NM_000049.4:c.433-2A>G

Variant names:

• chr17-3483497-A-G
• rs63751297
• NM_000049.4:c.433-2A>G

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_000049.4(ASPA):​c.433-2A>G variant causes a splice acceptor, intron change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: ASPA NM_000049.4 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4 O:1
• Conservation: PhyloP100: 6.82
• Publications: 2 publications found

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]

SPATA22 Gene-Disease associations (from GenCC):

• infertility disorder

  Inheritance: AR Classification: MODERATE Submitted by: Ambry Genetics

ACMG classification

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

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.09978768 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.1, offset of -24, new splice context is: acatacggtttttacctaAGaaa. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 17-3483497-A-G is Pathogenic according to our data. Variant chr17-3483497-A-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 40118.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
ASPA	NM_000049.4	c.433-2A>G		splice_acceptor_variant, intron_variant	Intron 2 of 5	ENST00000263080.3	NP_000040.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
ASPA	ENST00000263080.3	c.433-2A>G		splice_acceptor_variant, intron_variant	Intron 2 of 5	1	NM_000049.4	ENSP00000263080.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Spongy degeneration of central nervous system Pathogenic:1 Other:1

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

Feb 09, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

ClinVar contains an entry for this variant (Variation ID: 40118). 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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. Disruption of this splice site has been observed in individual(s) with Canavan disease (PMID: 8023850). This variant is not present in population databases (gnomAD no frequency). This sequence change affects an acceptor splice site in intron 2 of the ASPA gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in ASPA are known to be pathogenic (PMID: 12638939).

Inborn genetic diseases Pathogenic:1

Feb 08, 2021

Ambry Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.433-2A>G intronic variant results from an A to G substitution two nucleotide(s) before coding exon 3 of the ASPA gene. Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. Based on data from the Genome Aggregation Database (gnomAD), the ASPA c.433-2A>G alteration was not observed, with coverage at this position. This mutation was identified in a cohort of individuals with Canavan disease; however, specific genotype and phenotype information was limited (Kaul, 1994). Based on the available evidence, this alteration is classified as likely pathogenic.

not provided Pathogenic:1

Jul 14, 2014

Eurofins Ntd Llc (ga)

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Canavan Disease, Familial Form Pathogenic:1

Mar 17, 2022

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

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: ASPA c.433-2A>G is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes canonical a 3 prime acceptor site. The variant was absent in 251412 control chromosomes (gnomAD). c.433-2A>G has been reported in an heterozygous individual who went through genetic screening for Canavan Disease (example: Kaul_1994). cDNA evaluated from this heterozygous individual confirmed the presence of wild-type and the shorter cDNA product as a result of this variant (Kaul_1994). No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as likely pathogenic.

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.26
CADD	Pathogenic	28
DANN	Uncertain	0.99
DEOGEN2	Benign	0.0	.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.94
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Benign	0.0	.;.
MetaRNN	Benign	0.0	.;.
MutationAssessor	Benign	0.0	.;.
PhyloP100		6.8
PROVEAN	Benign	0.0	.;.
REVEL	Benign	0.0
Sift	Pathogenic	0.0	.;.
Sift4G	Pathogenic	0.0	.;.
Vest4		0.0
GERP RS		5.4
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.98		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.98		Position offset: 2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs63751297; hg19: chr17-3386791;