1-229431562-C-G

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM1 PM2 PP2 PP3_Moderate

The NM_001100.4(ACTA1):c.1071G>C(p.Met357Ile) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,756 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 Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M357V) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: ACTA1 NM_001100.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 7.86

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]

(HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 7 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, 5 uncertain in NM_001100.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, ACTA1
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.903

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ACTA1	NM_001100.4	c.1071G>C	p.Met357Ile	missense_variant	7/7	ENST00000366684.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ACTA1	ENST00000366684.7	c.1071G>C	p.Met357Ile	missense_variant	7/7	1	NM_001100.4	P1
	ENST00000702606.1	n.197C>G		non_coding_transcript_exon_variant	1/1
ACTA1	ENST00000684723.1	c.936G>C	p.Met312Ile	missense_variant	6/6
ACTA1	ENST00000366683.4	c.993G>C	p.Met331Ile	missense_variant, splice_region_variant	7/7	5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461756 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727182

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: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Actin accumulation myopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Dec 23, 2019

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with ACTA1-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces methionine with isoleucine at codon 357 of the ACTA1 protein (p.Met357Ile). The methionine residue is highly conserved and there is a small physicochemical difference between methionine and isoleucine. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Apr 16, 2019

Not observed in large population cohorts (Lek et al., 2016); The majority of missense variants in this gene are considered pathogenic (Stenson et al., 2014); In silico analysis, which includes protein predictors and evolutionary conservation, supports that this variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.47	D
BayesDel_noAF	Pathogenic	0.43
Cadd	Pathogenic	28
Dann	Uncertain	0.99
DEOGEN2	Pathogenic	0.93	D;D
Eigen	Uncertain	0.49
Eigen_PC	Uncertain	0.48
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Benign	0.85	T;T
M_CAP	Pathogenic	0.55	D
MetaRNN	Pathogenic	0.90	D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.4	M;.
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.91	D
PROVEAN	Benign	-1.9	N;.
REVEL	Pathogenic	0.92
Sift4G	Uncertain	0.044	D;T
Polyphen		0.22	B;.
Vest4		0.79
MutPred		0.77		Loss of loop (P = 0.1242);.;
MVP		0.99
ClinPred		1.0	D
GERP RS		3.9
Varity_R		0.97
gMVP		0.98

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs745494410; hg19: chr1-229567309;