chr16-173540-C-G

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -1 ACMG points: 2P and 3B. PM1BP4_ModerateBS2_Supporting

The NM_000517.6(HBA2):c.369C>G(p.His123Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000121 in 1,607,450 control chromosomes in the GnomAD database, including 3 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Uncertain significance in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. H123L) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000074 ( 0 hom., cov: 25)

Exomes 𝑓: 0.00013 ( 3 hom. )

Consequence

HBA2
NM_000517.6 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1U:8O:1

Conservation

PhyloP100: -1.38

Publications

8 publications found

Variant links:

Genes affected

HBA2 (HGNC:4824): (hemoglobin subunit alpha 2) 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]

HBA2 Gene-Disease associations (from GenCC):

alpha thalassemia spectrum
Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), ClinGen
erythrocytosis, familial, 7
Inheritance: AD Classification: STRONG, LIMITED Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
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
Heinz body anemia
Inheritance: AD Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)
methemoglobinemia, alpha type
Inheritance: AD Classification: LIMITED Submitted by: ClinGen

HBA2 links:

ENSG00000294455 (HGNC:):

ENSG00000294455 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -1 ACMG points.

PM1

In a hotspot region, there are 9 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 3 benign, 9 uncertain in NM_000517.6

BP4

Computational evidence support a benign effect (MetaRNN=0.19518125).

BS2

High Homozygotes in GnomAdExome4 at 3 AD,AR geneVariant has number of homozygotes lower than other variant known as pathogenic in the gene, so the strength is limited to Supporting.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA2	NM_000517.6 link	c.369C>G	p.His123Gln	missense_variant	Exon 3 of 3	ENST00000251595.11	NP_000508.1	P69905D1MGQ2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HBA2	ENST00000251595.11 link	c.369C>G	p.His123Gln	missense_variant	Exon 3 of 3	1	NM_000517.6	ENSP00000251595.6		P69905

Frequencies

GnomAD3 genomes

AF:

0.0000740

AC:

AN:

148608

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00135

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000588

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.000157

AC:

AN:

248160

AF XY:

0.000134

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000580

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00169

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000533

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.000125

AC:

183

AN:

1458726

Hom.:

Cov.:

AF XY:

0.000106

AC XY:

AN XY:

725446

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

32018

American (AMR)

AF:

0.0000671

AC:

AN:

44682

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26090

East Asian (EAS)

AF:

0.000630

AC:

AN:

39682

South Asian (SAS)

AF:

0.00

AC:

AN:

85132

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53392

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5716

European-Non Finnish (NFE)

AF:

0.000138

AC:

153

AN:

1111766

Other (OTH)

AF:

0.0000332

AC:

AN:

60248

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.499

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Exome Hom

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

AF:

0.0000740

AC:

AN:

148724

Hom.:

Cov.:

AF XY:

0.0000964

AC XY:

AN XY:

72636

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

38424

American (AMR)

AF:

0.00

AC:

AN:

15174

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3460

East Asian (EAS)

AF:

0.00136

AC:

AN:

5156

South Asian (SAS)

AF:

0.00

AC:

AN:

4632

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10616

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.0000588

AC:

AN:

67970

Other (OTH)

AF:

0.00

AC:

AN:

2086

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.489

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome 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

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.0000491

ExAC

AF:

0.000157

AC:

Asia WGS

AF:

0.000939

AC:

AN:

3208

EpiCase

AF:

0.0000545

EpiControl

AF:

0.000297

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1Uncertain:8Other:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

alpha Thalassemia

Pathogenic:1Uncertain:2

Sep 16, 2020

Natera, Inc.

