rs1555420652

Positions:

• chr15-42389050-T-C

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP3_Strong PP5

The NM_000070.3(CAPN3):​c.755T>C​(p.Met252Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,882 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M252V) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: CAPN3 NM_000070.3 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:3
• Conservation: PhyloP100: 7.94

Genes affected

CAPN3 (HGNC:1480): (calpain 3) Calpain, a heterodimer consisting of a large and a small subunit, is a major intracellular protease, although its function has not been well established. This gene encodes a muscle-specific member of the calpain large subunit family that specifically binds to titin. Mutations in this gene are associated with limb-girdle muscular dystrophies type 2A. Alternate promoters and alternative splicing result in multiple transcript variants encoding different isoforms and some variants are ubiquitously expressed. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 11 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 7 uncertain in NM_000070.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-42389049-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 1507710.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.98
• PP5: Variant 15-42389050-T-C is Pathogenic according to our data. Variant chr15-42389050-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 555359.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=3, Pathogenic=1, Likely_pathogenic=1}. Variant chr15-42389050-T-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CAPN3	NM_000070.3	c.755T>C	p.Met252Thr	missense_variant	5/24	ENST00000397163.8
CAPN3	NM_024344.2	c.755T>C	p.Met252Thr	missense_variant	5/23
CAPN3	NM_173087.2	c.755T>C	p.Met252Thr	missense_variant	5/21

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CAPN3	ENST00000397163.8	c.755T>C	p.Met252Thr	missense_variant	5/24	1	NM_000070.3	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000795 AC: 2 AN: 251418 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135870

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

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: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461882 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 727246

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000447

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: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Autosomal recessive limb-girdle muscular dystrophy type 2A Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Dec 01, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Dec 02, 2023	This sequence change replaces methionine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 252 of the CAPN3 protein (p.Met252Thr). This variant is present in population databases (no rsID available, gnomAD 0.003%). This missense change has been observed in individual(s) with autosomal recessive CAPN3-related conditions (PMID: 18854869; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. This variant has been reported in individual(s) with autosomal dominant limb-girdle muscular dystrophy (PMID: 16141003); however, the role of the variant in this condition is currently unclear. ClinVar contains an entry for this variant (Variation ID: 555359). 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 expected to disrupt CAPN3 protein function with a positive predictive value of 80%. This variant disrupts the p.Met252 amino acid residue in CAPN3. Other variant(s) that disrupt this residue have been determined to be pathogenic (Invitae). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

not provided Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Oct 01, 2023	Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Identified with a second variant in an individual with limb girdle muscular dystrophy, but it is not known whether the variants occurred on the same (in cis) or on different (in trans) chromosomes (Fanin et al., 2009); Identified in an individual with limb girdle muscular dystrophy, but it is unknown whether this individual was tested for variants in other genes associated with muscular dystrophy (Piluso et al., 2005); This variant is associated with the following publications: (PMID: 18854869, 20635405, 16141003) -
Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 18, 2022	- -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Jul 20, 2021

Variant summary: CAPN3 c.755T>C (p.Met252Thr) results in a non-conservative amino acid change located in the Peptidase C2, calpain, catalytic domain (IPR001300) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 8e-06 in 251418 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.755T>C has been reported in the literature in at-least one comprehensively evaluated individual affected with Limb-Girdle Muscular Dystrophy (LGMD), Autosomal Recessive, who was compound heterozygous for this variant and c.1524+1G>C and whose muscle biopsy demonstrated 5% calpain quantity (Fanin_2009). This patient has been subsequently reported by others (example, Piluso_2005, Nascimbeni_2010). These data do not allow any conclusion about variant significance. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Two 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 uncertain significance citing overlapping evidence utilized in the context of this evaluation. Of note, two other variants at the same codon, namely, p.M252R and p.M252K have also been reported in other patients with LGMD supporting the functional importance of this residue. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.94
BayesDel_addAF	Pathogenic	0.38	D
BayesDel_noAF	Pathogenic	0.38
CADD	Pathogenic	26
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.49	T;.;.;D
Eigen	Uncertain	0.65
Eigen_PC	Uncertain	0.66
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.95	D;D;D;D
M_CAP	Uncertain	0.25	D
MetaRNN	Pathogenic	0.98	D;D;D;D
MetaSVM	Uncertain	0.68	D
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Uncertain	0.73	T
PROVEAN	Uncertain	-3.8	D;D;D;D
REVEL	Pathogenic	0.91
Sift	Uncertain	0.0020	D;D;D;D
Sift4G	Uncertain	0.0060	D;D;D;D
Polyphen		0.73, 0.38, 0.98	.;P;B;D
Vest4		0.92
MutPred		0.93		Loss of stability (P = 0.027);Loss of stability (P = 0.027);Loss of stability (P = 0.027);Loss of stability (P = 0.027);
MVP		0.97
MPC		0.63
ClinPred		0.97	D
GERP RS		5.4
Varity_R		0.94
gMVP		0.90

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs1555420652; hg19: chr15-42681248;