chr8-89982718-ATACCAGGTTGGT-A

Position:

• chr8-89982718-ATACCAGGTTGGT-A

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_002485.5(NBN):​c.163_171+3delACCAACCTGGTA​(p.Thr55_Leu57del) variant causes a splice donor, conservative inframe deletion, splice region, intron change. The variant allele was found at a frequency of 0.000000685 in 1,459,762 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: NBN NM_002485.5 splice_donor, conservative_inframe_deletion, splice_region, intron
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 6.66

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]

NBN (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.058719646 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.9, offset of 0 (no position change), new splice context is: tctGTatgt. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 8-89982718-ATACCAGGTTGGT-A is Pathogenic according to our data. Variant chr8-89982718-ATACCAGGTTGGT-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 370793.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.163_171+3delACCAACCTGGTA	p.Thr55_Leu57del	splice_donor_variant, conservative_inframe_deletion, splice_region_variant, intron_variant	2/16	ENST00000265433.8	NP_002476.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NBN	ENST00000265433.8	c.163_171+3delACCAACCTGGTA	p.Thr55_Leu57del	splice_donor_variant, conservative_inframe_deletion, splice_region_variant, intron_variant	2/16	1	NM_002485.5	ENSP00000265433.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1459762 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 726374

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: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Apr 15, 2016	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Mar 30, 2022	In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 370793). 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 variant results in the deletion of part of exon 2 (c.163_171+3del) of the NBN gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in NBN are known to be pathogenic (PMID: 9590180, 16415040). -

Aplastic anemia Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Apr 04, 2023

- -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Mar 20, 2024

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); This variant is associated with the following publications: (PMID: 34933735, 37453313, 29760218) -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 06, 2019

The c.163_171+3del12 variant results from a deletion of 12 coding nucleotides at the 3' end of coding exon 2 in the NBN gene. This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD) (Lek M et al. Nature, 2016 08;536:285-91). Using the BDGP and ESEfinder splice site prediction tools, this alteration is predicted to weaken this splice donor site. RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). This alteration is expected to result in loss of function due to an abnormal transcript, a translational frameshift leading to premature truncation, or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs1057516772; hg19: chr8-90994946;