16-172976-G-C

Variant names:

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 1P and 1B. PP3BP6

The NM_000517.6(HBA2):c.64G>C(p.Ala22Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. In-silico tool predicts a pathogenic 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 Likely benign in UniProt. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A22D) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.0 ( 0 hom., cov: 2)

Exomes 𝑓: 0.000022 ( 1 hom. )

Failed GnomAD Quality Control

Consequence

HBA2
NM_000517.6 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1B:1

Conservation

PhyloP100: 0.550

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 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 0 ACMG points.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.773

BP6

Variant 16-172976-G-C is Benign according to our data. Variant chr16-172976-G-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 801178.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=1, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA2	NM_000517.6 link	c.64G>C	p.Ala22Pro	missense_variant	Exon 1 of 3	ENST00000251595.11	NP_000508.1	P69905D1MGQ2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	UniProt
HBA2	ENST00000251595.11 link	c.64G>C	p.Ala22Pro	missense_variant	Exon 1 of 3	1	NM_000517.6	ENSP00000251595.6	P69905
HBA2	ENST00000484216.1 link	c.31G>C	p.Ala11Pro	missense_variant	Exon 1 of 2	1		ENSP00000495899.1	A0A2R8Y7C0
HBA2	ENST00000482565.1 link	n.83G>C		non_coding_transcript_exon_variant	Exon 1 of 2	1
HBA2	ENST00000397806.1 link	c.-2+18G>C		intron_variant	Intron 1 of 2	2		ENSP00000380908.1	G3V1N2

Frequencies

GnomAD3 genomes

AF:

0.00

AC:

AN:

4754

Hom.:

Cov.:

FAILED QC

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000188

AC:

AN:

53330

Hom.:

AF XY:

0.0000372

AC XY:

AN XY:

26890

show subpopulations

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 SAS exome

AF:

0.000167

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000219

AC:

AN:

411840

Hom.:

Cov.:

AF XY:

0.0000323

AC XY:

AN XY:

216496

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.000158

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000405

Gnomad4 OTH exome

AF:

0.0000425

GnomAD4 genome

Data not reliable, filtered out with message: AC0;AS_VQSR

AF:

0.00

AC:

AN:

4724

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

2328

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1Benign:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Uncertain:1Benign:1

Mar 23, 2022

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dec 09, 2024

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The HB2 c.64G>C (p.Ala22Pro), also known as Hb Fontainebleau, variant is reported as having normal stability (see HbVar, http://globin.bx.psu.edu/cgi-bin/hbvar/counter, PMID: 2599878 (2009)). This variant has been observed in a screening study of alpha thalassemia carriers (PMID: 29627922 (2018)). It has also been detected in an individual with suspected hemoglobinopathy (PMID: 38708170 (2024)). The variant has been reported in homozygous and compound heterozygous individuals with microcytosis (PMID: 22461654 (2012), 24826794 (2014), 26036869 (2015), and 30728682 (2019)) as well as in individuals with normal red cell indices (PMID: 19657841 (2009)). Based on the available information, we are unable to determine the clinical significance of this variant. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Uncertain

0.11

BayesDel_noAF

Pathogenic

0.19

CADD

Benign

DANN

Uncertain

0.98

Eigen

Benign

-0.70

Eigen_PC

Benign

-0.75

FATHMM_MKL

Benign

0.11

M_CAP

Pathogenic

0.62

MetaRNN

Pathogenic

0.77

MetaSVM

Uncertain

-0.098

PrimateAI

Uncertain

0.65

PROVEAN

Uncertain

-2.5

REVEL

Uncertain

0.57

Sift

Uncertain

0.014

Sift4G

Uncertain

0.056

Vest4

0.22

MutPred

0.83

Gain of methylation at K17 (P = 0.0559);

MVP

1.0

MPC

1.7

ClinPred

0.085

GERP RS

3.0

gMVP

0.95

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.060

Details are displayed if max score is > 0.2

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

Publications

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over