rs1553317038

Positions:

• chr2-32128451-T-C
• chr2-32128451-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_014946.4(SPAST):​c.1217T>C​(p.Ile406Thr) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: SPAST NM_014946.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.09

Genes affected

SPAST (HGNC:11233): (spastin) This gene encodes a member of the AAA (ATPases associated with a variety of cellular activities) protein family. Members of this protein family share an ATPase domain and have roles in diverse cellular processes including membrane trafficking, intracellular motility, organelle biogenesis, protein folding, and proteolysis. The use of alternative translational initiation sites in this gene results in a single transcript variant that can produce isoforms that differ in the length of their N-terminus and which thereby differ in the efficiency of their export from the nucleus to the cytoplasm. In addition, alternative splicing results in multiple transcript variants that encode isoforms that differ in other protein regions as well. One isoform of this gene has been shown to be a microtubule-severing enzyme that regulates microtubule abundance, mobility, and plus-end distribution. Mutations in this gene cause the most frequent form of autosomal dominant spastic paraplegia 4. [provided by RefSeq, May 2018]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.962

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SPAST	NM_014946.4	c.1217T>C	p.Ile406Thr	missense_variant	9/17	ENST00000315285.9	NP_055761.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SPAST	ENST00000315285.9	c.1217T>C	p.Ile406Thr	missense_variant	9/17	1	NM_014946.4	ENSP00000320885	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hereditary spastic paraplegia 4 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Feb 02, 2017

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 disruptive, but these predictions have not been confirmed by published functional studies. This sequence change replaces isoleucine with threonine at codon 406 of the SPAST protein (p.Ile406Thr). The isoleucine residue is highly conserved and there is a moderate physicochemical difference between isoleucine and threonine. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a SPAST-related disease. In summary, this variant is a novel missense change with uncertain impact on protein function. It has been classified as a Variant of Uncertain Significance. A different missense substitution at this codon (p.Ile406Thr) has been determined to be pathogenic (PMID: 16682546, 19423133, 16476945). This suggests that the isoleucine residue is critical for SPAST protein function and that other missense substitutions at this position may also be pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.51
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.91	D;D;.;.;.;.;.;.
Eigen	Pathogenic	0.71
Eigen_PC	Pathogenic	0.74
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.97	.;D;D;.;D;D;D;D
M_CAP	Uncertain	0.21	D
MetaRNN	Pathogenic	0.96	D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.99	D
MutationAssessor	Benign	1.8	L;L;.;.;.;.;.;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-4.9	D;.;D;.;.;.;.;.
REVEL	Pathogenic	0.91
Sift	Pathogenic	0.0	D;.;D;.;.;.;.;.
Sift4G	Pathogenic	0.0010	D;D;D;.;.;.;.;.
Polyphen		1.0	D;D;.;.;.;.;.;.
Vest4		0.90
MutPred		0.89		Gain of disorder (P = 0.014);Gain of disorder (P = 0.014);.;.;.;.;.;.;
MVP		0.97
MPC		2.5
ClinPred		1.0	D
GERP RS		5.9
Varity_R		0.91
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: rs1553317038; hg19: chr2-32353520;