rs786202464

Positions:

• chr17-31182600-A-C
• chr17-31182600-A-G
• chr17-31182600-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 5P and 1B. PM1 PM2 PP2 BP4

The ENST00000358273.9(NF1):​c.823A>C​(p.Ile275Leu) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,730 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I275F) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: NF1 ENST00000358273.9 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 3.60

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.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 14 uncertain in ENST00000358273.9
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), NF1. . Gene score misZ 6.5427 (greater than the threshold 3.09). Trascript score misZ 8.4054 (greater than threshold 3.09). GenCC has associacion of gene with neurofibromatosis, familial spinal, hereditary pheochromocytoma-paraganglioma, neurofibromatosis type 1, Watson syndrome, neurofibromatosis-Noonan syndrome, Moyamoya disease, familial ovarian cancer.
• BP4: Computational evidence support a benign effect (MetaRNN=0.27152818).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NF1	NM_001042492.3	c.823A>C	p.Ile275Leu	missense_variant	8/58	ENST00000358273.9	NP_001035957.1
NF1	NM_000267.3	c.823A>C	p.Ile275Leu	missense_variant	8/57		NP_000258.1
NF1	NM_001128147.3	c.823A>C	p.Ile275Leu	missense_variant	8/15		NP_001121619.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NF1	ENST00000358273.9	c.823A>C	p.Ile275Leu	missense_variant	8/58	1	NM_001042492.3	ENSP00000351015	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461730 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727160

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Neurofibromatosis, type 1 Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Mar 15, 2022	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jul 01, 2021	This sequence change replaces isoleucine with leucine at codon 275 of the NF1 protein (p.Ile275Leu). The isoleucine residue is weakly conserved and there is a small physicochemical difference between isoleucine and leucine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with NF1-related conditions. ClinVar contains an entry for this variant (Variation ID: 185796). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt NF1 protein function. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 01, 2016

The p.I275L variant (also known as c.823A>C), located in coding exon 8 of the NF1 gene, results from an A to C substitution at nucleotide position 823. The isoleucine at codon 275 is replaced by leucine, an amino acid with highly similar properties. 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 0.001% (greater than 110000alleles tested) in our clinical cohort.This amino acid position is highly conserved through mammals but not in all available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive.Since supporting evidence is limited at this time, the clinical significance of this alterationremains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.33
BayesDel_addAF	Uncertain	0.047	T
BayesDel_noAF	Benign	-0.17
CADD	Benign	22
DANN	Benign	0.97
DEOGEN2	Uncertain	0.56	.;D;.;.;.
Eigen	Benign	-0.18
Eigen_PC	Benign	-0.041
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Uncertain	0.91	D;D;D;D;D
M_CAP	Pathogenic	0.30	D
MetaRNN	Benign	0.27	T;T;T;T;T
MetaSVM	Benign	-0.65	T
MutationAssessor	Benign	1.8	L;L;L;L;.
MutationTaster	Benign	0.77	D;D;D
PrimateAI	Uncertain	0.73	T
PROVEAN	Benign	-1.2	.;N;N;N;.
REVEL	Benign	0.28
Sift	Benign	0.16	.;T;T;T;.
Sift4G	Uncertain	0.027	.;D;D;T;.
Polyphen		0.0060	B;B;B;.;.
Vest4		0.47, 0.47, 0.53
MutPred		0.31		Gain of helix (P = 0.2294);Gain of helix (P = 0.2294);Gain of helix (P = 0.2294);Gain of helix (P = 0.2294);.;
MVP		0.86
MPC		0.69
ClinPred		0.75	D
GERP RS		2.9
Varity_R		0.075
gMVP		0.41

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.19		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: rs786202464; hg19: chr17-29509618;