NM_000517.6:c.71A>C

Variant names:

• chr16-172983-A-C
• rs281864820
• NM_000517.6:c.71A>C

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM1

The NM_000517.6(HBA2):​c.71A>C​(p.Glu24Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. Variant has been reported in ClinVar as Uncertain significance (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. E24K) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 2)
• Consequence: HBA2 NM_000517.6 missense
• Clinical Significance: Uncertain significance no assertion criteria provided U:1
• Conservation: PhyloP100: 0.525
• Publications: 0 publications found

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

ENSG00000294455 (HGNC:):

ACMG classification

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

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 5 benign, 13 uncertain in NM_000517.6

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA2	NM_000517.6	c.71A>C	p.Glu24Ala	missense_variant	Exon 1 of 3	ENST00000251595.11	NP_000508.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HBA2	ENST00000251595.11	c.71A>C	p.Glu24Ala	missense_variant	Exon 1 of 3	1	NM_000517.6	ENSP00000251595.6

Frequencies

GnomAD3 genomes Cov.: 2

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: no assertion criteria provided

Submissions by phenotype

alpha Thalassemia Uncertain:1

Jan 27, 2025

Natera, Inc.

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.078
BayesDel_addAF	Uncertain	0.12	D
BayesDel_noAF	Uncertain	-0.070
CADD	Benign	9.6
DANN	Benign	0.91
Eigen	Benign	-1.1
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.13	N
M_CAP	Pathogenic	0.44	D
MetaRNN	Uncertain	0.70	D
MetaSVM	Benign	-0.45	T
PhyloP100		0.53
PrimateAI	Uncertain	0.62	T
PROVEAN	Benign	-1.7	N
REVEL	Uncertain	0.51
Sift	Benign	0.10	T
Sift4G	Benign	0.72	T
Vest4		0.35
MutPred		0.85		Loss of disorder (P = 0.0581);
MVP		1.0
MPC		1.4
ClinPred		0.064	T
GERP RS		1.4
PromoterAI		0.027	Neutral
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
gMVP		0.76

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.080		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs281864820; hg19: chr16-222982;