chr8-89947838-C-T

Position:

• chr8-89947838-C-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_002485.5(NBN):​c.1900G>A​(p.Ala634Thr) 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. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: NBN NM_002485.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:1
• Conservation: PhyloP100: 0.327

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 (HGNC:):

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.012757838).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NBN	NM_002485.5	c.1900G>A	p.Ala634Thr	missense_variant	12/16	ENST00000265433.8	NP_002476.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NBN	ENST00000265433.8	c.1900G>A	p.Ala634Thr	missense_variant	12/16	1	NM_002485.5	ENSP00000265433.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1424646 Hom.: 0 Cov.: 26 AF XY: 0.00 AC XY: 0 AN XY: 709398

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 18, 2021

In summary, this variant is a novel missense change that is not predicted to affect protein function. There is no indication that it causes disease, but the available evidence is currently insufficient to prove that conclusively. Therefore, it has been classified as a Variant of Uncertain Significance. 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 threonine 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. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a NBN-related disease. This sequence change replaces alanine with threonine at codon 634 of the NBN protein (p.Ala634Thr). The alanine residue is weakly conserved and there is a small physicochemical difference between alanine and threonine. -

Hereditary cancer-predisposing syndrome Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 08, 2024

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.061
BayesDel_addAF	Benign	-0.30	T
BayesDel_noAF	Benign	-0.66
CADD	Benign	11
DANN	Benign	0.29
DEOGEN2	Benign	0.042	T;T;.
Eigen	Benign	-1.5
Eigen_PC	Benign	-1.4
FATHMM_MKL	Benign	0.00065	N
LIST_S2	Benign	0.34	T;T;T
M_CAP	Benign	0.0068	T
MetaRNN	Benign	0.013	T;T;T
MetaSVM	Benign	-1.1	T
MutationAssessor	Benign	-1.8	N;.;.
PrimateAI	Benign	0.38	T
PROVEAN	Benign	0.36	N;N;.
REVEL	Benign	0.046
Sift	Benign	1.0	T;T;.
Sift4G	Benign	0.66	T;T;T
Polyphen		0.0	B;.;.
Vest4		0.092
MutPred		0.14		Loss of stability (P = 0.063);.;.;
MVP		0.48
MPC		0.065
ClinPred		0.034	T
GERP RS		0.89
Varity_R		0.022
gMVP		0.046

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs1554556892; hg19: chr8-90960066;