chr1-229432333-G-A

Position:

• chr1-229432333-G-A

Variant summary

Our verdict is Pathogenic. Variant got 13 ACMG points: 13P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Moderate

The NM_001100.4(ACTA1):​c.553C>T​(p.Arg185Cys) 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. 12/20 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R185S) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 31)
• Consequence: ACTA1 NM_001100.4 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• 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]

ACMG classification

Verdict is Pathogenic. Variant got 13 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, 3 uncertain in NM_001100.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-229432333-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 420099.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), ACTA1. . Gene score misZ 4.5292 (greater than the threshold 3.09). Trascript score misZ 6.088 (greater than threshold 3.09). GenCC has associacion of gene with 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: MetaRNN computational evidence supports a deleterious effect, 0.991
• PP5: Variant 1-229432333-G-A is Pathogenic according to our data. Variant chr1-229432333-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 464125.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr1-229432333-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ACTA1	NM_001100.4	c.553C>T	p.Arg185Cys	missense_variant	4/7	ENST00000366684.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ACTA1	ENST00000366684.7	c.553C>T	p.Arg185Cys	missense_variant	4/7	1	NM_001100.4	P1
ACTA1	ENST00000366683.4	c.553C>T	p.Arg185Cys	missense_variant	4/7	5
ACTA1	ENST00000684723.1	c.418C>T	p.Arg140Cys	missense_variant	3/6

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Actin accumulation myopathy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 19, 2022

Experimental studies have shown that this missense change does not substantially affect ACTA1 function (PMID: 15226407). For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Arg185 amino acid residue in ACTA1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 11333380, 12921789, 15198992, 15226407, 25470062). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt ACTA1 protein function. ClinVar contains an entry for this variant (Variation ID: 464125). This variant is also known as p.Arg183Cys. This missense change has been observed in individuals with severe nemaline myopathy (PMID: 10508519, 15226407, 24313005). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 185 of the ACTA1 protein (p.Arg185Cys). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.54	D
BayesDel_noAF	Pathogenic	0.54
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.97	D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.87
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Pathogenic	0.97	D
M_CAP	Pathogenic	0.74	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.2	H
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Pathogenic	0.90	D
PROVEAN	Pathogenic	-6.4	D
REVEL	Pathogenic	0.96
Sift4G	Uncertain	0.0090	D
Polyphen		1.0	D
Vest4		0.79
MutPred		0.95		Loss of phosphorylation at T188 (P = 0.0813);
MVP		0.99
ClinPred		1.0	D
GERP RS		4.6
Varity_R		0.97
gMVP		0.98

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

Publications

LitVar

Other links and lift over

dbSNP: rs1064794287; hg19: chr1-229568080;