3-123700189-GCT-G

Variant names:

• chr3-123700189-GCT-G
• rs1553803217
• NM_053025.4:c.3277_3278delAG

Variant summary

Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_053025.4(MYLK):​c.3277_3278delAG​(p.Ser1093ProfsTer31) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Uncertain significance (★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 30)
• Consequence: MYLK NM_053025.4 frameshift
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.85
• Publications: 0 publications found

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]

MYLK-AS1 (HGNC:42440): (MYLK antisense RNA 1)

LOC105369194 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 10 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_053025.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	MYLK	NM_053025.4	MANE Select	c.3277_3278delAG	p.Ser1093ProfsTer31	frameshift	Exon 18 of 34	NP_444253.3
	MYLK	NM_053027.4		c.3277_3278delAG	p.Ser1093ProfsTer31	frameshift	Exon 18 of 33	NP_444255.3
	MYLK	NM_053026.4		c.3070_3071delAG	p.Ser1024ProfsTer31	frameshift	Exon 17 of 33	NP_444254.3

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	MYLK	ENST00000360304.8	TSL:5 MANE Select	c.3277_3278delAG	p.Ser1093ProfsTer31	frameshift	Exon 18 of 34	ENSP00000353452.3
	MYLK	ENST00000504946.6	TSL:1	c.886_887delAG	p.Ser296fs	frameshift	Exon 2 of 4	ENSP00000510315.1
	MYLK	ENST00000464489.5	TSL:1	n.*2856_*2857delAG		non_coding_transcript_exon	Exon 17 of 33	ENSP00000417798.1

Frequencies

GnomAD3 genomes Cov.: 30

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 30

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Familial thoracic aortic aneurysm and aortic dissection Uncertain:1

Apr 12, 2017

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.3277_3278delAG variant, located in coding exon 15 of the MYLK gene, results from a deletion of two nucleotides at nucleotide positions 3277 to 3278, causing a translational frameshift with a predicted alternate stop codon (p.S1093Pfs*31). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. Although loss of function alterations in MYLK have been associated with thoracic aortic aneurysms and dissections (TAAD) in two studies (Wang L et al. Am J Hum Genet. 2010;87(5):701-7; Hannuksela M et al. BMC Med Genet. 2016;17(1):61), loss of function of MYLK has not been clearly established as a mechanism of disease. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		1.9

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

Other links and lift over

dbSNP: rs1553803217; hg19: chr3-123419036;