X-153866802-G-A

Position:

• chrX-153866802-G-A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_001278116.2(L1CAM):​c.2278C>T​(p.Arg760Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. R760R) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 23)
• Consequence: L1CAM NM_001278116.2 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 0.272

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 Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant X-153866802-G-A is Pathogenic according to our data. Variant chrX-153866802-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 211339.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chrX-153866802-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
L1CAM	NM_001278116.2	c.2278C>T	p.Arg760Ter	stop_gained	19/29	ENST00000370060.7
L1CAM	NM_000425.5	c.2278C>T	p.Arg760Ter	stop_gained	18/28
L1CAM	NM_024003.3	c.2278C>T	p.Arg760Ter	stop_gained	18/27
L1CAM	NM_001143963.2	c.2263C>T	p.Arg755Ter	stop_gained	17/26

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
L1CAM	ENST00000370060.7	c.2278C>T	p.Arg760Ter	stop_gained	19/29	5	NM_001278116.2	A1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 23

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jul 01, 2022	L1CAM: PVS1, PM2 -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Mar 15, 2021	Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss-of-function is a known mechanism of disease; Not observed in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 25525159, 19846429) -

L1 syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Dec 14, 2022

Variant summary: L1CAM c.2278C>T (p.Arg760X) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been associated with Hydrocephalus, X-linked in HGMD. The variant was absent in 182879 control chromosomes. c.2278C>T has been reported in the literature as a hemizygous genotype in individuals affected with Hydrocephaly, associated with L1 Syndrome(Example: Ganapathy_2019). To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

X-linked hydrocephalus syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Genomic Research Center, Shahid Beheshti University of Medical Sciences

Aug 07, 2018

- -

Hydrocephalus due to aqueductal stenosis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Genetic Services Laboratory, University of Chicago

Jun 05, 2015

- -

X-linked complicated corpus callosum dysgenesis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Genomic Research Center, Shahid Beheshti University of Medical Sciences

Aug 07, 2018

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.36	D
BayesDel_noAF	Pathogenic	0.28
CADD	Pathogenic	32
DANN	Uncertain	1.0
FATHMM_MKL	Benign	0.13	N
MutationTaster	Benign	1.0	A;A;A;A;A;A;A
Vest4		0.92
GERP RS		0.93
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs797045673; hg19: chrX-153132257;