8-89955379-G-T

Variant names:

• chr8-89955379-G-T
• rs757452107
• NM_002485.5:c.1301C>A

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_002485.5(NBN):​c.1301C>A​(p.Thr434Asn) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,552 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/22 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. T434S) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: NBN NM_002485.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.0350
• Publications: 5 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: Likely_benign. The variant received -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.0574345).

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.1301C>A	p.Thr434Asn	missense	Exon 10 of 16	NP_002476.2
	NBN	NM_001024688.3		c.1055C>A	p.Thr352Asn	missense	Exon 11 of 17	NP_001019859.1
	NBN	NM_001440379.1		c.1055C>A	p.Thr352Asn	missense	Exon 10 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.1301C>A	p.Thr434Asn	missense	Exon 10 of 16	ENSP00000265433.4
	NBN	ENST00000697309.1		c.1301C>A	p.Thr434Asn	missense	Exon 10 of 15	ENSP00000513244.1
	NBN	ENST00000697293.1		c.1301C>A	p.Thr434Asn	missense	Exon 10 of 17	ENSP00000513230.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461552 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727096

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

African (AFR) AF: 0.00 AC: 0 AN: 33472

American (AMR) AF: 0.00 AC: 0 AN: 44718

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26124

East Asian (EAS) AF: 0.00 AC: 0 AN: 39688

South Asian (SAS) AF: 0.00 AC: 0 AN: 86250

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53408

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5764

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111744

Other (OTH) AF: 0.00 AC: 0 AN: 60384

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Uncertain:2

Nov 07, 2021

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Nov 26, 2020

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. This sequence change replaces threonine with asparagine at codon 434 of the NBN protein (p.Thr434Asn). The threonine residue is weakly conserved and there is a small physicochemical difference between threonine and asparagine. 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. ClinVar contains an entry for this variant (Variation ID: 187536). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The asparagine amino acid residue is found in multiple mammalian species, suggesting that this missense change does not adversely affect protein function. These predictions have not been confirmed by published functional studies and their clinical significance is uncertain.

Hereditary cancer-predisposing syndrome Uncertain:1

May 20, 2025

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.T434N variant (also known as c.1301C>A), located in coding exon 10 of the NBN gene, results from a C to A substitution at nucleotide position 1301. The threonine at codon 434 is replaced by asparagine, an amino acid with 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	0.085
BayesDel_addAF	Benign	-0.27	T
BayesDel_noAF	Benign	-0.63
CADD	Benign	8.0
DANN	Benign	0.96
DEOGEN2	Benign	0.088	T
Eigen	Benign	-0.65
Eigen_PC	Benign	-0.74
FATHMM_MKL	Benign	0.042	N
LIST_S2	Benign	0.54	T
M_CAP	Benign	0.013	T
MetaRNN	Benign	0.057	T
MetaSVM	Benign	-1.0	T
MutationAssessor	Uncertain	2.3	M
PhyloP100		0.035
PrimateAI	Benign	0.27	T
PROVEAN	Benign	-0.83	N
REVEL	Benign	0.10
Sift	Benign	0.095	T
Sift4G	Benign	0.24	T
Polyphen		0.70	P
Vest4		0.048
MutPred		0.11		Loss of glycosylation at T434 (P = 0.0677)
MVP		0.69
MPC		0.077
ClinPred		0.079	T
GERP RS		-0.25
Varity_R		0.13
gMVP		0.21
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: rs757452107; hg19: chr8-90967607;