Genetic Variant HBA1:p.Ala13Val (chr16-176754-C-T) – ACMG Classification: Uncertain_significance (2 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The NM_000558.5(HBA1):c.38C>T(p.Ala13Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A13D) has been classified as Uncertain significance.

Frequency

Genomes: not found (cov: 28)

Exomes 𝑓: 7.0e-7 ( 0 hom. )

Failed GnomAD Quality Control

Consequence

HBA1
NM_000558.5 missense

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -0.107

Publications

10 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:

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ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA1	NM_000558.5 link	c.38C>T	p.Ala13Val	missense_variant	Exon 1 of 3	ENST00000320868.9	NP_000549.1	P69905D1MGQ2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HBA1	ENST00000320868.9 link	c.38C>T	p.Ala13Val	missense_variant	Exon 1 of 3	1	NM_000558.5	ENSP00000322421.5		P69905

Frequencies

GnomAD3 genomes

Cov.:

GnomAD2 exomes

AF:

0.00

AC:

AN:

164998

AF XY:

0.00

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

Data not reliable, filtered out with message: AS_VQSR

AF:

6.97e-7

AC:

AN:

1435146

Hom.:

Cov.:

AF XY:

0.00000140

AC XY:

AN XY:

712442

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:

32378

American (AMR)

AF:

0.00

AC:

AN:

41574

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25732

East Asian (EAS)

AF:

0.00

AC:

AN:

38568

South Asian (SAS)

AF:

0.00

AC:

AN:

82760

European-Finnish (FIN)

AF:

0.00

AC:

AN:

51332

Middle Eastern (MID)

AF:

0.00

AC:

AN:

4846

European-Non Finnish (NFE)

AF:

9.10e-7

AC:

AN:

1098638

Other (OTH)

AF:

0.00

AC:

AN:

59318

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.225

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

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.11

BayesDel_addAF

Uncertain

0.14

BayesDel_noAF

Uncertain

-0.030

CADD

Benign

(source)

DANN

Uncertain

0.99

DEOGEN2

Benign

0.34

Eigen

Benign

-0.60

Eigen_PC

Benign

-0.78

FATHMM_MKL

Benign

0.40

LIST_S2

Benign

0.85

M_CAP

Pathogenic

0.38

MetaRNN

Uncertain

0.45

MetaSVM

Uncertain

0.20

PhyloP100

-0.11

PrimateAI

Uncertain

0.52

PROVEAN

Uncertain

-2.4

REVEL

Uncertain

0.63

Sift

Uncertain

0.0010

Sift4G

Benign

0.061

Vest4

0.20

MutPred

0.68

Gain of methylation at K12 (P = 0.0365);

MVP

1.0

ClinPred

0.68

GERP RS

-0.29

PromoterAI

-0.074

Neutral

(source)

Varity_R

0.41

gMVP

0.61

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

ClinVar

Computational scores

Splicing

Publications

Other links and lift over