8-89978325-T-A

Position:

• chr8-89978325-T-A

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PVS1 PP5_Very_Strong

The ENST00000265433.8(NBN):​c.481-2A>T variant causes a splice acceptor change. The variant allele was found at a frequency of 0.00000489 in 1,430,462 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000049 (0 hom.)
• Consequence: NBN ENST00000265433.8 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:9
• Conservation: PhyloP100: 5.63

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 Pathogenic. Variant got 16 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PP5: Variant 8-89978325-T-A is Pathogenic according to our data. Variant chr8-89978325-T-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 451148.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NBN	NM_002485.5	c.481-2A>T		splice_acceptor_variant		ENST00000265433.8	NP_002476.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NBN	ENST00000265433.8	c.481-2A>T		splice_acceptor_variant		1	NM_002485.5	ENSP00000265433	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.0000120 AC: 3 AN: 250980 Hom.: 0 AF XY: 0.0000147 AC XY: 2 AN XY: 135688

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.000198

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000881

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000489 AC: 7 AN: 1430462 Hom.: 0 Cov.: 27 AF XY: 0.00000561 AC XY: 4 AN XY: 713278

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.0000771

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000461

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000468 Hom.: 0

ExAC AF: 0.00000824 AC: 1

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:9

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 09, 2024	This sequence change affects an acceptor splice site in intron 4 of the NBN gene. RNA analysis indicates that disruption of this splice site induces altered splicing and may result in an absent or disrupted protein product. This variant is present in population databases (rs751567476, gnomAD 0.02%). This variant has not been reported in the literature in individuals affected with NBN-related conditions. ClinVar contains an entry for this variant (Variation ID: 451148). Studies have shown that disruption of this splice site results in skipping of exon 5 and introduces a premature termination codon (Invitae). The resulting mRNA is expected to undergo nonsense-mediated decay. For these reasons, this variant has been classified as Pathogenic. -
Likely pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Mar 12, 2018	Variant summary: NBN c.481-2A>T is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Five predict the variant abolishes a 3' acceptor site. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 1.2e-05 in 245872 control chromosomes. This frequency is not higher than expected for a pathogenic variant in NBN causing Nijmegen Breakage Syndrome (1.2e-05 vs 0.0025), allowing no conclusion about variant significance. To our knowledge, no occurrence of c.481-2A>T in individuals affected with Nijmegen Breakage Syndrome and no experimental evidence demonstrating its impact on protein function have been reported. Three clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, and all classified the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Dec 03, 2022	This variant disrupts a canonical splice-acceptor site and is predicted to interfere with normal NBN mRNA splicing. The frequency of this variant in the general population, 0.000012 (3/250980 chromosomes, http://gnomad.broadinstitute.org), is uninformative in assessment of its pathogenicity. In the published literature, the variant has been reported in a homozygous state in an individual with stomach cancer (PMID: 34251444 (2021)). Based on the available information, this variant is classified as likely pathogenic. -
Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Feb 03, 2023	Canonical splice site variant predicted to result in a null allele in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); Observed in an individual with esophagogastric cancer (Ku et al., 2021); This variant is associated with the following publications: (PMID: 29922827, 16415040, 9590180, 34251444) -

Hereditary cancer-predisposing syndrome Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	Jan 10, 2024	The c.481-2A>T intronic variant results from an A to T substitution two nucleotides upstream from coding exon 5 in the NBN gene. This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice acceptor site and may result in the creation or strengthening of a novel splice acceptor site; however, direct evidence is insufficient at this time (Ambry internal data). Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. As such, this alteration is classified as likely pathogenic. -
Likely pathogenic, criteria provided, single submitter	curation	Sema4, Sema4	Oct 06, 2020	- -

Aplastic anemia;C0023449:Acute lymphoid leukemia;C0398791:Microcephaly, normal intelligence and immunodeficiency Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Jan 13, 2022

- -

Aplastic anemia Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Mar 12, 2024

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.62	D
BayesDel_noAF	Pathogenic	0.33
CADD	Pathogenic	33
DANN	Uncertain	0.99
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.96
FATHMM_MKL	Pathogenic	0.99	D
MutationTaster	Benign	1.0	D;D
GERP RS		5.8

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.43		Position offset: -41
DS_AL_spliceai		1.0		Position offset: -2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs751567476; hg19: chr8-90990553;