rs1553255360

Variant names:

• chr1-229431899-A-C
• rs1553255360
• NM_001100.4:c.812T>G

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP2 PP3_Moderate PP5_Moderate

The NM_001100.4(ACTA1):​c.812T>G​(p.Met271Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M271V) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: ACTA1 NM_001100.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 9.27

Genes affected

ACTA1 (HGNC:129): (actin alpha 1, skeletal muscle) The product encoded by this gene belongs to the actin family of proteins, which are highly conserved proteins that play a role in cell motility, structure and integrity. Alpha, beta and gamma actin isoforms have been identified, with alpha actins being a major constituent of the contractile apparatus, while beta and gamma actins are involved in the regulation of cell motility. This actin is an alpha actin that is found in skeletal muscle. Mutations in this gene cause a variety of myopathies, including nemaline myopathy, congenital myopathy with excess of thin myofilaments, congenital myopathy with cores, and congenital myopathy with fiber-type disproportion, diseases that lead to muscle fiber defects with manifestations such as hypotonia. [provided by RefSeq, Sep 2019]

ENSG00000290037 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_001100.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the ACTA1 gene, where missense mutations are typically associated with disease (based on misZ statistic). The gene has 154 curated pathogenic missense variants (we use a threshold of 10). The gene has 0 curated benign missense variants. Gene score misZ: 4.5292 (above the threshold of 3.09). Trascript score misZ: 6.088 (above the threshold of 3.09). GenCC associations: The gene is linked to congenital myopathy with excess of thin filaments, nemaline myopathy 3, intermediate nemaline myopathy, typical nemaline myopathy, congenital fiber-type disproportion myopathy, severe congenital nemaline myopathy, rigid spine syndrome, zebra body myopathy, childhood-onset nemaline myopathy, congenital myopathy 2c, severe infantile, autosomal dominant, alpha-actinopathy, progressive scapulohumeroperoneal distal myopathy.
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 1-229431899-A-C is Pathogenic according to our data. Variant chr1-229431899-A-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 464135.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr1-229431899-A-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ACTA1	NM_001100.4	c.812T>G	p.Met271Arg	missense_variant	Exon 6 of 7	ENST00000366684.7	NP_001091.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ACTA1	ENST00000366684.7	c.812T>G	p.Met271Arg	missense_variant	Exon 6 of 7	1	NM_001100.4	ENSP00000355645.3
ACTA1	ENST00000366683.4	c.812T>G	p.Met271Arg	missense_variant	Exon 6 of 7	5		ENSP00000355644.4
ACTA1	ENST00000684723.1	c.677T>G	p.Met226Arg	missense_variant	Exon 5 of 6			ENSP00000508084.1
ENSG00000290037	ENST00000702606.1	n.*60A>C		downstream_gene_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Actin accumulation myopathy Pathogenic:1

Jun 07, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces methionine with arginine at codon 271 of the ACTA1 protein (p.Met271Arg). The methionine residue is highly conserved and there is a moderate physicochemical difference between methionine and arginine. This variant is not present in population databases (ExAC no frequency). This variant has been reported in 3 individuals affected with nemaline myopathy and shown to arise de novo in 2 affected individuals (PMID: 11166164, 19562689, Invitae database). This variant is also known as M269R in the literature. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive, but these predictions have not been confirmed by published functional studies. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may alter RNA splicing, but this prediction has not been confirmed by published transcriptional studies. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.66
BayesDel_addAF	Pathogenic	0.45	D
BayesDel_noAF	Pathogenic	0.41
CADD	Pathogenic	35
DANN	Benign	0.93
DEOGEN2	Pathogenic	0.91	D
Eigen	Benign	-0.014
Eigen_PC	Benign	0.13
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	D
M_CAP	Pathogenic	0.76	D
MetaRNN	Pathogenic	0.94	D
MetaSVM	Uncertain	0.19	D
MutationAssessor	Benign	0.69	N
PrimateAI	Pathogenic	0.84	D
PROVEAN	Uncertain	-2.9	D
REVEL	Pathogenic	0.81
Sift4G	Benign	0.17	T
Polyphen		0.0	B
Vest4		0.93
MutPred		0.74		Gain of disorder (P = 0.0501);
MVP		0.98
ClinPred		0.98	D
GERP RS		4.5
Varity_R		0.99
gMVP		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.88		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.88		Position offset: -1

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

Publications

LitVar

Other links and lift over

dbSNP: rs1553255360; hg19: chr1-229567646;