ENST00000647020.1:c.-75G>C

Variant names:

• chr11-5227096-C-G
• rs63750400
• ENST00000647020.1:c.-75G>C

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 3P and 1B. PM2 PP5 BP4

The ENST00000647020.1(HBB):​c.-75G>C variant causes a 5 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000155 in 1,030,100 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.000039 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000011 (0 hom.)
• Consequence: HBB ENST00000647020.1 5_prime_UTR
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:4
• Conservation: PhyloP100: -0.0370

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 Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 11-5227096-C-G is Pathogenic according to our data. Variant chr11-5227096-C-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 36294.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=2}. Variant chr11-5227096-C-G is described in Lovd as [Pathogenic].
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.5). . Strength limited to SUPPORTING due to the PP5.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBB	NM_000518.5	c.-75G>C		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.-75G>C		upstream_gene_variant		1	NM_000518.5	ENSP00000333994.3

Frequencies

GnomAD3 genomes AF: 0.0000394 AC: 6 AN: 152166 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000145

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

GnomAD4 exome AF: 0.0000114 AC: 10 AN: 877934 Hom.: 0 Cov.: 12 AF XY: 0.0000196 AC XY: 9 AN XY: 459750

Gnomad4 AFR exome AF: 0.000226

Gnomad4 AMR exome AF: 0.0000235

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.0000194

Gnomad4 NFE exome AF: 0.00000515

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000394 AC: 6 AN: 152166 Hom.: 0 Cov.: 32 AF XY: 0.0000404 AC XY: 3 AN XY: 74326

Gnomad4 AFR AF: 0.000145

Gnomad4 AMR AF: 0.00

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: 0.00

Bravo AF: 0.0000604

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

beta Thalassemia Pathogenic:1 Uncertain:1

Dec 28, 2017

Counsyl

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Nov 25, 2019

The ITHANET community portal, The Cyprus Institute of Neurology and Genetics

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: curation

- -

not provided Pathogenic:1

May 15, 2017

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not specified Uncertain:1

Feb 07, 2024

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

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: The variant, HBB c.-75G>C is located 25 nucleotides upstream of the HBB gene in the untranscribed promoter region, near the conserved TATA box (nucleotide positions -32 to -26 from transcription initiation site), which is known to be involved in transcriptional regulation. The variant allele was found at a frequency of 1.6e-05 in 1030100 control chromosomes (gnomAD v4.0.0). This frequency is not significantly higher than estimated for a pathogenic variant in HBB causing Beta Thalassemia (1.6e-05 vs 0.011), allowing no conclusion about variant significance. At least one publication reports experimental evidence evaluating an impact on protein function. These results showed no damaging effect of this variant (Kircher_2019). The following publications have been ascertained in the context of this evaluation (PMID: 17486493, 21250885, 31395865). ClinVar contains an entry for this variant (Variation ID: 36294). Based on the evidence outlined above, the variant was classified as uncertain significance. -

HBB-related disorder Uncertain:1

Nov 21, 2023

PreventionGenetics, part of Exact Sciences

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

The HBB c.-75G>C variant is located in the 5' untranslated region. This variant was reported in an individual with newborn screening results consistent with Hb S/beta+ thalassemia; that patient was also found to carry an Hb S allele (Patient #1 in Eng et al. 2007. PubMed ID: 17486493). In a study of promoter function, the c.-75G>C variant was reported to exhibit similar promoter activity to wild-type (Supplementary Table 10 in Kircher et al. 2019. PubMed ID: 31395865). Other variants at this location (c.-75G>A, c.-75G>T) and numerous other variants nearby have been reported in patients with beta-thalassemia (Human Gene Mutation Database, http://www.hgmd.cf.ac.uk/ac/index.php). This variant is reported in 0.011% of alleles in individuals of African descent in gnomAD (http://gnomad.broadinstitute.org/variant/11-5248326-C-G). In ClinVar, it is reported with conflicting interpretations including uncertain, likely pathogenic and pathogenic (https://www.ncbi.nlm.nih.gov/clinvar/variation/36294/). At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

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 Uncertain:1

Apr 11, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.50
CADD	Benign	12
DANN	Benign	0.88

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs63750400; hg19: chr11-5248326;