chr5-70946145-A-G

Variant names:

• chr5-70946145-A-G
• rs1554082113
• NM_000344.4:c.803A>G

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PP2 PP3_Strong PP5

The NM_000344.4(SMN1):​c.803A>G​(p.Tyr268Cys) variant causes a missense change involving the alteration of a conserved nucleotide. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 0)
• Consequence: SMN1 NM_000344.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 8.49
• Publications: 0 publications found

Genes affected

SMN1 (HGNC:11117): (survival of motor neuron 1, telomeric) This gene is part of a 500 kb inverted duplication on chromosome 5q13. This duplicated region contains at least four genes and repetitive elements which make it prone to rearrangements and deletions. The repetitiveness and complexity of the sequence have also caused difficulty in determining the organization of this genomic region. The telomeric and centromeric copies of this gene are nearly identical and encode the same protein. However, mutations in this gene, the telomeric copy, are associated with spinal muscular atrophy; mutations in the centromeric copy do not lead to disease. The centromeric copy may be a modifier of disease caused by mutation in the telomeric copy. The critical sequence difference between the two genes is a single nucleotide in exon 7, which is thought to be an exon splice enhancer. Note that the nine exons of both the telomeric and centromeric copies are designated historically as exon 1, 2a, 2b, and 3-8. It is thought that gene conversion events may involve the two genes, leading to varying copy numbers of each gene. The protein encoded by this gene localizes to both the cytoplasm and the nucleus. Within the nucleus, the protein localizes to subnuclear bodies called gems which are found near coiled bodies containing high concentrations of small ribonucleoproteins (snRNPs). This protein forms heteromeric complexes with proteins such as SIP1 and GEMIN4, and also interacts with several proteins known to be involved in the biogenesis of snRNPs, such as hnRNP U protein and the small nucleolar RNA binding protein. Multiple transcript variants encoding distinct isoforms have been described. [provided by RefSeq, Jul 2014]

SMN1 Gene-Disease associations (from GenCC):

• spinal muscular atrophy

  Inheritance: AR Classification: DEFINITIVE Submitted by: Myriad Women’s Health
• spinal muscular atrophy, type 1

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Orphanet, Genomics England PanelApp
• spinal muscular atrophy, type II

  Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Orphanet
• spinal muscular atrophy, type III

  Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Orphanet
• spinal muscular atrophy, type IV

  Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 10 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 0 uncertain in NM_000344.4
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 25 curated pathogenic missense variants (we use a threshold of 10). The gene has 0 curated benign missense variants. Gene score misZ: 0.058423 (below the threshold of 3.09). Trascript score misZ: 0.12361 (below the threshold of 3.09). GenCC associations: The gene is linked to spinal muscular atrophy, type III, spinal muscular atrophy, type IV, spinal muscular atrophy, type 1, spinal muscular atrophy, spinal muscular atrophy, type II.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.988
• PP5: Variant 5-70946145-A-G is Pathogenic according to our data. Variant chr5-70946145-A-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 448430.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMN1	NM_000344.4	c.803A>G	p.Tyr268Cys	missense_variant	Exon 7 of 9	ENST00000380707.9	NP_000335.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMN1	ENST00000380707.9	c.803A>G	p.Tyr268Cys	missense_variant	Exon 7 of 9	1	NM_000344.4	ENSP00000370083.4

Frequencies

GnomAD3 genomes Cov.: 0

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 0

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Spinal muscular atrophy Pathogenic:1

Feb 02, 2022

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Likely pathogenic. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with spinal muscular atrophy. (I) 0106 - This gene is associated with autosomal recessive disease. (I) 0200 - Variant is predicted to result in a missense amino acid change from tyrosine to cysteine. (I) 0253 - This variant is hemizygous. (I) 0301 - Variant is absent from gnomAD (both v2 and v3). (SP) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0602 - Variant is located in a hotspot region or cluster of pathogenic variants. This variant is located in the YG-box domain and part of a conserved tyrosine side chain motif (PMID: 23022347). The YG-box domain is part of the critical C-terminal domain which enables self-association, governs stability and facilitates subcellular localization of SMN (PMID: 27481219). A cluster of pathogenic variants have been reported in exon 7 (ClinVar). (SP) 0705 - No comparable missense variants have previous evidence for pathogenicity. (I) 0809 - Previous evidence of pathogenicity for this variant is inconclusive. This variant has been reported as a VUS in ClinVar. (I) 0905 - No published segregation evidence has been identified for this variant. (I) 1007 - No published functional evidence has been identified for this variant. (I) 1201 - Heterozygous variant detected in trans with a second pathogenic heterozygous variant (exon 7 SMN1 deletion) in a recessive disease. (SP) 1205 - This variant has been shown to be maternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -

not specified Uncertain:1

May 30, 2017

Athena Diagnostics

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	0.99
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.58
CADD	Pathogenic	30
DANN	Uncertain	0.98
DEOGEN2	Pathogenic	0.91	.;D;D;.;D;D
Eigen	Uncertain	0.31
Eigen_PC	Uncertain	0.32
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.99	D;.;D;D;D;D
M_CAP	Pathogenic	0.91	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D
MetaSVM	Pathogenic	0.99	D
PhyloP100		8.5
PrimateAI	Pathogenic	0.86	D
PROVEAN	Pathogenic	-7.9	D;D;D;D;.;.
REVEL	Pathogenic	0.98
Sift	Pathogenic	0.0	D;D;D;D;.;.
Sift4G	Pathogenic	0.0	D;D;D;D;D;D
Vest4		0.93
MutPred		0.89		.;Loss of phosphorylation at Y268 (P = 0.1118);.;Loss of phosphorylation at Y268 (P = 0.1118);Loss of phosphorylation at Y268 (P = 0.1118);Loss of phosphorylation at Y268 (P = 0.1118);
MVP		0.99
MPC		2.1
ClinPred		1.0	D
GERP RS		3.4
Varity_R		0.97
gMVP		0.96
Mutation Taster		=8/92	disease causing

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: rs1554082113; hg19: chr5-70241972;