Genetic Variant HBA2:p.Ala121Val (chr16-173533-C-T) – ACMG Classification: Uncertain_significance (3 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 4P and 1B. PM1PM2BP4

The NM_000517.6(HBA2):c.362C>T(p.Ala121Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000686 in 1,458,534 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: not found (cov: 25)

Exomes 𝑓: 6.9e-7 ( 0 hom. )

Consequence

HBA2
NM_000517.6 missense

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 0.0830

Publications

0 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: Uncertain_significance. The variant received 3 ACMG points.

PM1

In a hotspot region, there are 7 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 4 benign, 14 uncertain in NM_000517.6

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.39110097).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA2	NM_000517.6 link	c.362C>T	p.Ala121Val	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.362C>T	p.Ala121Val	missense_variant	Exon 3 of 3	1	NM_000517.6	ENSP00000251595.6		P69905

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

6.86e-7

AC:

AN:

1458534

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

725366

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

31950

American (AMR)

AF:

0.00

AC:

AN:

44670

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26086

East Asian (EAS)

AF:

0.00

AC:

AN:

39678

South Asian (SAS)

AF:

0.00

AC:

AN:

85120

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53364

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5716

European-Non Finnish (NFE)

AF:

9.00e-7

AC:

AN:

1111714

Other (OTH)

AF:

0.00

AC:

AN:

60236

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.525

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.12

BayesDel_addAF

Pathogenic

0.20

BayesDel_noAF

Uncertain

0.050

CADD

Benign

(source)

DANN

Uncertain

0.99

DEOGEN2

Benign

0.037

.;T

Eigen

Benign

-0.68

Eigen_PC

Benign

-0.71

FATHMM_MKL

Benign

0.25

M_CAP

Pathogenic

0.35

MetaRNN

Benign

0.39

T;T

MetaSVM

Uncertain

0.15

PhyloP100

0.083

PrimateAI

Benign

0.36

PROVEAN

Benign

-1.8

N;N

REVEL

Uncertain

0.58

Sift

Uncertain

0.0010

D;D

Sift4G

Benign

0.094

T;T

Vest4

0.27

MutPred

0.47

Loss of disorder (P = 0.1461);.;

MVP

1.0

MPC

1.3

ClinPred

0.79

GERP RS

1.9

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.3

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

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Computational scores

Splicing

Publications

Other links and lift over