chr8-89970380-T-A

Variant names:

• chr8-89970380-T-A
• rs746381477
• NM_002485.5:c.880A>T

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_002485.5(NBN):​c.880A>T​(p.Met294Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,459,192 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 17/22 in silico tools predict a benign 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. M294I) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: NBN NM_002485.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: 0.387
• Publications: 2 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 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.089546084).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_002485.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	NBN	NM_002485.5	MANE Select	c.880A>T	p.Met294Leu	missense	Exon 7 of 16	NP_002476.2
	NBN	NM_001024688.3		c.634A>T	p.Met212Leu	missense	Exon 8 of 17	NP_001019859.1
	NBN	NM_001440379.1		c.634A>T	p.Met212Leu	missense	Exon 7 of 16	NP_001427308.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	NBN	ENST00000265433.8	TSL:1 MANE Select	c.880A>T	p.Met294Leu	missense	Exon 7 of 16	ENSP00000265433.4
	NBN	ENST00000697309.1		c.880A>T	p.Met294Leu	missense	Exon 7 of 15	ENSP00000513244.1
	NBN	ENST00000697293.1		c.880A>T	p.Met294Leu	missense	Exon 7 of 17	ENSP00000513230.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251182 AF XY: 0.00

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 FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1459192 Hom.: 0 Cov.: 31 AF XY: 0.00000413 AC XY: 3 AN XY: 726158

African (AFR) AF: 0.00 AC: 0 AN: 33382

American (AMR) AF: 0.00 AC: 0 AN: 44706

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26116

East Asian (EAS) AF: 0.00 AC: 0 AN: 39664

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86206

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53316

Middle Eastern (MID) AF: 0.000173 AC: 1 AN: 5768

European-Non Finnish (NFE) AF: 9.01e-7 AC: 1 AN: 1109724

Other (OTH) AF: 0.0000166 AC: 1 AN: 60310

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000756

ExAC AF: 0.00000824 AC: 1

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Uncertain:3

Mar 06, 2020

Natera, Inc.

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

Oct 08, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces methionine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 294 of the NBN protein (p.Met294Leu). This variant is present in population databases (rs746381477, gnomAD 0.0009%). This missense change has been observed in individual(s) with breast and/or ovarian cancer (PMID: 26315354, 31273614). ClinVar contains an entry for this variant (Variation ID: 187162). An algorithm developed to predict the effect of missense changes on protein structure and function outputs the following: PolyPhen-2: "Benign". The leucine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. 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.

May 18, 2021

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

not provided Uncertain:1

Oct 19, 2017

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is denoted NBN c.880A>T at the cDNA level, p.Met294Leu (M294L) at the protein level, and results in the change of a Methionine to a Leucine (ATG>TTG). This variant has not, to our knowledge, been published in the literature as pathogenic or benign. NBN Met294Leu was not observed at a significant allele frequency in large population cohorts (Lek 2016). Since Methionine and Leucine share similar properties, this is considered a conservative amino acid substitution. NBN Met294Leu occurs at a position where amino acids with properties similar to Methionine are tolerated across species and is located within the BRCT 2 domain (Damiola 2014). In silico analyses predict that this variant is unlikely to alter protein structure or function. Based on currently available evidence, it is unclear whether NBN Met294Leu is a pathogenic or benign variant. We consider it to be a variant of uncertain significance.

Hereditary cancer-predisposing syndrome Uncertain:1

Sep 07, 2025

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.M294L variant (also known as c.880A>T), located in coding exon 7 of the NBN gene, results from an A to T substitution at nucleotide position 880. The methionine at codon 294 is replaced by leucine, an amino acid with highly similar properties. This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.11
BayesDel_addAF	Benign	-0.27	T
BayesDel_noAF	Benign	-0.62
CADD	Benign	7.0
DANN	Benign	0.56
DEOGEN2	Benign	0.065	T
Eigen	Benign	-0.90
Eigen_PC	Benign	-0.78
FATHMM_MKL	Benign	0.44	N
LIST_S2	Benign	0.54	T
M_CAP	Benign	0.0039	T
MetaRNN	Benign	0.090	T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	0.66	N
PhyloP100		0.39
PrimateAI	Benign	0.43	T
PROVEAN	Benign	-0.66	N
REVEL	Benign	0.085
Sift	Benign	0.88	T
Sift4G	Benign	0.37	T
Polyphen		0.0	B
Vest4		0.21
MutPred		0.51		Loss of MoRF binding (P = 0.094)
MVP		0.57
MPC		0.064
ClinPred		0.031	T
GERP RS		0.068
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.035
gMVP		0.34
Mutation Taster		=97/3	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: rs746381477; hg19: chr8-90982608;