8-89947822-ACAGAT-A

Position:

• chr8-89947822-ACAGAT-A

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PVS1_Moderate PM2 PP5

The NM_002485.5(NBN):​c.1911_1914+1del variant causes a splice donor, coding sequence change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 32)
• Consequence: NBN NM_002485.5 splice_donor, coding_sequence
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:2
• Conservation: PhyloP100: 2.40

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 5 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.030022075 fraction of the gene. Cryptic splice site detected, with MaxEntScore 4, offset of -14, new splice context is: atgGTcagc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 8-89947822-ACAGAT-A is Pathogenic according to our data. Variant chr8-89947822-ACAGAT-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 492105.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NBN	NM_002485.5	c.1911_1914+1del		splice_donor_variant, coding_sequence_variant	12/16	ENST00000265433.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
NBN	ENST00000265433.8	c.1911_1914+1del		splice_donor_variant, coding_sequence_variant	12/16	1	NM_002485.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Microcephaly, normal intelligence and immunodeficiency Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Nov 04, 2023	This variant results in the deletion of part of exon 12 (c.1911_1914+1del) 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). This variant is not present in population databases (gnomAD no frequency). 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: 492105). 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. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -

Hereditary cancer-predisposing syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Dec 08, 2020	This variant deletes 5 nucleotides at the exon 12/intron 12 junction of the NBN gene. This variant may have a significant impact on RNA splicing and may cause the skipping of exon 12, which would result in an in-frame deletion of 23 amino acids. However, this prediction has not been confirmed in published RNA studies. To our knowledge, this variant has not been reported in individuals affected with hereditary cancer in the literature. This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). While this variant is expected to disrupt the splice donor site of intron 12, the impact on the encoded protein has not been determined. Conflicting classifications have been reported for variants affecting the same splice site (ClinVar variation ID: 492105, 802418). In addition, to our knowledge, there is no experimental or clinical evidence indicating that exon 12 is associated with critical NBN function or NBN-related diseases. The available evidence is insufficient to determine the role of this variant in disease conclusively based on the ACMG guideline (PMID: 30192042). Therefore, this variant is classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Oct 03, 2022	The c.1911_1914+1delATCTG intronic variant results from a deletion of 5 nucleotides between positions 1911 and 1914+1 and involves the canonical splice donor site after coding exon 12 of the NBN gene. This nucleotide region is generally well conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). The resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNA decay. The exact functional effect of the altered amino acid sequence is unknown. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

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: rs1554556880; hg19: chr8-90960050;