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Nov 29, 2022

Baylor Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Juno Genomics, Hangzhou Juno Genomics, Inc

Significance:Likely pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

PM3_VeryStrong+PP4 -

not provided

Uncertain:2

Nov 13, 2024

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The Hb Westmead variant (HBA2: c.369C>G; p.His123Gln, also known as His122Gln when numbered from the mature protein, rs41479347, HbVar ID: 185) has been reported in the heterozygous state in multiple individuals of East Asian descent, but has not been associated with significant clinical symptoms (Jiang 2020, Ma 2001, Viprakasit 2014, Wong 2004, HbVar database and references therein). This variant has been reported in homozygous individuals with mild anemia (Jiang 2020). However, it is an unstable hemoglobin variant, and its co-occurrence with beta thalassemia results in milder symptoms for the patient (Scheps 2020, Wong 2004, HbVar database and references therein). This variant is reported in ClinVar (Variation ID: 439771). It is found in the East Asian population with an overall allele frequency of 0.17% (33/19844 alleles) in the Genome Aggregation Database (v2.1.1). Computational analyses are uncertain whether this variant is neutral or deleterious (REVEL: 0.618). Given the lack of clinical and functional data, the significance of the p.His123Gln variant is uncertain at this time. References: HbVar database: https://globin.bx.psu.edu/hbvar/menu.html Jiang F et al. Hb Westmead (HBA2: c.369C>G): Hematological Characteristics in Heterozygotes with and without a0-Thalassemia. Hemoglobin. 2020 May;44(3):153-155. PMID: 32436451. Ma E et al. Interaction between (--SEA) alpha-thalassemia deletion and uncommon non-deletional alpha-globin gene mutations in Chinese patients. Haematologica. 2001; 86(5):539-40. PMID: 11410420. Scheps KG et al. Curating the gnomAD database: Report of novel variants in the globin-coding genes and bioinformatics analysis. Hum Mutat. 2020 Jan;41(1):81-102. PMID: 31553106. Viprakasit V et al. Clinical presentation and molecular identification of four uncommon alpha globin variants in Thailand. Acta Haematol. 2014;131(2):88-94. PMID: 24081251. Wong W et al. Thalassemia intermedia due to co-inheritance of beta0/beta(+)-thalassemia and (--SEA) alpha-thalassemia/Hb Westmead (alpha122(H5)His > Gln (alpha2)) in a Chinese family. Hemoglobin. 2004; 28(2):151-6. PMID: 15182058. -

Apr 16, 2020

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Heinz body anemia

Uncertain:1

Nov 29, 2022

Baylor Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

alpha Thalassemia;C0700299:Heinz body anemia;C3161174:Hemoglobin H disease;C4693823:Erythrocytosis, familial, 7

Uncertain:1

Apr 28, 2022

Fulgent Genetics, Fulgent Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Erythrocytosis, familial, 7

Uncertain:1

Nov 29, 2022

Baylor Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Hemoglobin H disease

Uncertain:1

Nov 29, 2022

Baylor Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

HEMOGLOBIN WESTMEAD

Other:1

May 10, 2018

OMIM

Significance:other

Review Status:no assertion criteria provided

Collection Method:literature only

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Uncertain

0.073

BayesDel_noAF

Pathogenic

0.31

CADD

Benign

8.0

(source)

DANN

Benign

0.97

DEOGEN2

Benign

0.14

.;T

Eigen

Benign

-1.0

Eigen_PC

Benign

-1.3

FATHMM_MKL

Benign

0.20

M_CAP

Pathogenic

0.53

MetaRNN

Benign

0.20

T;T

MetaSVM

Uncertain

0.47

PhyloP100

-1.4

PrimateAI

Uncertain

0.58

PROVEAN

Pathogenic

-5.7

D;D

REVEL

Uncertain

0.62

Sift

Pathogenic

0.0

D;D

Sift4G

Benign

0.18

T;T

Vest4

0.41

MutPred

0.88

Gain of ubiquitination at K128 (P = 0.1103);.;

MVP

1.0

MPC

2.4

ClinPred

0.29

GERP RS

-8.5

gMVP

0.85

Mutation Taster

=7/93

disease causing

(source)

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

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over