1-201058407-C-T

Variant names:

• chr1-201058407-C-T
• rs754831666
• NM_000069.3:c.3609+1G>A

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PVS1_Moderate

The NM_000069.3(CACNA1S):​c.3609+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000062 in 1,613,466 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000055 (0 hom.)
• Consequence: CACNA1S NM_000069.3 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.88
• Publications: 0 publications found

Genes affected

CACNA1S (HGNC:1397): (calcium voltage-gated channel subunit alpha1 S) This gene encodes one of the five subunits of the slowly inactivating L-type voltage-dependent calcium channel in skeletal muscle cells. Mutations in this gene have been associated with hypokalemic periodic paralysis, thyrotoxic periodic paralysis and malignant hyperthermia susceptibility. [provided by RefSeq, Jul 2008]

CACNA1S Gene-Disease associations (from GenCC):

• congenital myopathy 18

  Inheritance: AD, AR Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• hypokalemic periodic paralysis, type 1

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, Ambry Genetics
• malignant hyperthermia, susceptibility to, 5

  Inheritance: AD Classification: STRONG, MODERATE Submitted by: ClinGen, Labcorp Genetics (formerly Invitae), Ambry Genetics
• congenital myopathy

  Inheritance: SD, AR, AD Classification: STRONG Submitted by: Illumina, Genomics England PanelApp
• hypokalemic periodic paralysis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.014941302 fraction of the gene. Cryptic splice site detected, with MaxEntScore 4.4, offset of 32, new splice context is: aggGTgggc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CACNA1S	NM_000069.3	c.3609+1G>A		splice_donor_variant, intron_variant	Intron 28 of 43	ENST00000362061.4	NP_000060.2
CACNA1S	XM_005245478.4	c.3609+1G>A		splice_donor_variant, intron_variant	Intron 28 of 42		XP_005245535.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CACNA1S	ENST00000362061.4	c.3609+1G>A		splice_donor_variant, intron_variant	Intron 28 of 43	1	NM_000069.3	ENSP00000355192.3

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152234 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000294

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000795 AC: 2 AN: 251472 AF XY: 0.00000736

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000547 AC: 8 AN: 1461232 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 726964

African (AFR) AF: 0.00 AC: 0 AN: 33462

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26132

East Asian (EAS) AF: 0.0000252 AC: 1 AN: 39700

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86240

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53416

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5764

European-Non Finnish (NFE) AF: 0.00000540 AC: 6 AN: 1111424

Other (OTH) AF: 0.00 AC: 0 AN: 60370

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152234 Hom.: 0 Cov.: 33 AF XY: 0.0000134 AC XY: 1 AN XY: 74372

African (AFR) AF: 0.00 AC: 0 AN: 41446

American (AMR) AF: 0.00 AC: 0 AN: 15294

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5194

South Asian (SAS) AF: 0.00 AC: 0 AN: 4838

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10618

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000294 AC: 2 AN: 68050

Other (OTH) AF: 0.00 AC: 0 AN: 2094

Alfa AF: 0.0000564 Hom.: 0

Bravo AF: 0.0000113

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Sep 08, 2023

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: CACNA1S c.3609+1G>A is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes a 5' splicing donor site. However, these predictions have yet to be confirmed by functional studies. Although a heterozygous loss-of-function variant has been reported in a patient affected with Hypokalaemic periodic paralysis (HOKPP; e.g., PMID 34777470), loss of function is not an established disease mechanism for HOKPP and Malignant Hyperthermia Susceptibility (MHS) (see e.g. PMID 33746731). The variant allele was found at a frequency of 2.1e-05 in 473476 control chromosomes (i.e., 10 heterozygotes; gnomAD and jMorp (Tadaka_2021) databases). The observed variant frequency is approximately 17 fold of the estimated maximal expected allele frequency for a pathogenic variant in CACNA1S causing Hypokalemic Periodic Paralysis phenotype (1.3e-06), suggesting that the variant may be benign. To our knowledge, no occurrence of c.3609+1G>A in individuals affected with Hypokalemic Periodic Paralysis and no experimental evidence demonstrating its impact on protein function have been reported. The following publication was ascertained in the context of this evaluation (PMID: 33179747). No submitters have reported clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.46	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	34
DANN	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.93
FATHMM_MKL	Pathogenic	0.99	D
PhyloP100		7.9
GERP RS		4.3
Mutation Taster		=1/99	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.99		Position offset: 1

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

Other links and lift over

dbSNP: rs754831666; hg19: chr1-201027535; COSMIC: COSV62937012;