chr16-173259-T-A

Position:

• chr16-173259-T-A

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_000517.6(HBA2):​c.230T>A​(p.Met77Lys) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. 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. M77T) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 22)
• Consequence: HBA2 NM_000517.6 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 5.72

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.886

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HBA2	NM_000517.6	c.230T>A	p.Met77Lys	missense_variant	2/3	ENST00000251595.11	NP_000508.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HBA2	ENST00000251595.11	c.230T>A	p.Met77Lys	missense_variant	2/3	1	NM_000517.6	ENSP00000251595	P1
HBA2	ENST00000484216.1	c.200T>A	p.Met67Lys	missense_variant	2/2	1		ENSP00000495899
HBA2	ENST00000482565.1	n.366T>A		non_coding_transcript_exon_variant	1/2	1
HBA2	ENST00000397806.1	c.134T>A	p.Met45Lys	missense_variant	2/3	2		ENSP00000380908

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 25

GnomAD4 genome Cov.: 22

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Benign	22
DANN	Benign	0.94
DEOGEN2	Benign	0.018	.;T
Eigen	Benign	-0.28
Eigen_PC	Benign	-0.25
FATHMM_MKL	Pathogenic	0.98	D
M_CAP	Pathogenic	0.48	D
MetaRNN	Pathogenic	0.89	D;D
MetaSVM	Uncertain	0.53	D
MutationTaster	Benign	0.55	D;N
PrimateAI	Uncertain	0.63	T
PROVEAN	Uncertain	-4.0	D;D
REVEL	Uncertain	0.58
Sift	Pathogenic	0.0	D;D
Sift4G	Pathogenic	0.0	D;D
Vest4		0.54
MutPred		0.66		Gain of ubiquitination at M77 (P = 0.0146);.;
MVP		1.0
MPC		2.0
ClinPred		0.94	D
GERP RS		4.2
gMVP		0.93

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

Other links and lift over

dbSNP: rs281864860; hg19: chr16-223258;