rs786203280

chr17-31156021-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_001042492.3(NF1):c.99A>G(p.Lys33=) variant causes a synonymous change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 32)
• Consequence: NF1 NM_001042492.3 synonymous
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:2
• Conservation: PhyloP100: 7.00

Genes affected

NF1 (HGNC:7765): (neurofibromin 1) This gene product appears to function as a negative regulator of the ras signal transduction pathway. Mutations in this gene have been linked to neurofibromatosis type 1, juvenile myelomonocytic leukemia and Watson syndrome. The mRNA for this gene is subject to RNA editing (CGA>UGA->Arg1306Term) resulting in premature translation termination. Alternatively spliced transcript variants encoding different isoforms have also been described for this gene. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NF1	NM_001042492.3	c.99A>G	p.Lys33=	synonymous_variant	2/58	ENST00000358273.9
NF1	NM_000267.3	c.99A>G	p.Lys33=	synonymous_variant	2/57
NF1	NM_001128147.3	c.99A>G	p.Lys33=	synonymous_variant	2/15

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
NF1	ENST00000358273.9	c.99A>G	p.Lys33=	synonymous_variant	2/58	1	NM_001042492.3	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Neurofibromatosis, type 1 Pathogenic:1 Uncertain:1

Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Jun 04, 2023	For these reasons, this variant has been classified as Pathogenic. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. ClinVar contains an entry for this variant (Variation ID: 186861). This variant has been observed in individual(s) with neurofibromatosis type 1 (PMID: 26740943, 31766501; Invitae). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (gnomAD no frequency). This sequence change affects codon 33 of the NF1 mRNA. It is a 'silent' change, meaning that it does not change the encoded amino acid sequence of the NF1 protein. -
Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Mar 15, 2022	- -

Hereditary cancer-predisposing syndrome;CN230736:Cardiovascular phenotype Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 13, 2019

The c.99A>G variant (also known as p.K33K), located in coding exon 2 of the NF1 gene, results from an A to G substitution at nucleotide position 99. This nucleotide substitution does not change the amino acid at codon 33. However, this change occurs in the last base pair of coding exon 2, which makes it likely to have some effect on normal mRNA splicing. This variant has been identified in multiple individuals with a clinical diagnosis or features of neurofibromatosis type 1 (Bianchessi D et al. Mol Genet Genomic Med, 2015 Nov;3:513-25; Messiaen L et al. JAMA, 2009 Nov;302:2111-8). This nucleotide position is highly conserved in available vertebrate species. Using the BDGP and ESEfinder splice site prediction tools, this alteration is predicted to create a new alternate splice donor site. RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Ambry internal data). Based on the majority of available evidence to date, this variant is likely to be pathogenic. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 23, 2014

The c.99A>G variant (also known as p.K33K) located in coding exon 2, results from an A to G substitution at nucleotide position 99 of the NF1 gene. This nucleotide substitution does not change the amino acid at codon 33. This variant was not reported in population based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 6503 samples (13006 alleles) with coverage at this position. To date, this alteration has been detected with an allele frequency of approximately 0.01% (greater than 11000 alleles tested) in our clinical cohort. This nucleotide position is highly conserved in available vertebrate species. Using the BDGP and ESEfinder splice site prediction tools, this alteration is predicted to create of a new alternate splice donor splice site; however, direct evidence is unavailable. Since supporting evidence is limited at this time, the clinical significance of c.99A>G remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.48
Cadd	Benign	22
Dann	Benign	0.63

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.87		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.87		Position offset: 0

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

Publications

LitVar

Other links and lift over

dbSNP: rs786203280; hg19: chr17-29483039;