X-153868561-C-T

Position:

• chrX-153868561-C-T

Variant summary

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

The NM_001278116.2(L1CAM):​c.1546G>A​(p.Asp516Asn) variant causes a missense, splice region change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 24)
• Consequence: L1CAM NM_001278116.2 missense, splice_region
• Scores: Splicing: ADA: 0.9999
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.08

Genes affected

L1CAM (HGNC:6470): (L1 cell adhesion molecule) The protein encoded by this gene is an axonal glycoprotein belonging to the immunoglobulin supergene family. The ectodomain, consisting of several immunoglobulin-like domains and fibronectin-like repeats (type III), is linked via a single transmembrane sequence to a conserved cytoplasmic domain. This cell adhesion molecule plays an important role in nervous system development, including neuronal migration and differentiation. Mutations in the gene cause X-linked neurological syndromes known as CRASH (corpus callosum hypoplasia, retardation, aphasia, spastic paraplegia and hydrocephalus). Alternative splicing of this gene results in multiple transcript variants, some of which include an alternate exon that is considered to be specific to neurons. [provided by RefSeq, May 2013]

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: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
L1CAM	NM_001278116.2	c.1546G>A	p.Asp516Asn	missense_variant, splice_region_variant	13/29	ENST00000370060.7	NP_001265045.1
L1CAM	NM_000425.5	c.1546G>A	p.Asp516Asn	missense_variant, splice_region_variant	12/28		NP_000416.1
L1CAM	NM_024003.3	c.1546G>A	p.Asp516Asn	missense_variant, splice_region_variant	12/27		NP_076493.1
L1CAM	NM_001143963.2	c.1531G>A	p.Asp511Asn	missense_variant, splice_region_variant	11/26		NP_001137435.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
L1CAM	ENST00000370060.7	c.1546G>A	p.Asp516Asn	missense_variant, splice_region_variant	13/29	5	NM_001278116.2	ENSP00000359077	A1

Frequencies

GnomAD3 genomes Cov.: 24

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 24

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Spastic paraplegia Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Sep 16, 2018

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. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has been reported as hemizygous in individuals affected with L1 syndrome (PMID: 19846429). This variant is not present in population databases (ExAC no frequency). This sequence change replaces aspartic acid with asparagine at codon 516 of the L1CAM protein (p.Asp516Asn). The aspartic acid residue is weakly conserved and there is a small physicochemical difference between aspartic acid and asparagine. This variant also falls at the last nucleotide of exon 12 of the L1CAM coding sequence, which is part of the consensus splice site for this exon. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.16
BayesDel_addAF	Benign	-0.28	T
BayesDel_noAF	Benign	-0.64
CADD	Pathogenic	29
DANN	Benign	0.96
DEOGEN2	Uncertain	0.49	.;T;.;.
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.94	D;D;.;D
M_CAP	Pathogenic	0.37	D
MetaRNN	Benign	0.35	T;T;T;T
MetaSVM	Benign	-0.72	T
MutationAssessor	Benign	0.91	.;L;.;L
MutationTaster	Benign	0.99	D;D;D;D;D;D;D
PrimateAI	Benign	0.42	T
PROVEAN	Benign	-1.3	N;N;N;N
REVEL	Uncertain	0.31
Sift	Benign	0.50	T;T;T;T
Sift4G	Benign	0.47	T;T;T;T
Polyphen		0.011, 0.010	.;B;.;B
Vest4		0.24
MutPred		0.52		.;Gain of MoRF binding (P = 0.0385);.;Gain of MoRF binding (P = 0.0385);
MVP		0.73
MPC		0.53
ClinPred		0.37	T
GERP RS		5.6
Varity_R		0.25
gMVP		0.58

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.98
SpliceAI score (max)		0.84		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.84		Position offset: 7
DS_DL_spliceai		0.48		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: rs782367931; hg19: chrX-153134016;