rs34090856

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 0P and 2B. BP4_Moderate

The NM_000558.5(HBA1):c.17C>A(p.Ala6Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A6P) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.0 ( 0 hom., cov: 28)

Exomes 𝑓: 0.0000097 ( 0 hom. )

Failed GnomAD Quality Control

Consequence

HBA1
NM_000558.5 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:3O:1

Conservation

PhyloP100: -0.565

Publications

4 publications found

Variant links:

Genes affected

HBA1 (HGNC:4823): (hemoglobin subunit alpha 1) The human alpha globin gene cluster located on chromosome 16 spans about 30 kb and includes seven loci: 5'- zeta - pseudozeta - mu - pseudoalpha-1 - alpha-2 - alpha-1 - theta - 3'. The alpha-2 (HBA2) and alpha-1 (HBA1) coding sequences are identical. These genes differ slightly over the 5' untranslated regions and the introns, but they differ significantly over the 3' untranslated regions. Two alpha chains plus two beta chains constitute HbA, which in normal adult life comprises about 97% of the total hemoglobin; alpha chains combine with delta chains to constitute HbA-2, which with HbF (fetal hemoglobin) makes up the remaining 3% of adult hemoglobin. Alpha thalassemias result from deletions of each of the alpha genes as well as deletions of both HBA2 and HBA1; some nondeletion alpha thalassemias have also been reported. [provided by RefSeq, Jul 2008]

HBA1 Gene-Disease associations (from GenCC):

alpha thalassemia spectrum
Inheritance: AR, SD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics
erythrocytosis, familial, 7
Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
hemoglobin M disease
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
Hb Bart's hydrops fetalis
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
hemoglobin H disease
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
methemoglobinemia, alpha type
Inheritance: AD Classification: LIMITED Submitted by: ClinGen
Heinz body anemia
Inheritance: AR Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)

HBA1 links:

ENSG00000294436 (HGNC:):

ENSG00000294436 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -2 ACMG points.

BP4

Computational evidence support a benign effect (MetaRNN=0.19086808).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000558.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	HBA1	NM_000558.5	MANE Select	c.17C>A	p.Ala6Asp	missense	Exon 1 of 3	NP_000549.1

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
HBA1	ENST00000320868.9	TSL:1 MANE Select	c.17C>A	p.Ala6Asp	missense	Exon 1 of 3	ENSP00000322421.5
HBA1	ENST00000472694.1	TSL:1	n.36C>A		non_coding_transcript_exon	Exon 1 of 2
ENSG00000294436	ENST00000723616.1		n.219G>T		non_coding_transcript_exon	Exon 2 of 2

Frequencies

GnomAD3 genomes

AF:

0.00

AC:

AN:

152136

Hom.:

Cov.:

Gnomad AFR

AF:

0.00

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

Data not reliable, filtered out with message: AS_VQSR

AF:

0.00000973

AC:

AN:

1438688

Hom.:

Cov.:

AF XY:

0.0000112

AC XY:

AN XY:

714426

show subpopulations

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

32438

American (AMR)

AF:

0.00

AC:

AN:

41946

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25770

East Asian (EAS)

AF:

0.00

AC:

AN:

38650

South Asian (SAS)

AF:

0.00

AC:

AN:

83286

European-Finnish (FIN)

AF:

0.00

AC:

AN:

51676

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5272

European-Non Finnish (NFE)

AF:

0.0000127

AC:

AN:

1100142

Other (OTH)

AF:

0.00

AC:

AN:

59508

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.300

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

Data not reliable, filtered out with message: AC0

AF:

0.00

AC:

AN:

152136

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74316

African (AFR)

AF:

0.00

AC:

AN:

41434

American (AMR)

AF:

0.00

AC:

AN:

15288

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3462

East Asian (EAS)

AF:

0.00

AC:

AN:

5204

South Asian (SAS)

AF:

0.00

AC:

AN:

4832

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10624

Middle Eastern (MID)

AF:

0.00

AC:

AN:

314

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

67976

Other (OTH)

AF:

0.00

AC:

AN:

2090

Alfa

AF:

0.00

Hom.:

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3Other:1

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Uncertain:2

May 27, 2023

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

In the published literature, this variant has been reported in individuals with normal hematological characterizations (PMID: 5870555 (1965), 5169069 (1971)), as well as individuals with diabetes (PMID: 25109349 (2014)), and individuals with hypochromic microcytic anemia (PMID: 23402770 (2013)). This variant is reported as having normal stability and normal cell morphology (PMID: 5870555 (1965), 5169069 (1971)). This variant has not been reported in large, multi-ethnic general populations (Genome Aggregation Database, http://gnomad.broadinstitute.org). Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded predictions that this variant is benign. Based on the available information, we are unable to determine the clinical significance of this variant.

May 11, 2024

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The Hb J Toronto variant (HBA1 c.17C>A; p.Ala6Asp, also known as or Ala5Asp when numbered from the mature protein, rs34090856, HbVarID: 3) is reported in the literature in the heterozygous state and in the compound heterozygous state with the 3.7kb deletion in individuals without any significant hematological symptoms (see HbVar and references therein, Mahdavi 2012, Van Laer 2014). Aberrant HbA1c measurements have been reported in several individuals with this variant (Van Laer 2014). This variant is reported in ClinVar (Variation ID: 15765), and is absent from the Genome Aggregation Database, indicating it is not a common polymorphism. Computational analyses are uncertain whether this variant is neutral or deleterious (REVEL: 0.544). Due to limited information, the clinical significance of this variant is uncertain at this time. References: Link to HbVar database: https://globin.bx.psu.edu/hbvar/menu.html Mahdavi M et al. Report of haemoglobin J-Toronto and alpha thalassemia in a family from North of Iran. J Pak Med Assoc. 2012 Apr;62(4):396-8. PMID: 22755290. Van Laer C et al. Aberrant glycated haemoglobin (HbA1c) results leading to haemoglobinopathy diagnosis in four Belgian patients. Acta Clin Belg. 2014 Dec;69(6):456-9. PMID: 25109349.

alpha Thalassemia

Uncertain:1

Aug 31, 2021

Natera, Inc.

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

HEMOGLOBIN J (TORONTO)

Other:1

Jul 20, 2016

OMIM

Significance:other

Review Status:no assertion criteria provided

Collection Method:literature only

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.16

BayesDel_addAF

Uncertain

0.16

BayesDel_noAF

Uncertain

-0.010

CADD

Benign

7.5

(source)

DANN

Benign

0.73

DEOGEN2

Benign

0.14

Eigen

Benign

-0.78

Eigen_PC

Benign

-0.92

FATHMM_MKL

Benign

0.10

LIST_S2

Benign

0.81

M_CAP

Uncertain

0.13

MetaRNN

Benign

0.19

MetaSVM

Uncertain

-0.18

PhyloP100

-0.56

PrimateAI

Uncertain

0.55

PROVEAN

Benign

-1.2

REVEL

Uncertain

0.54

Sift

Benign

0.46

Sift4G

Benign

0.62

Vest4

0.26

MutPred

0.11

Loss of MoRF binding (P = 0.0116)

MVP

0.97

ClinPred

0.031

GERP RS

1.2

PromoterAI

-0.095

Neutral

(source)

Varity_R

0.19

gMVP

0.69

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.0

Details are displayed if max score is > 0.2

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over