rs188259026

Positions:

• chr8-1771563-C-G
• chr8-1771563-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The ENST00000331222.6(CLN8):​c.509C>G​(p.Thr170Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,820 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. T170M) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: CLN8 ENST00000331222.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.36

Genes affected

CLN8 (HGNC:2079): (CLN8 transmembrane ER and ERGIC protein) This gene encodes a transmembrane protein belonging to a family of proteins containing TLC domains, which are postulated to function in lipid synthesis, transport, or sensing. The protein localizes to the endoplasmic reticulum (ER), and may recycle between the ER and ER-Golgi intermediate compartment. Mutations in this gene are associated with a disorder characterized by progressive epilepsy with cognitive disabilities (EPMR), which is a subtype of neuronal ceroid lipofuscinoses (NCL). Patients with mutations in this gene have altered levels of sphingolipid and phospholipids in the brain. [provided by RefSeq, Jul 2017]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a domain TLC (size 200) in uniprot entity CLN8_HUMAN there are 39 pathogenic changes around while only 14 benign (74%) in ENST00000331222.6
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.919

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CLN8	NM_018941.4	c.509C>G	p.Thr170Arg	missense_variant	2/3	ENST00000331222.6	NP_061764.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CLN8	ENST00000331222.6	c.509C>G	p.Thr170Arg	missense_variant	2/3	1	NM_018941.4	ENSP00000328182	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251224 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135830

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS 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: 6.84e-7 AC: 1 AN: 1461820 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727214

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Neuronal ceroid lipofuscinosis Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 23, 2022

This sequence change replaces threonine, which is neutral and polar, with arginine, which is basic and polar, at codon 170 of the CLN8 protein (p.Thr170Arg). 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. 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 expected to disrupt CLN8 protein function. This missense change has been observed in individual(s) with neuronal ceroid lipofuscinosis (PMID: 24767253). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.36	D
BayesDel_noAF	Pathogenic	0.37
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.95	D;D;D;D;.;D;.
Eigen	Pathogenic	0.71
Eigen_PC	Uncertain	0.66
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.91	.;.;.;.;D;.;D
M_CAP	Uncertain	0.20	D
MetaRNN	Pathogenic	0.92	D;D;D;D;D;D;D
MetaSVM	Uncertain	0.68	D
MutationAssessor	Uncertain	2.6	M;M;M;M;.;M;.
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.78	T
PROVEAN	Uncertain	-3.9	D;.;.;.;.;.;.
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0050	D;.;.;.;.;.;.
Sift4G	Pathogenic	0.0	D;.;.;.;.;.;D
Polyphen		1.0	D;D;D;D;.;D;.
Vest4		0.99
MutPred		0.78		Gain of solvent accessibility (P = 0.0171);Gain of solvent accessibility (P = 0.0171);Gain of solvent accessibility (P = 0.0171);Gain of solvent accessibility (P = 0.0171);Gain of solvent accessibility (P = 0.0171);Gain of solvent accessibility (P = 0.0171);Gain of solvent accessibility (P = 0.0171);
MVP		0.95
MPC		0.30
ClinPred		0.98	D
GERP RS		5.1
Varity_R		0.60
gMVP		0.98

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs188259026; hg19: chr8-1719729;