rs772059959

Positions:

• chr8-89943366-C-A
• chr8-89943366-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The ENST00000265433.8(NBN):​c.2071G>T​(p.Val691Phe) variant causes a missense, splice region change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 2/3 splice prediction tools predicting alterations to normal splicing. 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. V691G) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: NBN ENST00000265433.8 missense, splice_region
• Scores: Splicing: ADA: 0.9995
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 2.66

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 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NBN	NM_002485.5	c.2071G>T	p.Val691Phe	missense_variant, splice_region_variant	14/16	ENST00000265433.8	NP_002476.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NBN	ENST00000265433.8	c.2071G>T	p.Val691Phe	missense_variant, splice_region_variant	14/16	1	NM_002485.5	ENSP00000265433	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

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

Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Feb 27, 2020	Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Probably Damaging"; 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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. This variant has not been reported in the literature in individuals with NBN-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces valine with phenylalanine at codon 691 of the NBN protein (p.Val691Phe). The valine residue is weakly conserved and there is a small physicochemical difference between valine and phenylalanine. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 30, 2022

The p.V691F variant (also known as c.2071G>T) is located in coding exon 14 of the NBN gene. The valine at codon 691 is replaced by phenylalanine, an amino acid with highly similar properties. This change occurs in the first base pair of coding exon 14. This amino acid position is 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	0.21
BayesDel_addAF	Benign	0.0076	T
BayesDel_noAF	Benign	-0.23
CADD	Uncertain	24
DANN	Uncertain	0.99
DEOGEN2	Benign	0.39	T;T;.
Eigen	Uncertain	0.30
Eigen_PC	Uncertain	0.26
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Uncertain	0.89	D;D;T
M_CAP	Benign	0.073	D
MetaRNN	Uncertain	0.48	T;T;T
MetaSVM	Benign	-0.36	T
MutationAssessor	Uncertain	2.3	M;.;.
MutationTaster	Benign	0.97	D;D
PrimateAI	Uncertain	0.50	T
PROVEAN	Benign	-2.3	N;D;.
REVEL	Uncertain	0.37
Sift	Uncertain	0.0040	D;D;.
Sift4G	Benign	0.10	T;T;D
Polyphen		1.0	D;.;.
Vest4		0.57
MutPred		0.54		Loss of helix (P = 0.0033);.;.;
MVP		0.77
MPC		0.45
ClinPred		0.93	D
GERP RS		3.8
Varity_R		0.24
gMVP		0.43

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.070		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: rs772059959; hg19: chr8-90955594;