rs1555538144

chr17-3476248-T-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000049.4(ASPA):c.89T>C(p.Leu30Pro) 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. 12/21 in silico tools predict a damaging 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. L30V) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: ASPA NM_000049.4 missense
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:3 U:1
• Conservation: PhyloP100: 7.79

Genes affected

ASPA (HGNC:756): (aspartoacylase) This gene encodes an enzyme that catalyzes the conversion of N-acetyl_L-aspartic acid (NAA) to aspartate and acetate. NAA is abundant in the brain where hydrolysis by aspartoacylase is thought to help maintain white matter. This protein is an NAA scavenger in other tissues. Mutations in this gene cause Canavan disease. Alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Jul 2008]

SPATA22 (HGNC:30705): (spermatogenesis associated 22) Predicted to be involved in regulation of meiotic cell cycle. Predicted to act upstream of or within several processes, including fertilization; gamete generation; and meiosis I cell cycle process. Predicted to be located in chromosome. [provided by Alliance of Genome Resources, Apr 2022]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 2 uncertain in NM_000049.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr17-3476247-C-G is described in ClinVar as [Pathogenic]. Clinvar id is 2907504.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.99
• PP5: Variant 17-3476248-T-C is Pathogenic according to our data. Variant chr17-3476248-T-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 556181.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ASPA	NM_000049.4	c.89T>C	p.Leu30Pro	missense_variant	1/6	ENST00000263080.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ASPA	ENST00000263080.3	c.89T>C	p.Leu30Pro	missense_variant	1/6	1	NM_000049.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:3 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Spongy degeneration of central nervous system Pathogenic:2 Uncertain:1

Likely pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Uncertain significance, flagged submission	clinical testing	Counsyl	Jan 17, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Invitae	Sep 22, 2019	In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This variant has been reported to affect ASPA protein function (PMID: 28101991). This variant has been observed in the homozygous state in an individual affected with Canavan disease (PMID: 28101991). ClinVar contains an entry for this variant (Variation ID: 556181). This variant is not present in population databases (ExAC no frequency). This sequence change replaces leucine with proline at codon 30 of the ASPA protein (p.Leu30Pro). The leucine residue is highly conserved and there is a moderate physicochemical difference between leucine and proline. -

Canavan Disease, Familial Form Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Jan 11, 2023

Variant summary: ASPA c.89T>C (p.Leu30Pro) results in a non-conservative amino acid change in the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251468 control chromosomes. c.89T>C has been reported in the literature in at least one homozygous individual affected with Canavan Disease (e.g., Mendes_2017). Experimental evidence evaluating an impact on protein function, found that HEK293 cells transfected with the variant protein displayed <1% enzymatic activity (Mendes_2017). These data indicate that the variant is likely to be associated with disease. Three ClinVar submitters (evaluation after 2014) have cited the variant, with two submitters classifying is as likely pathogenic, and one submitter classifying it as uncertain significance. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
Cadd	Pathogenic	32
Dann	Pathogenic	1.0
DEOGEN2	Pathogenic	0.85	D;D;D
Eigen	Pathogenic	0.88
Eigen_PC	Pathogenic	0.82
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Benign	0.85	T;.;D
M_CAP	Pathogenic	0.59	D
MetaRNN	Pathogenic	0.99	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.72	T
Sift4G	Pathogenic	0.0	D;D;D
Polyphen		1.0	.;D;D
Vest4		0.96, 0.97
MutPred		0.94		Loss of stability (P = 0.024);Loss of stability (P = 0.024);Loss of stability (P = 0.024);
MVP		0.99
MPC		0.52
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.98
gMVP		0.98

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: rs1555538144; hg19: chr17-3379542;