rs63751457

Variant names:

• chr16-172981-C-A
• rs63751457
• NM_000517.6:c.69C>A

Your query was ambiguous. Multiple possible variants found:

• chr16-172981-C-A
• chr16-172981-C-T

Variant summary

Our verdict is Likely benign. The variant received -5 ACMG points: 0P and 5B. BP4_Strong BP7

The NM_000517.6(HBA2):​c.69C>A​(p.Gly23Gly) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. G23G) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 2)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: HBA2 NM_000517.6 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -3.95
• 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: Likely_benign. The variant received -5 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.78).
• BP7: Synonymous conserved (PhyloP=-3.95 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA2	NM_000517.6	c.69C>A	p.Gly23Gly	synonymous_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.69C>A	p.Gly23Gly	synonymous_variant	Exon 1 of 3	1	NM_000517.6	ENSP00000251595.6

Frequencies

GnomAD3 genomes Cov.: 2

GnomAD4 exome AF: 0.00000477 AC: 2 AN: 419174 Hom.: 0 Cov.: 0 AF XY: 0.00000907 AC XY: 2 AN XY: 220470

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

African (AFR) AF: 0.00 AC: 0 AN: 10232

American (AMR) AF: 0.00 AC: 0 AN: 18100

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 12920

East Asian (EAS) AF: 0.0000349 AC: 1 AN: 28664

South Asian (SAS) AF: 0.00 AC: 0 AN: 44530

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 27340

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 1802

European-Non Finnish (NFE) AF: 0.00000398 AC: 1 AN: 251560

Other (OTH) AF: 0.00 AC: 0 AN: 24026

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000203476), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 2

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.78
CADD	Benign	3.0
DANN	Benign	0.72
PhyloP100		-3.9
PromoterAI		-0.032	Neutral
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs63751457; hg19: chr16-222980;