1-229432190-G-T

Variant names:

• chr1-229432190-G-T
• rs199804338
• NM_001100.4:c.617-5C>A

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PP1_Moderate PP3 PM2_Supporting PS4_Supporting

This summary comes from the ClinGen Evidence Repository: The c.617-5C>A variant in ACTA1 is an intronic variant in the 3’ non-canonical splice site of intron 4. This variant is predicted to create a cryptic splice site, and add one amino acid (Ala) translated from intron 4 to the mature protein, but the exact impact is unknown because no functional studies have been performed. This variant is absent from gnomAD v4.1.0 (PM2_Supporting). The computational predictor SpliceAI gives a score of 1 predicting an acceptor gain, which is above the threshold of 0.5, evidence that correlates with impact to ACTA1 function (PP3). This variant has been reported in two families with myopathy without muscle biopsies and three adults with features of muscle weakness (PS4_Supporting; PMID:19562689, Invitae, SCV001556001.2, GeneDx, SCV001986137.1). The variant has been reported to segregate with myopathy in 2 affected family members from 1 family (PP1_Moderate, Invitae, SCV001556001.2). In summary, this variant meets the criteria to be classified as uncertain significance for autosomal dominant alpha-actinopathy based on the ACMG/AMP criteria applied, as specified by the ClinGen Congenital Myopathies VCEP: PS4_Supporting, PP1_Moderate, PM2_Supporting, PP3 (Congenital Myopathies VCEP specifications version 2; 08/27/2024). LINK:https://erepo.genome.network/evrepo/ui/classification/CA2499214555/MONDO:0100084/147

• Frequency: Genomes: not found (cov: 31)
• Consequence: ACTA1 NM_001100.4 splice_region, intron
• Scores: Splicing: ADA: 0.9873
• Clinical Significance: Uncertain significance reviewed by expert panel P:1 U:3
• Conservation: PhyloP100: -0.521
• 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: AD, AR, SD 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
• hypertrophic cardiomyopathy

  Inheritance: AD Classification: NO_KNOWN Submitted by: ClinGen

ACMG classification

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

• PS4: For more information check the summary or visit ClinGen Evidence Repository.
• PM2: For more information check the summary or visit ClinGen Evidence Repository.
• PP1: For more information check the summary or visit ClinGen Evidence Repository.
• PP3: For more information check the summary or visit ClinGen Evidence Repository.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001100.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	ACTA1	NM_001100.4	MANE Select	c.617-5C>A		splice_region intron	N/A	NP_001091.1	P68133

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	ACTA1	ENST00000366684.7	TSL:1 MANE Select	c.617-5C>A		splice_region intron	N/A	ENSP00000355645.3	P68133
	ACTA1	ENST00000871224.1		c.617-5C>A		splice_region intron	N/A	ENSP00000541283.1
	ACTA1	ENST00000871225.1		c.617-5C>A		splice_region intron	N/A	ENSP00000541284.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 31

ClinVar

ClinVar submissions

Significance: Uncertain significance

Revision: reviewed by expert panel

Pathogenic	VUS	Benign	Condition
-	2	-	not provided (2)
1	-	-	Actin accumulation myopathy (1)
-	1	-	Alpha-actinopathy (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.84
CADD	Benign	22
DANN	Benign	0.48
PhyloP100		-0.52
Mutation Taster		=24/76	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	0.99
dbscSNV1_RF	Benign	0.67
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_AG_spliceai		1.0		Position offset: -2

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

Other links and lift over

dbSNP: rs199804338; hg19: chr1-229567937;