rs878855127

Variant names:

• chr17-8230291-C-T
• rs878855127
• NM_025099.6:c.2933+3G>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.2933+3G>A variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000687 in 1,455,968 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: CTC1 NM_025099.6 splice_region, intron
• Scores: Splicing: ADA: 0.00008613
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.144
• Publications: 0 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 (BayesDel_noAF=-0.43).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CTC1	NM_025099.6	c.2933+3G>A		splice_region_variant, intron_variant	Intron 17 of 22	ENST00000651323.1	NP_079375.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CTC1	ENST00000651323.1	c.2933+3G>A		splice_region_variant, intron_variant	Intron 17 of 22		NM_025099.6	ENSP00000498499.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.87e-7 AC: 1 AN: 1455968 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 724192

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

African (AFR) AF: 0.00 AC: 0 AN: 33270

American (AMR) AF: 0.00 AC: 0 AN: 44136

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25634

East Asian (EAS) AF: 0.00 AC: 0 AN: 39690

South Asian (SAS) AF: 0.00 AC: 0 AN: 85388

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53218

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 4738

European-Non Finnish (NFE) AF: 9.01e-7 AC: 1 AN: 1109840

Other (OTH) AF: 0.00 AC: 0 AN: 60054

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Dyskeratosis congenita Uncertain:1

Oct 19, 2019

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant is not likely to affect RNA splicing, but this prediction has not been confirmed by published transcriptional studies. This variant has not been reported in the literature in individuals with CTC1-related conditions. ClinVar contains an entry for this variant (Variation ID: 241582). This variant is not present in population databases (ExAC no frequency). This sequence change falls in intron 17 of the CTC1 gene. It does not directly change the encoded amino acid sequence of the CTC1 protein, but it affects a nucleotide within the consensus splice site of the intron. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.43
CADD	Benign	9.9
DANN	Benign	0.72
PhyloP100		-0.14
PromoterAI		0.026	Neutral
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.000086
dbscSNV1_RF	Benign	0.054
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: rs878855127; hg19: chr17-8133609;