1-229432813-A-C

Variant names:

• chr1-229432813-A-C
• rs1553255502
• NM_001100.4:c.197T>G

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Moderate

The NM_001100.4(ACTA1):​c.197T>G​(p.Ile66Ser) 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. I66N) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: ACTA1 NM_001100.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 9.32
• Publications: 0 publications found

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]

ACTA1 Gene-Disease associations (from GenCC):

• alpha-actinopathy

  Inheritance: AR, AD Classification: DEFINITIVE Submitted by: ClinGen
• congenital myopathy 2a, typical, autosomal dominant

  Inheritance: AR, SD, AD Classification: DEFINITIVE, STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae), Ambry Genetics
• congenital myopathy with excess of thin filaments

  Inheritance: SD Classification: DEFINITIVE Submitted by: Illumina
• congenital myopathy 2c, severe infantile, autosomal dominant

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• childhood-onset nemaline myopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• congenital fiber-type disproportion myopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• intermediate nemaline myopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• progressive scapulohumeroperoneal distal myopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• typical nemaline myopathy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• rigid spine syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• severe congenital nemaline myopathy

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• zebra body myopathy

  Inheritance: Unknown Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 11 ACMG points.

• PM1: In a hotspot region, there are 9 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 4 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 chr1-229432813-A-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 464119.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• 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, congenital fiber-type disproportion myopathy, severe congenital nemaline myopathy, congenital myopathy 2a, typical, autosomal dominant, zebra body myopathy, alpha-actinopathy, rigid spine syndrome, progressive scapulohumeroperoneal distal myopathy, childhood-onset nemaline myopathy, typical nemaline myopathy, intermediate nemaline myopathy, congenital myopathy 2c, severe infantile, autosomal dominant.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.93
• PP5: Variant 1-229432813-A-C is Pathogenic according to our data. Variant chr1-229432813-A-C is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 947145.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ACTA1	NM_001100.4	c.197T>G	p.Ile66Ser	missense_variant	Exon 3 of 7	ENST00000366684.7	NP_001091.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ACTA1	ENST00000366684.7	c.197T>G	p.Ile66Ser	missense_variant	Exon 3 of 7	1	NM_001100.4	ENSP00000355645.3
ACTA1	ENST00000366683.4	c.197T>G	p.Ile66Ser	missense_variant	Exon 3 of 7	5		ENSP00000355644.4
ACTA1	ENST00000684723.1	c.62T>G	p.Ile21Ser	missense_variant	Exon 2 of 6			ENSP00000508084.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 38

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 09, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. This variant disrupts the p.Ile66 amino acid residue in ACTA1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 12921789, 15226407, 15236405). 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: 947145). This missense change has been observed in individual(s) with ACTA1-related conditions (PMID: 19562689). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces isoleucine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 66 of the ACTA1 protein (p.Ile66Ser). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.45	D
BayesDel_noAF	Pathogenic	0.41
CADD	Pathogenic	31
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.92	D;D
Eigen	Pathogenic	0.80
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.93	D;D
M_CAP	Pathogenic	0.48	D
MetaRNN	Pathogenic	0.93	D;D
MetaSVM	Pathogenic	0.94	D
MutationAssessor	Uncertain	2.4	M;.
PhyloP100		9.3
PrimateAI	Pathogenic	0.90	D
PROVEAN	Uncertain	-3.3	D;N
REVEL	Pathogenic	0.91
Sift	Uncertain	0.0010	.;D
Sift4G	Uncertain	0.031	D;D
Polyphen		0.92	P;.
Vest4		0.94
MutPred		0.67		Gain of disorder (P = 0.0016);Gain of disorder (P = 0.0016);
MVP		0.99
ClinPred		0.99	D
GERP RS		4.7
Varity_R		0.98
gMVP		0.99
Mutation Taster		=0/100	disease causing

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: rs1553255502; hg19: chr1-229568560;