8-89978224-C-T

Variant names:

• chr8-89978224-C-T
• rs1554566610
• NM_002485.5:c.580G>A

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 4P and 1B. PM1 PM2 BP4

The NM_002485.5(NBN):​c.580G>A​(p.Glu194Lys) variant causes a missense 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. Variant has been reported in ClinVar as Uncertain significance (★★). Synonymous variant affecting the same amino acid position (i.e. E194E) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: NBN NM_002485.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 3.30
• Publications: 0 publications found

Genes affected

NBN (HGNC:7652): (nibrin) Mutations in this gene are associated with Nijmegen breakage syndrome, an autosomal recessive chromosomal instability syndrome characterized by microcephaly, growth retardation, immunodeficiency, and cancer predisposition. The encoded protein is a member of the MRE11/RAD50 double-strand break repair complex which consists of 5 proteins. This gene product is thought to be involved in DNA double-strand break repair and DNA damage-induced checkpoint activation. [provided by RefSeq, Jul 2008]

NBN Gene-Disease associations (from GenCC):

• Nijmegen breakage syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: G2P, Orphanet, Labcorp Genetics (formerly Invitae), ClinGen, Myriad Women’s Health
• rhabdomyosarcoma

  Inheritance: AR Classification: MODERATE Submitted by: Genomics England PanelApp
• idiopathic aplastic anemia

  Inheritance: AD Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)
• prostate cancer

  Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics
• hereditary breast carcinoma

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

ACMG classification

Our verdict: Uncertain_significance. The variant received 3 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 35 uncertain in NM_002485.5
• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.32054567).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
NBN	NM_002485.5	c.580G>A	p.Glu194Lys	missense_variant	Exon 5 of 16	ENST00000265433.8	NP_002476.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
NBN	ENST00000265433.8	c.580G>A	p.Glu194Lys	missense_variant	Exon 5 of 16	1	NM_002485.5	ENSP00000265433.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Uncertain:1

Aug 10, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamic acid with lysine at codon 194 of the NBN protein (p.Glu194Lys). The glutamic acid residue is highly conserved and there is a small physicochemical difference between glutamic acid and lysine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with NBN-related disease. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Hereditary cancer-predisposing syndrome Uncertain:1

Sep 16, 2021

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.E194K variant (also known as c.580G>A), located in coding exon 5 of the NBN gene, results from a G to A substitution at nucleotide position 580. The glutamic acid at codon 194 is replaced by lysine, an amino acid with similar properties. This amino acid position is conserved. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.13
BayesDel_addAF	Uncertain	0.058	T
BayesDel_noAF	Benign	-0.15
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Benign	0.17	T;T;.
Eigen	Pathogenic	0.70
Eigen_PC	Pathogenic	0.71
FATHMM_MKL	Uncertain	0.89	D
LIST_S2	Benign	0.84	T;T;T
M_CAP	Benign	0.035	D
MetaRNN	Benign	0.32	T;T;T
MetaSVM	Uncertain	-0.14	T
MutationAssessor	Pathogenic	3.0	M;.;.
PhyloP100		3.3
PrimateAI	Benign	0.46	T
PROVEAN	Benign	-2.2	N;N;D
REVEL	Benign	0.17
Sift	Uncertain	0.0090	D;D;D
Sift4G	Uncertain	0.025	D;D;.
Polyphen		0.99	D;.;.
Vest4		0.34
MutPred		0.24		Gain of methylation at E194 (P = 0.0037);.;.;
MVP		0.89
MPC		0.084
ClinPred		0.96	D
GERP RS		6.0
Varity_R		0.23
gMVP		0.64
Mutation Taster		=76/24	polymorphism

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

Other links and lift over

dbSNP: rs1554566610; hg19: chr8-90990452;