rs63751238

chr16-173331-T-A

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1 PM2 PP3_Strong

The NM_000517.6(HBA2):c.300+2T>A variant causes a splice donor change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000696 in 1,436,438 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency:
  • Genomes: not found (cov: 24)
  • Exomes 𝑓: 7.0e-7 (0 hom.)
• Consequence: HBA2 NM_000517.6 splice_donor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 2.19

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 Pathogenic. Variant got 14 ACMG points.

• PVS1: Splicing variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
HBA2	NM_000517.6	c.300+2T>A		splice_donor_variant		ENST00000251595.11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
HBA2	ENST00000251595.11	c.300+2T>A		splice_donor_variant		1	NM_000517.6	P1
HBA2	ENST00000484216.1	c.272T>A	p.Val91Glu	missense_variant	2/2	1
HBA2	ENST00000482565.1	n.436+2T>A		splice_donor_variant, non_coding_transcript_variant		1
HBA2	ENST00000397806.1	c.204+2T>A		splice_donor_variant		2

Frequencies

GnomAD3 genomes Cov.: 24

GnomAD3 exomes AF: 0.00000448 AC: 1 AN: 223156 Hom.: 0 AF XY: 0.00000811 AC XY: 1 AN XY: 123296

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000981

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.96e-7 AC: 1 AN: 1436438 Hom.: 0 Cov.: 31 AF XY: 0.00000140 AC XY: 1 AN XY: 714708

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.06e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 24

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.60	D
BayesDel_noAF	Benign	-0.11
Cadd	Uncertain	25
Dann	Benign	0.95
Eigen	Pathogenic	0.68
Eigen_PC	Uncertain	0.43
FATHMM_MKL	Uncertain	0.95	D
MutationTaster	Benign	1.0	D;D
GERP RS		4.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.89
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.99		Position offset: -2

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

Publications

LitVar

Other links and lift over

dbSNP: rs63751238; hg19: chr16-223330;