rs1553795301

Positions:

• chr3-123682222-ACT-A

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PVS1_Moderate PM2 PP3_Moderate PP5_Moderate

The NM_053025.4(MYLK):​c.3652_3652+1del variant causes a splice donor, coding sequence change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000692 in 1,444,294 control chromosomes in the GnomAD database, with no homozygous occurrence. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★). Synonymous variant affecting the same amino acid position (i.e. S1218S) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: MYLK NM_053025.4 splice_donor, coding_sequence
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 3.33

Genes affected

MYLK (HGNC:7590): (myosin light chain kinase) This gene, a muscle member of the immunoglobulin gene superfamily, encodes myosin light chain kinase which is a calcium/calmodulin dependent enzyme. This kinase phosphorylates myosin regulatory light chains to facilitate myosin interaction with actin filaments to produce contractile activity. This gene encodes both smooth muscle and nonmuscle isoforms. In addition, using a separate promoter in an intron in the 3' region, it encodes telokin, a small protein identical in sequence to the C-terminus of myosin light chain kinase, that is independently expressed in smooth muscle and functions to stabilize unphosphorylated myosin filaments. A pseudogene is located on the p arm of chromosome 3. Four transcript variants that produce four isoforms of the calcium/calmodulin dependent enzyme have been identified as well as two transcripts that produce two isoforms of telokin. Additional variants have been identified but lack full length transcripts. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PVS1: Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 0.014969539 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6.5, offset of 0 (no position change), new splice context is: tgaGTgagt. 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
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 3-123682222-ACT-A is Pathogenic according to our data. Variant chr3-123682222-ACT-A is described in ClinVar as [Pathogenic]. Clinvar id is 471724.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MYLK	NM_053025.4	c.3652_3652+1del		splice_donor_variant, coding_sequence_variant	20/34	ENST00000360304.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MYLK	ENST00000360304.8	c.3652_3652+1del		splice_donor_variant, coding_sequence_variant	20/34	5	NM_053025.4	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.92e-7 AC: 1 AN: 1444294 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 716330

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: 9.06e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Aortic aneurysm, familial thoracic 7 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jun 06, 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. This variant is also known as c.3652_3652+1del. This premature translational stop signal has been observed in individual(s) with aortic dissection (Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (Splice site) in the MYLK gene. This variant occurs within the aortic-specific isoform of MYLK. Loss-of-function variants in the aortic-specific isoform of MYLK are known to be pathogenic for thoracic aortic dissections (PMID: 21055718). -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.99		Position offset: 4
DS_DL_spliceai		0.99		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: rs1553795301; hg19: chr3-123401069;