chr8-1771518-C-A

Position:

• chr8-1771518-C-A

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 8P and 1B. PM1 PM2 PM5 PP5_Moderate BP4

The NM_018941.4(CLN8):​c.464C>A​(p.Ala155Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A155V) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: CLN8 NM_018941.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 0.824

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 7 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 6 uncertain in NM_018941.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr8-1771518-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 56708.Status of the report is no_assertion_criteria_provided, 0 stars.
• PP5: Variant 8-1771518-C-A is Pathogenic according to our data. Variant chr8-1771518-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 422177.Status of the report is criteria_provided_single_submitter, 1 stars.
• BP4: Computational evidence support a benign effect (MetaRNN=0.3499877). . Strength limited to SUPPORTING due to the PP5.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CLN8	NM_018941.4	c.464C>A	p.Ala155Asp	missense_variant	2/3	ENST00000331222.6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CLN8	ENST00000331222.6	c.464C>A	p.Ala155Asp	missense_variant	2/3	1	NM_018941.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Sep 13, 2016

The A155D variant in the CLN8 gene has not been reported previously as a pathogenic variant, nor as a benign variant, to our knowledge. The A155D variant was not observed in approximately 6500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The A155D variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved in mammals. In silico analysis is inconsistent in its predictions as to whether or not the variant is damaging to the protein structure/function. Missense variants in nearby residues (H157R and Y158C) have been reported in the Human Gene Mutation Database in association with neuronal ceroid lipofuscinosis (Stenson et al., 2014), supporting the functional importance of this region of the protein. The A155D variant is a strong candidate for a pathogenic variant, however the possibility it may be a rare benign variant cannot be excluded. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.76
BayesDel_addAF	Uncertain	0.11	D
BayesDel_noAF	Uncertain	-0.080
CADD	Benign	19
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.58	D;D;D;D;.;D;.
Eigen	Benign	-0.044
Eigen_PC	Benign	-0.10
FATHMM_MKL	Benign	0.47	N
LIST_S2	Benign	0.75	.;.;.;.;T;.;T
M_CAP	Uncertain	0.21	D
MetaRNN	Benign	0.35	T;T;T;T;T;T;T
MetaSVM	Uncertain	0.12	D
MutationAssessor	Uncertain	2.2	M;M;M;M;.;M;.
MutationTaster	Benign	0.67	D
PrimateAI	Uncertain	0.49	T
PROVEAN	Benign	-1.1	N;.;.;.;.;.;.
REVEL	Uncertain	0.48
Sift	Benign	0.16	T;.;.;.;.;.;.
Sift4G	Benign	0.15	T;.;.;.;.;.;T
Polyphen		0.84	P;P;P;P;.;P;.
Vest4		0.49
MutPred		0.34		Gain of sheet (P = 0.0221);Gain of sheet (P = 0.0221);Gain of sheet (P = 0.0221);Gain of sheet (P = 0.0221);Gain of sheet (P = 0.0221);Gain of sheet (P = 0.0221);Gain of sheet (P = 0.0221);
MVP		0.89
MPC		0.31
ClinPred		0.49	T
GERP RS		4.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.18
gMVP		0.73

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

Publications

LitVar

Other links and lift over

dbSNP: rs386834128; hg19: chr8-1719684;