17-8238504-C-T

Variant names:

• chr17-8238504-C-T
• rs368398609
• NM_025099.6:c.323G>A

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_025099.6(CTC1):​c.323G>A​(p.Arg108Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000657 in 152,300 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 31)
• Consequence: CTC1 NM_025099.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.616
• Publications: 2 publications found

Genes affected

CTC1 (HGNC:26169): (CST telomere replication complex component 1) This gene encodes a component of the CST complex. This complex plays an essential role in protecting telomeres from degradation. This protein also forms a heterodimer with the CST complex subunit STN1 to form the enzyme alpha accessory factor. This enzyme regulates DNA replication. Mutations in this gene are the cause of cerebroretinal microangiopathy with calcifications and cysts. Alternate splicing results in both coding and non-coding variants. [provided by RefSeq, Mar 2012]

CTC1 Gene-Disease associations (from GenCC):

• cerebroretinal microangiopathy with calcifications and cysts 1

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), PanelApp Australia, Ambry Genetics, G2P
• dyskeratosis congenita

  Inheritance: AR, AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: G2P, Orphanet
• Coats plus syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.21687475).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_025099.6. 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
	CTC1	NM_025099.6	MANE Select	c.323G>A	p.Arg108Gln	missense	Exon 3 of 23	NP_079375.3
	CTC1	NM_001411067.1		c.323G>A	p.Arg108Gln	missense	Exon 3 of 21	NP_001397996.1
	CTC1	NR_046431.2		n.343G>A		non_coding_transcript_exon	Exon 3 of 22

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CTC1	ENST00000651323.1	MANE Select	c.323G>A	p.Arg108Gln	missense	Exon 3 of 23	ENSP00000498499.1
	CTC1	ENST00000581729.2	TSL:3	c.323G>A	p.Arg108Gln	missense	Exon 3 of 21	ENSP00000462720.2
	CTC1	ENST00000580299.2	TSL:5	c.323G>A	p.Arg108Gln	missense	Exon 3 of 21	ENSP00000462607.2

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152180 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

GnomAD4 exome Cov.: 31

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152300 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 74462

African (AFR) AF: 0.0000241 AC: 1 AN: 41570

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

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3468

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

South Asian (SAS) AF: 0.00 AC: 0 AN: 4828

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

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 294

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68024

Other (OTH) AF: 0.00 AC: 0 AN: 2114

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000120 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Dyskeratosis congenita Uncertain:1

Aug 24, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine with glutamine at codon 108 of the CTC1 protein (p.Arg108Gln). The arginine residue is highly conserved and there is a small physicochemical difference between arginine and glutamine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with CTC1-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The glutamine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect 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.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.086
BayesDel_addAF	Benign	-0.021	T
BayesDel_noAF	Benign	-0.27
CADD	Benign	15
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.60	D
Eigen	Benign	-0.30
Eigen_PC	Benign	-0.29
FATHMM_MKL	Benign	0.45	N
LIST_S2	Benign	0.77	T
M_CAP	Benign	0.058	D
MetaRNN	Benign	0.22	T
MetaSVM	Uncertain	-0.19	T
MutationAssessor	Benign	1.9	L
PhyloP100		0.62
PrimateAI	Benign	0.24	T
PROVEAN	Benign	-1.6	N
REVEL	Uncertain	0.33
Sift	Benign	0.072	T
Sift4G	Pathogenic	0.0	D
Polyphen		0.27	B
Vest4		0.23
MVP		0.58
MPC		0.17
ClinPred		0.46	T
GERP RS		2.9
Varity_R		0.086
gMVP		0.59
Mutation Taster		=96/4	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs368398609; hg19: chr17-8141822; COSMIC: COSV59853486; COSMIC: COSV59853486;