16-173008-G-C

Variant names:

• chr16-173008-G-C
• NM_000517.6:c.95+1G>C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_Strong PP5_Moderate

The NM_000517.6(HBA2):​c.95+1G>C variant causes a splice donor, intron change. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency: Genomes: not found (cov: 3)
• Consequence: HBA2 NM_000517.6 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 5.07

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 Likely_pathogenic. Variant got 6 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.30769232 fraction of the gene. Cryptic splice site detected, with MaxEntScore 5.8, offset of -19, new splice context is: atgGTgcgg. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PP5: Variant 16-173008-G-C is Pathogenic according to our data. Variant chr16-173008-G-C is described in ClinVar as [Pathogenic]. Clinvar id is 2921026.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBA2	NM_000517.6	c.95+1G>C		splice_donor_variant, intron_variant	Intron 1 of 2	ENST00000251595.11	NP_000508.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HBA2	ENST00000251595.11	c.95+1G>C		splice_donor_variant, intron_variant	Intron 1 of 2	1	NM_000517.6	ENSP00000251595.6
HBA2	ENST00000484216.1	c.62+1G>C		splice_donor_variant, intron_variant	Intron 1 of 1	1		ENSP00000495899.1
HBA2	ENST00000482565.1	n.115G>C		non_coding_transcript_exon_variant	Exon 1 of 2	1
HBA2	ENST00000397806.1	c.-2+50G>C		intron_variant	Intron 1 of 2	2		ENSP00000380908.1

Frequencies

GnomAD3 genomes Cov.: 3

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 3

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Mar 29, 2024

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The HBA2 c.95+1G>C variant, to our knowledge, is not reported in the medical literature or gene specific databases. This variant is also absent from the Genome Aggregation Database, indicating it is not a common polymorphism. However, other variants at this nucleotide (c.95+1G>A, c.95+1G>T) have been reported in individuals with microcytosis and hypochromia and are considered pathogenic (Waye 2009, HbVar ID: 2597). This variant disrupts the canonical splice donor site of intron 1, which is likely to negatively impact gene function. Based on available information, this variant is considered to be pathogenic. References: Link to HbVar database: https://globin.bx.psu.edu/hbvar/menu.html Waye JS et al. alpha-Thalassemia caused by two novel splice mutations of the alpha2-globin gene: IVS-I-1 (G>A and G>T). Hemoglobin. 2009;33(6):519-22. PMID: 19958200. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.60	D
BayesDel_noAF	Uncertain	0.060
CADD	Pathogenic	34
DANN	Uncertain	0.99
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.81
FATHMM_MKL	Pathogenic	0.99	D
GERP RS		3.9

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.29		Position offset: -50
DS_DL_spliceai		0.99		Position offset: -1

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

Publications

No publications associated with this variant yet.

Other links and lift over

hg19: chr16-223007;