rs121908245

Variant names:

• chr19-13332911-C-T
• rs121908245
• NM_001127222.2:c.1213G>A

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 1P and 0B. PP3

The NM_001127222.2(CACNA1A):​c.1213G>A​(p.Ala405Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000992 in 1,612,292 control chromosomes in the GnomAD database, with no homozygous occurrence. There is a variant allele frequency bias in the population database for this variant (GnomAdExome4), which may indicate mosaicism or somatic mutations in the reference population data. 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. A405V) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 31)
  • Exomes 𝑓: 0.000010 (0 hom.)
• Consequence: CACNA1A NM_001127222.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3 O:1
• Conservation: PhyloP100: 7.26
• Publications: 7 publications found

Genes affected

CACNA1A (HGNC:1388): (calcium voltage-gated channel subunit alpha1 A) Voltage-dependent calcium channels mediate the entry of calcium ions into excitable cells, and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, and gene expression. Calcium channels are multisubunit complexes composed of alpha-1, beta, alpha-2/delta, and gamma subunits. The channel activity is directed by the pore-forming alpha-1 subunit, whereas, the others act as auxiliary subunits regulating this activity. The distinctive properties of the calcium channel types are related primarily to the expression of a variety of alpha-1 isoforms, alpha-1A, B, C, D, E, and S. This gene encodes the alpha-1A subunit, which is predominantly expressed in neuronal tissue. Mutations in this gene are associated with 2 neurologic disorders, familial hemiplegic migraine and episodic ataxia 2. This gene also exhibits polymorphic variation due to (CAG)n-repeats. Multiple transcript variants encoding different isoforms have been found for this gene. In one set of transcript variants, the (CAG)n-repeats occur in the 3' UTR, and are not associated with any disease. But in another set of variants, an insertion extends the coding region to include the (CAG)n-repeats which encode a polyglutamine tract. Expansion of the (CAG)n-repeats from the normal 4-18 to 21-33 in the coding region is associated with spinocerebellar ataxia 6. [provided by RefSeq, Jul 2016]

CACNA1A Gene-Disease associations (from GenCC):

• episodic ataxia type 2

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Ambry Genetics, Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
• undetermined early-onset epileptic encephalopathy

  Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: Orphanet, Illumina
• developmental and epileptic encephalopathy, 42

  Inheritance: AD Classification: STRONG, MODERATE Submitted by: G2P, Ambry Genetics, Labcorp Genetics (formerly Invitae)
• migraine, familial hemiplegic, 1

  Inheritance: AD Classification: STRONG Submitted by: Ambry Genetics, Genomics England PanelApp, Labcorp Genetics (formerly Invitae)
• spinocerebellar ataxia type 6

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Orphanet
• benign paroxysmal torticollis of infancy

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• familial or sporadic hemiplegic migraine

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Lennox-Gastaut syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

• PP3: MetaRNN computational evidence supports a deleterious effect, 0.815

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001127222.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CACNA1A	NM_001127222.2	MANE Select	c.1213G>A	p.Ala405Thr	missense	Exon 9 of 47	NP_001120694.1
	CACNA1A	NM_001127221.2	MANE Plus Clinical	c.1213G>A	p.Ala405Thr	missense	Exon 9 of 47	NP_001120693.1
	CACNA1A	NM_023035.3		c.1213G>A	p.Ala405Thr	missense	Exon 9 of 48	NP_075461.2

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CACNA1A	ENST00000360228.11	TSL:1 MANE Select	c.1213G>A	p.Ala405Thr	missense	Exon 9 of 47	ENSP00000353362.5
	CACNA1A	ENST00000638009.2	TSL:1 MANE Plus Clinical	c.1213G>A	p.Ala405Thr	missense	Exon 9 of 47	ENSP00000489913.1
	CACNA1A	ENST00000638029.1	TSL:5	c.1213G>A	p.Ala405Thr	missense	Exon 9 of 48	ENSP00000489829.1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152112 Hom.: 0 Cov.: 31

Gnomad AFR AF: 0.0000241

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: 0.00

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000807 AC: 2 AN: 247982 AF XY: 0.00000743

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000103 AC: 15 AN: 1460180 Hom.: 0 Cov.: 29 AF XY: 0.0000124 AC XY: 9 AN XY: 726458

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000299 AC: 1 AN: 33464

American (AMR) AF: 0.00 AC: 0 AN: 44710

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26122

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86198

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53034

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5762

European-Non Finnish (NFE) AF: 0.0000108 AC: 12 AN: 1110874

Other (OTH) AF: 0.0000166 AC: 1 AN: 60320

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000918677), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152112 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 74298

