2-32137178-G-A

Position:

• chr2-32137178-G-A

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_014946.4(SPAST):​c.1483G>A​(p.Ala495Thr) variant causes a missense change involving the alteration of a conserved nucleotide. 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 Pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A495P) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SPAST NM_014946.4 missense
• Clinical Significance: Pathogenic criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: 8.86

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 Pathogenic. Variant got 12 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_014946.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr2-32137179-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 488606.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.975
• PP5: Variant 2-32137178-G-A is Pathogenic according to our data. Variant chr2-32137178-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 409032.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SPAST	NM_014946.4	c.1483G>A	p.Ala495Thr	missense_variant	12/17	ENST00000315285.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SPAST	ENST00000315285.9	c.1483G>A	p.Ala495Thr	missense_variant	12/17	1	NM_014946.4	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hereditary spastic paraplegia 4 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 19, 2023

For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Ala495 amino acid residue in SPAST. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 31157359, 32989326). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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 SPAST protein function. ClinVar contains an entry for this variant (Variation ID: 409032). This missense change has been observed in individual(s) with hereditary spastic paraplegia (Invitae). In at least one individual the variant was observed to be de novo. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 495 of the SPAST protein (p.Ala495Thr). -

SPAST-related disorder Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Jan 11, 2024

The SPAST c.1483G>A variant is predicted to result in the amino acid substitution p.Ala495Thr. To our knowledge, this variant has not been reported in the literature or in a large population database, indicating this variant is rare. Alternate nucleotide changes affecting the same amino acid (p.Ala495Pro and p.Ala495Val) have been reported in individuals with spastic paraplegia and dystonia (Table 2, de novo, Schieving et al. 2019. PubMed ID: 31157359; Table S2, Sup. Fig. 16, de novo, Zech et al. 2020. PubMed ID: 33098801 ). Although we suspect that the c.1483G>A (p.Ala495Thr) variant is pathogenic, at this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.36
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.93	D;D;.;.;.;.;.;.
Eigen	Pathogenic	0.85
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Pathogenic	0.99	.;D;D;.;D;D;D;D
M_CAP	Pathogenic	0.37	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.5	M;M;.;.;.;.;.;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.74	T
PROVEAN	Uncertain	-4.0	D;.;D;.;.;.;.;.
REVEL	Pathogenic	0.92
Sift	Pathogenic	0.0	D;.;D;.;.;.;.;.
Sift4G	Uncertain	0.0030	D;D;D;.;.;.;.;.
Polyphen		0.99	D;D;.;.;.;.;.;.
Vest4		0.88
MutPred		0.86		Gain of MoRF binding (P = 0.1233);Gain of MoRF binding (P = 0.1233);.;.;.;.;.;.;
MVP		0.90
MPC		2.1
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.95
gMVP		0.92

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: rs1060502228; hg19: chr2-32362247;