2-174749951-G-C

Variant names:

• chr2-174749951-G-C
• rs374391312
• NM_000079.4:c.997C>G

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM2 PM5 PP2 PP3_Moderate

The NM_000079.4(CHRNA1):​c.997C>G​(p.Arg333Gly) variant causes a missense change. 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R333W) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: CHRNA1 NM_000079.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.13
• Publications: 4 publications found

Genes affected

CHRNA1 (HGNC:1955): (cholinergic receptor nicotinic alpha 1 subunit) The muscle acetylcholine receptor consiststs of 5 subunits of 4 different types: 2 alpha subunits and 1 each of the beta, gamma, and delta subunits. This gene encodes an alpha subunit that plays a role in acetlycholine binding/channel gating. Alternatively spliced transcript variants encoding different isoforms have been identified. [provided by RefSeq, Nov 2012]

CHRNA1 Gene-Disease associations (from GenCC):

• congenital myasthenic syndrome 1A

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), PanelApp Australia
• lethal multiple pterygium syndrome

  Inheritance: AR Classification: STRONG, SUPPORTIVE, LIMITED Submitted by: Labcorp Genetics (formerly Invitae), Orphanet, G2P
• myasthenic syndrome, congenital, 1B, fast-channel

  Inheritance: AR, AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, PanelApp Australia
• postsynaptic congenital myasthenic syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ENSG00000236449 (HGNC:):

ACMG classification

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr2-174749951-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 29582.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 16 curated pathogenic missense variants (we use a threshold of 10). The gene has 5 curated benign missense variants. Gene score misZ: 0.72157 (below the threshold of 3.09). Trascript score misZ: 1.6771 (below the threshold of 3.09). GenCC associations: The gene is linked to lethal multiple pterygium syndrome, congenital myasthenic syndrome 1A, myasthenic syndrome, congenital, 1B, fast-channel, postsynaptic congenital myasthenic syndrome.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.928

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000079.4. 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
	CHRNA1	NM_000079.4	MANE Select	c.997C>G	p.Arg333Gly	missense	Exon 7 of 9	NP_000070.1
	CHRNA1	NM_001039523.3		c.1072C>G	p.Arg358Gly	missense	Exon 8 of 10	NP_001034612.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CHRNA1	ENST00000348749.9	TSL:1 MANE Select	c.997C>G	p.Arg333Gly	missense	Exon 7 of 9	ENSP00000261008.5
	ENSG00000236449	ENST00000442996.1	TSL:1	n.321+20127G>C		intron	N/A
	CHRNA1	ENST00000261007.9	TSL:2	c.1072C>G	p.Arg358Gly	missense	Exon 8 of 10	ENSP00000261007.5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Lethal multiple pterygium syndrome Uncertain:1

Oct 05, 2018

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with CHRNA1-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces arginine with glycine at codon 333 of the CHRNA1 protein (p.Arg333Gly). The arginine residue is highly conserved and there is a moderate physicochemical difference between arginine and glycine. 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.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.75
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.39
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.92	D
Eigen	Pathogenic	0.76
Eigen_PC	Uncertain	0.66
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.97	D
M_CAP	Pathogenic	0.43	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Pathogenic	0.82	D
MutationAssessor	Pathogenic	3.3	M
PhyloP100		5.1
PrimateAI	Uncertain	0.67	T
PROVEAN	Pathogenic	-5.5	D
REVEL	Pathogenic	0.91
Sift	Uncertain	0.0010	D
Sift4G	Pathogenic	0.0010	D
Polyphen		0.99	D
Vest4		0.95
MVP		0.93
MPC		1.0
ClinPred		1.0	D
GERP RS		3.6
Varity_R		0.94
gMVP		0.95
Mutation Taster		=7/93	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: rs374391312; hg19: chr2-175614679;