rs33964507

Positions:

• chr16-176799-A-C
• chr16-176799-A-G
• chr16-176799-A-T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_000558.5(HBA1):​c.83A>C​(p.Glu28Ala) 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 variant affecting the same amino acid position, but resulting in a different missense (i.e. E28D) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 28)
  • Exomes 𝑓: 7.1e-7 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: HBA1 NM_000558.5 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 6.22

Genes affected

HBA1 (HGNC:4823): (hemoglobin subunit alpha 1) 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 Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.979

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
HBA1	NM_000558.5	c.83A>C	p.Glu28Ala	missense_variant	1/3	ENST00000320868.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
HBA1	ENST00000320868.9	c.83A>C	p.Glu28Ala	missense_variant	1/3	1	NM_000558.5	P1
HBA1	ENST00000472694.1	n.102A>C		non_coding_transcript_exon_variant	1/2	1
HBA1	ENST00000487791.1	n.52A>C		non_coding_transcript_exon_variant	1/2	1
HBA1	ENST00000397797.1	c.-2+37A>C		intron_variant		2

Frequencies

GnomAD3 genomes Cov.: 28

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 7.10e-7 AC: 1 AN: 1409316 Hom.: 0 Cov.: 25 AF XY: 0.00000143 AC XY: 1 AN XY: 699440

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: 0.0000122

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 28

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.49
BayesDel_addAF	Pathogenic	0.28	D
BayesDel_noAF	Pathogenic	0.17
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Benign	0.30	T
Eigen	Uncertain	0.24
Eigen_PC	Uncertain	0.25
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.95	D
M_CAP	Pathogenic	0.96	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Uncertain	0.77	D
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.57	T
PROVEAN	Pathogenic	-5.7	D
REVEL	Pathogenic	0.88
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.0060	D
Vest4		0.54
MutPred		0.91		Loss of disorder (P = 0.0638);
MVP		1.0
ClinPred		1.0	D
GERP RS		4.5
Varity_R		0.91
gMVP		0.84

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: rs33964507; hg19: chr16-226798;