chr17-7455781-ACTC-A

Variant names:

• chr17-7455781-ACTC-A
• rs781689096
• NM_000747.3:c.1218-9_1218-7delCTC

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PP5_Very_Strong

The NM_000747.3(CHRNB1):​c.1218-9_1218-7delCTC variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000223 in 1,613,606 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: 𝑓 0.000040 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000021 (0 hom.)
• Consequence: CHRNB1 NM_000747.3 splice_region, intron
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 1.13

Genes affected

CHRNB1 (HGNC:1961): (cholinergic receptor nicotinic beta 1 subunit) The muscle acetylcholine receptor is composed of five subunits: two alpha subunits and one beta, one gamma, and one delta subunit. This gene encodes the beta subunit of the acetylcholine receptor. The acetylcholine receptor changes conformation upon acetylcholine binding leading to the opening of an ion-conducting channel across the plasma membrane. Mutations in this gene are associated with slow-channel congenital myasthenic syndrome. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PP5: Variant 17-7455781-ACTC-A is Pathogenic according to our data. Variant chr17-7455781-ACTC-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 504421.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CHRNB1	NM_000747.3	c.1218-9_1218-7delCTC		splice_region_variant, intron_variant	Intron 9 of 10	ENST00000306071.7	NP_000738.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CHRNB1	ENST00000306071.7	c.1218-9_1218-7delCTC		splice_region_variant, intron_variant	Intron 9 of 10	1	NM_000747.3	ENSP00000304290.2

Frequencies

GnomAD3 genomes AF: 0.0000395 AC: 6 AN: 151730 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00115

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.000480

GnomAD3 exomes AF: 0.0000438 AC: 11 AN: 251248 Hom.: 0 AF XY: 0.0000368 AC XY: 5 AN XY: 135816

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.000893

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000881

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000205 AC: 30 AN: 1461876 Hom.: 0 AF XY: 0.0000151 AC XY: 11 AN XY: 727238

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.000574

Gnomad4 EAS exome AF: 0.0000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000809

Gnomad4 OTH exome AF: 0.0000662

GnomAD4 genome AF: 0.0000395 AC: 6 AN: 151730 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74092

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00115

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000147

Gnomad4 OTH AF: 0.000480

Alfa AF: 0.000130 Hom.: 0

Bravo AF: 0.0000378

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Congenital myasthenic syndrome 2A Pathogenic:1

Jan 15, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change falls in intron 9 of the CHRNB1 gene. It does not directly change the encoded amino acid sequence of the CHRNB1 protein. This variant is present in population databases (rs781689096, gnomAD 0.09%). This variant has been observed in individual(s) with clinical features of autosomal recessive congenital myasthenic syndrome (PMID: 33296147; internal data). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

not provided Pathogenic:1

Sep 18, 2018

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.1218-9_1218-7delCTC variant in the CHRNB1 gene has not been reported previously as a pathogenic variant nor as a benign variant, to our knowledge. This variant reduces the quality of the natural splice acceptor site in intron 9, and is expected to cause abnormal gene splicing. The c.1218-9_1218-7delCTC variant is not observed at a significant frequency in large population cohorts (Lek et al., 2016). We interpret c.1218-9_1218-7delCTC as a likely pathogenic variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
La Branchor		0.27
BranchPoint Hunter		1.0

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.34		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.25		Position offset: -2
DS_AL_spliceai		0.34		Position offset: 13

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

Publications

LitVar

Other links and lift over

dbSNP: rs781689096; hg19: chr17-7359100;