.-77_-76delAA		upstream_gene_variant		1	NM_000518.5	ENSP00000333994.3

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152166 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

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: 0.00

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152166 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74326

African (AFR) AF: 0.0000241 AC: 1 AN: 41436

American (AMR) AF: 0.00 AC: 0 AN: 15286

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5176

South Asian (SAS) AF: 0.00 AC: 0 AN: 4826

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10616

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68040

Other (OTH) AF: 0.00 AC: 0 AN: 2090

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000756

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Beta thalassemia intermedia Pathogenic:1

Apr 16, 2021

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

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: HBB c.-77_-76delAA is located in the untranscribed region upstream of the HBB gene region. The variant was absent in 249250 control chromosomes (gnomAD). c.-77_-76delAA has been reported in the literature in a neonate who showed FSA (Hb S/beta+ -thalassemia) profile on NBS (Eng_2007) and also in another 8-yr-old patient with mild BTHAL ITMD who was compound heterozygous for this variant and other ITMD-causing mutation c.-138C>T (Basran_2008). In the latter patient, two unaffected family members with BTHAL trait were carrier for the variant. These data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Eng et al report that this alteration not only changes the sequence of the ATAA box from ATAAAA to ATAAGT, but also alters the distance between the ATAA box and the normal transcription start sequence. Both the sequence of the ATAA box and the spacing relative to the transcription start site are thought to be important determinants of tissue-specific expression of mammalian genes (Eng_2007). No other ClinVar submitters have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Hb SS disease;C0019025:Hereditary persistence of fetal hemoglobin;C0700299:Heinz body anemia;C1840779:METHEMOGLOBINEMIA, BETA TYPE;C1858990:Dominant beta-thalassemia;C1970028:Malaria, susceptibility to;C4693822:Erythrocytosis, familial, 6;CN322236:Beta-thalassemia HBB/LCRB Pathogenic:1

Jun 20, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Uncertain:1

Mar 22, 2024

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The HBB c.-77_-76del variant (also known as -27(-AA), -25AA deletion, and rs63750953) occurs in the TATA box of the gene promoter and may affect beta globin (HBB) expression. This variant has been reported in the published literature in an individual affected with beta thalassemia intermedia who also carried another deleterious beta globin variant (PMID: 16732578 (2008)). Heterozygotes in this family had a normal Hb level, borderline microcytosis, and elevated Hb A2. One functional study showed that this TATA box deletion variant significantly reduces the binding of the TATA box binding protein and slows the formation of the TBP/TATA complex (Sharypova et al. Vavilov Journal of Genetics and Breeding 2018 22(1):145). The frequency of this variant in the general population, 0.0000066 (1/152166 chromosomes (Genome Aggregation Database, http://gnomad.broadinstitute.org)), is uninformative in the assessment of its pathogenicity. Based on the available information, we are unable to determine the clinical significance of this variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		4.4
Mutation Taster		=32/68	disease causing (ClinVar)

Splicing

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

Other links and lift over

dbSNP: rs63750953; hg19: chr11-5248326;