16-173259-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 1P and 0B. PP3

The NM_000517.6(HBA2):c.230T>C(p.Met77Thr) variant causes a missense change. The variant allele was found at a frequency of 0.00000542 in 1,476,148 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another nucleotide change resulting in same amino acid change has been previously reported as Likely benignin UniProt. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M77K) has been classified as Likely benign.

Frequency

Genomes: 𝑓 0.000029 ( 0 hom., cov: 22)

Exomes 𝑓: 0.0000030 ( 0 hom. )

Consequence

HBA2
NM_000517.6 missense

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 5.72

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 1 ACMG points.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.786

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
HBA2	NM_000517.6 linkuse as main transcript	c.230T>C	p.Met77Thr	missense_variant	2/3	ENST00000251595.11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris
HBA2	ENST00000251595.11 linkuse as main transcript	c.230T>C	p.Met77Thr	missense_variant	2/3	1	NM_000517.6	P1
HBA2	ENST00000484216.1 linkuse as main transcript	c.200T>C	p.Met67Thr	missense_variant	2/2	1
HBA2	ENST00000482565.1 linkuse as main transcript	n.366T>C		non_coding_transcript_exon_variant	1/2	1
HBA2	ENST00000397806.1 linkuse as main transcript	c.134T>C	p.Met45Thr	missense_variant	2/3	2

Frequencies

GnomAD3 genomes

AF:

0.0000294

AC:

AN:

136076

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000970

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000705

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

GnomAD4 exome

AF:

0.00000298

AC:

AN:

1340072

Hom.:

Cov.:

AF XY:

0.00000301

AC XY:

AN XY:

665250

show subpopulations

Gnomad4 AFR exome

AF:

0.0000378

Gnomad4 AMR exome

AF:

0.0000265

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00

Gnomad4 OTH exome

AF:

0.0000358

GnomAD4 genome

AF:

0.0000294

AC:

AN:

136076

Hom.:

Cov.:

AF XY:

0.0000304

AC XY:

AN XY:

65870

show subpopulations

Gnomad4 AFR

AF:

0.0000970

Gnomad4 AMR

AF:

0.0000705

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

Bravo

AF:

0.0000416

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Feb 23, 2023

The c.230T>C (p. Met77Thr) variant (Hb Aztec) is reported with normal clinical presentation in heterozygous state and associated with normal function. The frequency of this variant in the general population, 0.000006 (1/167268 chromosomes, http://gnomad.broadinstitute.org), is uninformative in assessment of its pathogenicity. In the published literature, the variant has been reported in a female infant and her mother, with normal hematological indices (PMID: 3935608 (1985)). Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded conflicting predictions that this variant is deleterious or benign. 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

Pathogenic

0.18

BayesDel_noAF

Uncertain

0.020

Cadd

Benign

Dann

Benign

0.74

Eigen

Benign

-0.23

Eigen_PC

Benign

-0.22

FATHMM_MKL

Pathogenic

0.98

M_CAP

Pathogenic

0.44

MetaRNN

Pathogenic

0.79

D;D

MetaSVM

Uncertain

0.29

MutationTaster

Benign

0.86

N;N

PrimateAI

Uncertain

0.64

PROVEAN

Uncertain

-2.9

D;D

REVEL

Uncertain

0.52

Sift

Pathogenic

0.0

D;D

Sift4G

Pathogenic

0.0010

D;D

Vest4

0.48

MutPred

0.58

Loss of stability (P = 0.0543);.;

MVP

0.99

MPC

1.7

ClinPred

0.87

GERP RS

4.2

gMVP

0.83

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

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