8-89980834-G-C

Position:

• chr8-89980834-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_002485.5(NBN):​c.380C>G​(p.Ala127Gly) 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 1,460,140 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts 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. A127P) 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:3
• Conservation: PhyloP100: 1.85

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.41815507).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NBN	NM_002485.5	c.380C>G	p.Ala127Gly	missense_variant	4/16	ENST00000265433.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
NBN	ENST00000265433.8	c.380C>G	p.Ala127Gly	missense_variant	4/16	1	NM_002485.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1460140 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726510

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000360

Gnomad4 OTH exome AF: 0.00

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:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 31, 2023

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. An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant  is likely to be tolerated. ClinVar contains an entry for this variant (Variation ID: 461560). This variant has not been reported in the literature in individuals affected with NBN-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with glycine, which is neutral and non-polar, at codon 127 of the NBN protein (p.Ala127Gly). -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Sep 06, 2023

This variant has not been reported in the published literature. It also has not been reported in large, multi-ethnic general populations (Genome Aggregation Database, http://gnomad.broadinstitute.org). Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded conflicting predictions that this variant is benign or damaging. Based on the available information, we are unable to determine the clinical significance of this variant. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 06, 2023

The p.A127G variant (also known as c.380C>G), located in coding exon 4 of the NBN gene, results from a C to G substitution at nucleotide position 380. The alanine at codon 127 is replaced by glycine, 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 v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.14
BayesDel_addAF	Benign	-0.070	T
BayesDel_noAF	Benign	-0.34
CADD	Benign	23
DANN	Uncertain	1.0
DEOGEN2	Benign	0.18	T;T;.;.
Eigen	Uncertain	0.23
Eigen_PC	Uncertain	0.28
FATHMM_MKL	Benign	0.71	D
LIST_S2	Uncertain	0.86	D;D;D;D
M_CAP	Benign	0.059	D
MetaRNN	Benign	0.42	T;T;T;T
MetaSVM	Benign	-0.52	T
MutationAssessor	Uncertain	2.0	M;.;.;.
MutationTaster	Benign	0.95	N;N
PrimateAI	Benign	0.30	T
PROVEAN	Uncertain	-2.4	N;N;N;D
REVEL	Benign	0.18
Sift	Uncertain	0.013	D;D;D;T
Sift4G	Benign	0.067	T;T;.;T
Polyphen		0.92	P;.;.;.
Vest4		0.34
MutPred		0.68		Gain of ubiquitination at K125 (P = 0.1008);.;.;.;
MVP		0.90
MPC		0.11
ClinPred		0.83	D
GERP RS		3.6
Varity_R		0.13
gMVP		0.24

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: rs1554567966; hg19: chr8-90993062;