rs1554297727

Positions:

• chr6-129441000-T-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_Moderate PM2 PP5_Moderate

The NM_000426.4(LAMA2):​c.6268+2T>C variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: LAMA2 NM_000426.4 splice_donor, intron
• Scores: Splicing: ADA: 0.9998
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 7.33

Genes affected

LAMA2 (HGNC:6482): (laminin subunit alpha 2) Laminin, an extracellular protein, is a major component of the basement membrane. It is thought to mediate the attachment, migration, and organization of cells into tissues during embryonic development by interacting with other extracellular matrix components. It is composed of three subunits, alpha, beta, and gamma, which are bound to each other by disulfide bonds into a cross-shaped molecule. This gene encodes the alpha 2 chain, which constitutes one of the subunits of laminin 2 (merosin) and laminin 4 (s-merosin). Mutations in this gene have been identified as the cause of congenital merosin-deficient muscular dystrophy. Two transcript variants encoding different proteins have been found for this gene. [provided by RefSeq, Jul 2008]

ENSG00000226149 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.019425767 fraction of the gene. No cryptic splice site detected. Exon removal is inframe change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 6-129441000-T-C is Pathogenic according to our data. Variant chr6-129441000-T-C is described in ClinVar as [Pathogenic]. Clinvar id is 477498.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr6-129441000-T-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
LAMA2	NM_000426.4	c.6268+2T>C		splice_donor_variant, intron_variant		ENST00000421865.3	NP_000417.3
LAMA2	NM_001079823.2	c.6268+2T>C		splice_donor_variant, intron_variant			NP_001073291.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
LAMA2	ENST00000421865.3	c.6268+2T>C		splice_donor_variant, intron_variant		5	NM_000426.4	ENSP00000400365.2
LAMA2	ENST00000618192.5	c.6532+2T>C		splice_donor_variant, intron_variant		5		ENSP00000480802.2
LAMA2	ENST00000617695.5	c.6268+2T>C		splice_donor_variant, intron_variant		5		ENSP00000481744.2
ENSG00000226149	ENST00000665046.1	n.1228A>G		non_coding_transcript_exon_variant	10/10

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Inborn genetic diseases Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 29, 2024

The c.6268+2T>C intronic alteration consists of a T to C substitution two nucleotides after exon 43 of the LAMA2 gene. Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This alteration was detected in the compound heterozygous state, with another alteration in LAMA2, in an individual with LAMA2-related muscular dystrophy (Xiong, 2015). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Based on the available evidence, this alteration is classified as likely pathogenic. -

LAMA2-related muscular dystrophy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

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 disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 477498). Disruption of this splice site has been observed in individuals with congenital muscular dystrophy (PMID: 24611677; Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change affects a donor splice site in intron 43 of the LAMA2 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 LAMA2 are known to be pathogenic (PMID: 18700894, 32904964). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Uncertain	0.040
CADD	Pathogenic	27
DANN	Uncertain	0.99
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.87
FATHMM_MKL	Uncertain	0.92	D
GERP RS		5.5

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.86
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_DL_spliceai		1.0		Position offset: -2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1554297727; hg19: chr6-129762145;