11-5226654-C-G

Position:

• chr11-5226654-C-G

Variant summary

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

The NM_000518.5(HBB):​c.238G>C​(p.Asp80His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D80Y) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: HBB NM_000518.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1 O:1
• Conservation: PhyloP100: 7.35

Genes affected

HBB (HGNC:4827): (hemoglobin subunit beta) The alpha (HBA) and beta (HBB) loci determine the structure of the 2 types of polypeptide chains in adult hemoglobin, Hb A. The normal adult hemoglobin tetramer consists of two alpha chains and two beta chains. Mutant beta globin causes sickle cell anemia. Absence of beta chain causes beta-zero-thalassemia. Reduced amounts of detectable beta globin causes beta-plus-thalassemia. The order of the genes in the beta-globin cluster is 5'-epsilon -- gamma-G -- gamma-A -- delta -- beta--3'. [provided by RefSeq, Jul 2008]

HBB (HGNC:):

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, 0.986

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HBB	NM_000518.5	c.238G>C	p.Asp80His	missense_variant	2/3	ENST00000335295.4	NP_000509.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HBB	ENST00000335295.4	c.238G>C	p.Asp80His	missense_variant	2/3	1	NM_000518.5	ENSP00000333994.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 36

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1 Other:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Apr 10, 2019

The Hb Tigraye (HBB: c.238G>C; p.Asp80His, also known as Asp79His when numbered from the mature protein; rs33990858) is reported in the literature in several healthy individuals with normal hematology (Pistidda 2001, HbVar and references therein). This variant is reported in ClinVar (Variation ID: 15522), but it is absent from general population databases (Exome Variant Server, Genome Aggregation Database), indicating it is not a common polymorphism. The aspartate at codon 80 is highly conserved, and computational analyses (SIFT, PolyPhen-2) predict that this variant is deleterious, though these are low-confidence predictions. Additionally, other amino acid substitutions at this codon (Asn, Tyr, Gly, and Ala) have been reported in clinically normal individuals, including a healthy individual homozygous for the p.Asp80Tyr variant (Lehmann 1964, HbVar database), and are not reported in association with disease, suggesting missense variants at this codon may be tolerated. However, studies in separate families by two groups measured increased oxygen affinity in Hb Tigraye (Pistidda 2001; Molchanova 1993). Although erythrocyte indices were normal in carriers, it is uncertain what the effect would be in combination with a beta-thalassemia variant. Given the lack of clinical and functional data, the significance of the p.Asp80His variant is uncertain at this time. References: HbVar link to Hb Tigraye: http://globin.bx.psu.edu/cgi-bin/hbvar/query_vars3?mode=output&display_format=page&i=400 Lehmann H et al. Haemoglobin GACCRA. Nature. 1964; 203:363-5. Molchanova TP et al. Hb Tigraye or alpha 2 beta (2)79(EF3)Asp-->His(GAC-->CAC): a hemoglobin variant with increased oxygen affinity observed in an Ethiopian male. Hemoglobin. 1993 Jun;17(3):247-50. Pistidda P et al. Hb Tigraye [beta79(EF3)Asp --> His] in a Caucasian family from Sardinia. Hemoglobin. 2001 Aug;25(3):341-5. -

HEMOGLOBIN TIGRAYE Other:1

other, no assertion criteria provided

literature only

OMIM

Dec 12, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.69
BayesDel_addAF	Pathogenic	0.53	D
BayesDel_noAF	Pathogenic	0.52
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Benign	0.14	T;T;.;T
Eigen	Pathogenic	0.79
Eigen_PC	Pathogenic	0.69
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.91	.;D;D;D
M_CAP	Pathogenic	0.35	D
MetaRNN	Pathogenic	0.99	D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.2	H;H;.;.
PrimateAI	Uncertain	0.63	T
PROVEAN	Pathogenic	-6.0	D;.;.;D
REVEL	Pathogenic	0.91
Sift	Pathogenic	0.0	D;.;.;D
Sift4G	Uncertain	0.0060	D;.;.;.
Polyphen		0.99	D;D;.;.
Vest4		0.98
MutPred		0.92		Gain of ubiquitination at K83 (P = 0.0762);Gain of ubiquitination at K83 (P = 0.0762);Gain of ubiquitination at K83 (P = 0.0762);Gain of ubiquitination at K83 (P = 0.0762);
MVP		0.99
MPC		0.073
ClinPred		0.99	D
GERP RS		5.1
Varity_R		0.79
gMVP		0.85

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: rs33990858; hg19: chr11-5247884;