rs878854977

Positions:

• chr13-23333168-T-A

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_014363.6(SACS):​c.10708A>T​(p.Ile3570Leu) 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. 16/21 in silico tools predict a benign 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. I3570T) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: SACS NM_014363.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.17

Genes affected

SACS (HGNC:10519): (sacsin molecular chaperone) This gene encodes the sacsin protein, which includes a UbL domain at the N-terminus, a DnaJ domain, and a HEPN domain at the C-terminus. The gene is highly expressed in the central nervous system, also found in skin, skeletal muscles and at low levels in the pancreas. This gene includes a very large exon spanning more than 12.8 kb. Mutations in this gene result in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), a neurodegenerative disorder characterized by early-onset cerebellar ataxia with spasticity and peripheral neuropathy. The authors of a publication on the effects of siRNA-mediated sacsin knockdown concluded that sacsin protects against mutant ataxin-1 and suggest that "the large multi-domain sacsin protein is able to recruit Hsp70 chaperone action and has the potential to regulate the effects of other ataxia proteins" (Parfitt et al., PubMed: 19208651). A pseudogene associated with this gene is located on chromosome 11. Alternative splicing of this gene results in multiple transcript variants. [provided by RefSeq, May 2013]

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.15971455).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SACS	NM_014363.6	c.10708A>T	p.Ile3570Leu	missense_variant	10/10	ENST00000382292.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SACS	ENST00000382292.9	c.10708A>T	p.Ile3570Leu	missense_variant	10/10	5	NM_014363.6	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Spastic paraplegia Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jul 24, 2019

Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a SACS-related disease. This sequence change replaces isoleucine with leucine at codon 3570 of the SACS protein (p.Ile3570Leu). The isoleucine residue is weakly conserved and there is a small physicochemical difference between isoleucine and leucine. In summary, this is a novel missense change that is not predicted to affect protein function or cause disease. However, the evidence is insufficient at this time to prove that conclusively. It has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.074
BayesDel_addAF	Benign	-0.026	T
BayesDel_noAF	Benign	-0.27
CADD	Benign	19
DANN	Benign	0.95
Eigen	Benign	-0.29
Eigen_PC	Benign	-0.028
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Benign	0.86	D;D
M_CAP	Benign	0.015	T
MetaRNN	Benign	0.16	T;T
MetaSVM	Benign	-0.81	T
MutationTaster	Benign	0.96	N;N;N
PrimateAI	Benign	0.39	T
PROVEAN	Benign	-0.28	N;N
REVEL	Benign	0.20
Sift	Benign	0.099	T;T
Sift4G	Benign	0.062	T;D
Polyphen		0.0090	.;B
Vest4		0.10
MutPred		0.32		.;Gain of catalytic residue at H3575 (P = 0.009);
MVP		0.73
ClinPred		0.49	T
GERP RS		5.9
Varity_R		0.11
gMVP		0.17

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: rs878854977; hg19: chr13-23907307;