9-131052965-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_006059.4(LAMC3):c.1939G>T(p.Gly647Cys) variant causes a missense, splice region change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000156 in 1,607,172 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predicting alterations to normal splicing. 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. G647R) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000015 (0 hom.)
• Consequence: LAMC3 NM_006059.4 missense, splice_region
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.66

Genes affected

LAMC3 (HGNC:6494): (laminin subunit gamma 3) Laminins, a family of extracellular matrix glycoproteins, are the major noncollagenous constituent of basement membranes. They have been implicated in a wide variety of biological processes including cell adhesion, differentiation, migration, signaling, neurite outgrowth and metastasis. Laminins are composed of 3 non identical chains: laminin alpha, beta and gamma (formerly A, B1, and B2, respectively) and they form a cruciform structure consisting of 3 short arms, each formed by a different chain, and a long arm composed of all 3 chains. Each laminin chain is a multidomain protein encoded by a distinct gene. Several isoforms of each chain have been described. Different alpha, beta and gamma chain isomers combine to give rise to different heterotrimeric laminin isoforms which are designated by Arabic numerals in the order of their discovery, i.e. alpha1beta1gamma1 heterotrimer is laminin 1. The biological functions of the different chains and trimer molecules are largely unknown, but some of the chains have been shown to differ with respect to their tissue distribution, presumably reflecting diverse functions in vivo. This gene encodes the gamma chain isoform laminin, gamma 3. The gamma 3 chain is most similar to the gamma 1 chain, and contains all the 6 domains expected of the gamma chain. It is a component of laminin 12. The gamma 3 chain is broadly expressed in skin, heart, lung, and the reproductive tracts. In skin, it is seen within the basement membrane of the dermal-epidermal junction at points of nerve penetration. Gamma 3 is also a prominent element of the apical surface of ciliated epithelial cells of lung, oviduct, epididymis, ductus deferens, and seminiferous tubules. The distribution of gamma 3-containing laminins along ciliated epithelial surfaces suggests that the apical laminins are important in the morphogenesis and structural stability of the ciliated processes of these cells. [provided by RefSeq, Aug 2011]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 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	UniProt
LAMC3	NM_006059.4	c.1939G>T	p.Gly647Cys	missense_variant, splice_region_variant	11/28	ENST00000361069.9
LAMC3	XM_011518121.2	c.1939G>T	p.Gly647Cys	missense_variant, splice_region_variant	11/28
LAMC3	XM_006716921.3	c.1939G>T	p.Gly647Cys	missense_variant, splice_region_variant	11/23

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
LAMC3	ENST00000361069.9	c.1939G>T	p.Gly647Cys	missense_variant, splice_region_variant	11/28	2	NM_006059.4	P1

Frequencies

GnomAD3 genomes AF: 0.0000197 AC: 3 AN: 152262 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000294

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.00000817 AC: 2 AN: 244742 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 133088

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000182

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000151 AC: 22 AN: 1454910 Hom.: 0 Cov.: 32 AF XY: 0.0000193 AC XY: 14 AN XY: 724222

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: 0.0000172

Gnomad4 OTH exome AF: 0.0000499

GnomAD4 genome AF: 0.0000197 AC: 3 AN: 152262 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74390

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000294

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000113

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 21, 2023

This sequence change affects codon 647 of the LAMC3 mRNA. It is a 'silent' change, meaning that it does not change the encoded amino acid sequence of the LAMC3 protein. This variant also falls at the last nucleotide of exon 11, which is part of the consensus splice site for this exon. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This variant has not been reported in the literature in individuals affected with LAMC3-related conditions. An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. Variants that disrupt 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. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.27
BayesDel_addAF	Uncertain	0.098	D
BayesDel_noAF	Uncertain	0.010
Cadd	Pathogenic	35
Dann	Uncertain	1.0
DEOGEN2	Benign	0.17	T
Eigen	Uncertain	0.66
Eigen_PC	Uncertain	0.56
FATHMM_MKL	Uncertain	0.84	D
LIST_S2	Benign	0.44	T
M_CAP	Benign	0.035	D
MetaRNN	Uncertain	0.62	D
MetaSVM	Benign	-0.58	T
MutationAssessor	Pathogenic	3.1	M
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.51	T
PROVEAN	Pathogenic	-7.5	D
REVEL	Benign	0.29
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0050	D
Polyphen		1.0	D
Vest4		0.38
MutPred		0.62		Loss of glycosylation at S644 (P = 0.0709);
MVP		0.73
MPC		0.42
ClinPred		0.96	D
GERP RS		4.8
Varity_R		0.66
gMVP		0.69

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.99
SpliceAI score (max)		0.62		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.62		Position offset: 44
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: rs144242690; hg19: chr9-133928352;