rs1553639782

Variant names:

• chr3-46858273-CT-C
• rs1553639782
• NM_000258.3:c.560-2delA

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PVS1_Moderate PM2

The NM_000258.3(MYL3):​c.560-2delA variant causes a splice acceptor, intron change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: MYL3 NM_000258.3 splice_acceptor, intron
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.63
• Publications: 0 publications found

Genes affected

MYL3 (HGNC:7584): (myosin light chain 3) MYL3 encodes myosin light chain 3, an alkali light chain also referred to in the literature as both the ventricular isoform and the slow skeletal muscle isoform. Mutations in MYL3 have been identified as a cause of mid-left ventricular chamber type hypertrophic cardiomyopathy. [provided by RefSeq, Jul 2008]

MYL3 Gene-Disease associations (from GenCC):

• hypertrophic cardiomyopathy

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• hypertrophic cardiomyopathy 8

  Inheritance: AD, SD Classification: DEFINITIVE, STRONG Submitted by: PanelApp Australia, G2P, Labcorp Genetics (formerly Invitae), Ambry Genetics
• arrhythmogenic right ventricular cardiomyopathy

  Inheritance: AD Classification: LIMITED Submitted by: ClinGen
• dilated cardiomyopathy

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

ACMG classification

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.071428575 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.8, offset of 42, new splice context is: cagctaaacctcgtgcccAGgta. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MYL3	NM_000258.3	c.560-2delA		splice_acceptor_variant, intron_variant	Intron 5 of 6	ENST00000292327.6	NP_000249.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MYL3	ENST00000292327.6	c.560-2delA		splice_acceptor_variant, intron_variant	Intron 5 of 6	1	NM_000258.3	ENSP00000292327.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hypertrophic cardiomyopathy Uncertain:1

Aug 03, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects an acceptor splice site in intron 5 of the MYL3 gene. It is expected to disrupt RNA splicing and likely results in an absent or disrupted protein product. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a MYL3-related disease. The current clinical and genetic evidence is not sufficient to establish whether loss-of-function variants in MYL3 cause disease. Therefore, this variant has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		7.6

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.86		Position offset: -12
DS_AL_spliceai		0.99		Position offset: -1

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

Other links and lift over

dbSNP: rs1553639782; hg19: chr3-46899763;