Genetic Variant HBG2:p.Asn20Asn (chr11-5254669-A-G) – ACMG Classification: Likely_benign (-3 pts)

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 2P and 5B. PM2BP4_StrongBP7

The NM_000184.3(HBG2):c.60T>C(p.Asn20Asn) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: not found (cov: 23)

Exomes 𝑓: 0.0000028 ( 0 hom. )

Failed GnomAD Quality Control

Consequence

HBG2
NM_000184.3 synonymous

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -1.18

Publications

1 publications found

Variant links:

Genes affected

HBG2 (HGNC:4832): (hemoglobin subunit gamma 2) The gamma globin genes (HBG1 and HBG2) are normally expressed in the fetal liver, spleen and bone marrow. Two gamma chains together with two alpha chains constitute fetal hemoglobin (HbF) which is normally replaced by adult hemoglobin (HbA) at birth. In some beta-thalassemias and related conditions, gamma chain production continues into adulthood. The two types of gamma chains differ at residue 136 where glycine is found in the G-gamma product (HBG2) and alanine is found in the A-gamma product (HBG1). The former is predominant at birth. 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]

HBG2 Gene-Disease associations (from GenCC):

hemoglobinopathy Toms River
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
hereditary persistence of fetal hemoglobin-beta-thalassemia syndrome
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
hereditary persistence of fetal hemoglobin-sickle cell disease syndrome
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
cyanosis, transient neonatal
Inheritance: Unknown Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)

HBG2 links:

ENSG00000284931 (HGNC:):

ENSG00000284931 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -3 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.92).

BP7

Synonymous conserved (PhyloP=-1.18 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HBG2	NM_000184.3 link	c.60T>C	p.Asn20Asn	synonymous_variant	Exon 1 of 3	ENST00000336906.6	NP_000175.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein
HBG2	ENST00000336906.6 link	c.60T>C	p.Asn20Asn	synonymous_variant	Exon 1 of 3	1	NM_000184.3	ENSP00000338082.4
ENSG00000284931	ENST00000642908.1 link	c.60T>C	p.Asn20Asn	synonymous_variant	Exon 1 of 3			ENSP00000495346.1
ENSG00000239920	ENST00000380259.7 link	n.*1363T>C		non_coding_transcript_exon_variant	Exon 7 of 8	5		ENSP00000369609.3
ENSG00000239920	ENST00000380259.7 link	n.*1363T>C		3_prime_UTR_variant	Exon 7 of 8	5		ENSP00000369609.3

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

Data not reliable, filtered out with message: AS_VQSR

AF:

0.00000281

AC:

AN:

712946

Hom.:

Cov.:

AF XY:

0.00000270

AC XY:

AN XY:

370486

show subpopulations

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

19010

American (AMR)

AF:

0.00

AC:

AN:

32026

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

18536

East Asian (EAS)

AF:

0.00

AC:

AN:

32992

South Asian (SAS)

AF:

0.00

AC:

AN:

60748

European-Finnish (FIN)

AF:

0.00

AC:

AN:

38280

Middle Eastern (MID)

AF:

0.00

AC:

AN:

2650

European-Non Finnish (NFE)

AF:

0.00000422

AC:

AN:

473472

Other (OTH)

AF:

0.00

AC:

AN:

35232

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.0000812204), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.300

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

Cov.:

Alfa

AF:

0.00

Hom.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.92

CADD

Benign

7.5

(source)

DANN

Benign

0.82

PhyloP100

-1.2

PromoterAI

0.060

Neutral

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.020

Details are displayed if max score is > 0.2

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Computational scores

Splicing

Publications

Other links and lift over