2-32137172-G-C

Variant names:

• chr2-32137172-G-C
• rs1060499939
• NM_014946.4:c.1477G>C

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5

The NM_014946.4(SPAST):​c.1477G>C​(p.Asp493His) 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. 13/22 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D493Y) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: SPAST NM_014946.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2
• Conservation: PhyloP100: 8.86
• Publications: 1 publications found

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]

SPAST Gene-Disease associations (from GenCC):

• hereditary spastic paraplegia 4

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), Illumina, Genomics England PanelApp, Ambry Genetics
• Charlevoix-Saguenay spastic ataxia

  Inheritance: AR Classification: DEFINITIVE Submitted by: G2P
• neurodevelopmental disorder

  Inheritance: AD Classification: STRONG Submitted by: G2P
• SPAST-related motor disorder

  Inheritance: AR Classification: STRONG Submitted by: Ambry Genetics

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PM1: In a hotspot region, there are 19 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 14 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 chr2-32137172-G-T is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 417627.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 148 curated pathogenic missense variants (we use a threshold of 10). The gene has 21 curated benign missense variants. Gene score misZ: 1.2438 (below the threshold of 3.09). Trascript score misZ: 0.22274 (below the threshold of 3.09). GenCC associations: The gene is linked to hereditary spastic paraplegia 4, SPAST-related motor disorder, Charlevoix-Saguenay spastic ataxia, neurodevelopmental disorder.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.988
• PP5: Variant 2-32137172-G-C is Pathogenic according to our data. Variant chr2-32137172-G-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 417628.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SPAST	NM_014946.4	c.1477G>C	p.Asp493His	missense_variant	Exon 12 of 17	ENST00000315285.9	NP_055761.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SPAST	ENST00000315285.9	c.1477G>C	p.Asp493His	missense_variant	Exon 12 of 17	1	NM_014946.4	ENSP00000320885.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary spastic paraplegia 4 Pathogenic:1 Uncertain:1

Apr 12, 2017

TIDEX, University of British Columbia

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

There is a second alternative allele (T) as this same base pair location in this patient. -

Apr 03, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

A different missense substitution at this codon (p.Asp493Gly) has been reported to segregate with hereditary spastic paraplegia (HSP) in a single family (PMID: 16682546), but the clinical significance of this variant is uncertain. 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. 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 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. This sequence change replaces aspartic acid with histidine at codon 493 of the SPAST protein (p.Asp493His). The aspartic acid residue is highly conserved and there is a moderate physicochemical difference between aspartic acid and histidine. -

Hereditary spastic paraplegia Uncertain:1

Jun 01, 2020

Genome Diagnostics Laboratory, The Hospital for Sick Children

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Pathogenic	32
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.94	D;D;.;.;.;.;.;.
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Pathogenic	1.0	.;D;D;.;D;D;D;D
M_CAP	Pathogenic	0.38	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.8	H;H;.;.;.;.;.;.
PhyloP100		8.9
PrimateAI	Pathogenic	0.80	T
PROVEAN	Pathogenic	-7.0	D;.;D;.;.;.;.;.
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D;.;D;.;.;.;.;.
Sift4G	Pathogenic	0.0010	D;D;D;.;.;.;.;.
Polyphen		1.0	D;D;.;.;.;.;.;.
Vest4		0.97
MutPred		0.95		Gain of MoRF binding (P = 0.0429);Gain of MoRF binding (P = 0.0429);.;.;.;.;.;.;
MVP		0.96
MPC		2.4
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.97
gMVP		0.95
Mutation Taster		=0/100	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs1060499939; hg19: chr2-32362241;