African (AFR) AF: 0.0000241 AC: 1 AN: 41426

American (AMR) AF: 0.00 AC: 0 AN: 15266

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5178

South Asian (SAS) AF: 0.00 AC: 0 AN: 4830

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10610

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68018

Other (OTH) AF: 0.00 AC: 0 AN: 2086

Alfa AF: 0.0000201 Hom.: 0

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Episodic ataxia type 2;C4310716:Developmental and epileptic encephalopathy, 42 Uncertain:1

Aug 23, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 405 of the CACNA1A protein (p.Ala405Thr). This missense change has been observed in individual(s) with familial hemiplegic migraine and/or progressive spinocerebellar ataxia (PMID: 20682717). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 68419). 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 not expected to disrupt CACNA1A protein function. 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.

not provided Uncertain:1

May 19, 2022

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Reported previously in three affected females from a family with a spectrum of phenotypes including episodic ataxia, progressive spinocerebellar ataxia, and familial hemiplegic migraine; two male carriers in this family were reported to be unaffected, suggesting additional genetic and environmental factors may affect the clinical presentation (Romaniello et al., 2010); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 24486772, 27871455, 20682717, 32116539)

Developmental and epileptic encephalopathy, 42 Uncertain:1

Feb 02, 2022

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as VUS-3B. Following criteria are met: 0103 - Loss of function and gain of function are known mechanisms of disease in this gene. Type 2 episodic ataxia (MIM#108500) is mostly associated with loss of function, while familial hemiplegic migraine 1, with or without progressive cerebellar ataxia (MIM#141500) is associated with gain of function. Developmental and epileptic encephalopathy 42 (MIM#617106) is associated with both mechanisms, and spinocerebellar ataxia 6 (MIM#183086) is associated with CAG repeat expansion. (OMIM, PMIDs: 25735478, 28566750, 31468518, 32116539). (I) 0107 - This gene is associated with autosomal dominant disease. (I) 0112 - The condition associated with this gene has incomplete penetrance. Asymptomatic family members have been reported to carry the same variant as the affected family members (PMIDs: 10408533, 30142438). (I) 0115 - Variants in this gene are known to have variable expressivity. Intrafamilial variability has been reported for episodic ataxia, intellectual disability and/or epilepsy (PMIDs: 30142438, 32910250). (I) 0200 - Variant is predicted to result in a missense amino acid change from alanine to threonine. (I) 0251 - This variant is heterozygous. (I) 0302 - Variant is present in gnomAD (v2) <0.001 for a dominant condition (2 heterozygotes, 0 homozygotes). (SP) 0309 - An alternative amino acid change at the same position has been observed in gnomAD (v3) (1 heterozygote, 0 homozygotes). (I) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0600 - Variant is located in the annotated intracellular loop between transmembrane domains DI and DII (PMID: 20682717). (I) 0705 - No comparable missense variants have previous evidence for pathogenicity. (I) 0808 - Previous reports of pathogenicity for this variant are conflicting. It has been reported in a family in three affected members showing a spectrum of phenotypes including progressive spinocerebellar ataxia 6, episodic ataxia type 2 and familial hemiplegic migraine, and two unaffected members (PMID: 20682717). It has also been reported as a VUS once in ClinVar. (I) 1007 - No published functional evidence has been identified for this variant. (I) 1206 - This variant has been shown to be paternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign

Episodic ataxia type 2 Other:1

UniProtKB/Swiss-Prot

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.65
BayesDel_addAF	Pathogenic	0.33	D
BayesDel_noAF	Pathogenic	0.23
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.72	D
Eigen	Pathogenic	0.72
Eigen_PC	Pathogenic	0.71
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D
M_CAP	Uncertain	0.16	D
MetaRNN	Pathogenic	0.82	D
MetaSVM	Uncertain	0.25	D
MutationAssessor	Uncertain	2.4	M
PhyloP100		7.3
PrimateAI	Pathogenic	0.80	T
PROVEAN	Uncertain	-3.5	D
REVEL	Uncertain	0.62
Sift	Uncertain	0.0020	D
Sift4G	Uncertain	0.052	T
Polyphen		1.0	D
Vest4		0.85
MutPred		0.31		Gain of phosphorylation at A405 (P = 0.0076)
MVP		0.94
MPC		2.2
ClinPred		0.99	D
GERP RS		5.3
Varity_R		0.32
gMVP		0.59
Mutation Taster		=24/76	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
Splicevardb		2.0
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: rs121908245; hg19: chr19-13443725; COSMIC: COSV64189902; COSMIC: COSV64189902;