rs104893933

Variant names:

• chr5-70942430-A-T
• rs104893933
• NM_000344.4:c.346A>T

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PM5 PP2 PP3 PP5_Very_Strong

The NM_000344.4(SMN1):​c.346A>T​(p.Ile116Phe) variant causes a missense change involving the alteration of a non-conserved nucleotide. 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. I116T) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 0)
• Consequence: SMN1 NM_000344.4 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: -0.749
• Publications: 5 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: Orphanet, Genomics England PanelApp, Ambry Genetics
• spinal muscular atrophy, type II

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

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

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

ACMG classification

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

• PM5: Other missense variant is known to change same aminoacid residue: Variant chr5-70942431-T-C is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 3239631.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• 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, 0.823
• PP5: Variant 5-70942430-A-T is Pathogenic according to our data. Variant chr5-70942430-A-T is described in ClinVar as Pathogenic. ClinVar VariationId is 9179.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000344.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SMN1	NM_000344.4	MANE Select	c.346A>T	p.Ile116Phe	missense	Exon 4 of 9	NP_000335.1	Q16637-1
	SMN1	NM_001297715.1		c.346A>T	p.Ile116Phe	missense	Exon 4 of 8	NP_001284644.1	Q16637-3
	SMN1	NM_022874.2		c.346A>T	p.Ile116Phe	missense	Exon 4 of 8	NP_075012.1	Q16637-2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SMN1	ENST00000380707.9	TSL:1 MANE Select	c.346A>T	p.Ile116Phe	missense	Exon 4 of 9	ENSP00000370083.4	Q16637-1
	SMN1	ENST00000351205.8	TSL:1	c.346A>T	p.Ile116Phe	missense	Exon 4 of 8	ENSP00000305857.5	Q16637-1
	SMN1	ENST00000506163.5	TSL:1	c.346A>T	p.Ile116Phe	missense	Exon 4 of 8	ENSP00000424926.1	Q16637-3

Frequencies

GnomAD3 genomes Cov.: 0

GnomAD4 exome Cov.: 0

GnomAD4 genome Cov.: 0

ClinVar

ClinVar submissions as Germline

Significance: Pathogenic

Revision: criteria provided, multiple submitters, no conflicts

Pathogenic	VUS	Benign	Condition
2	-	-	not provided (2)
1	-	-	Werdnig-Hoffmann disease (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.29
BayesDel_addAF	Uncertain	0.13	D
BayesDel_noAF	Uncertain	-0.050
CADD	Benign	2.8
DANN	Benign	0.91
DEOGEN2	Pathogenic	0.81	D
Eigen	Benign	-1.3
Eigen_PC	Benign	-1.6
FATHMM_MKL	Benign	0.066	N
LIST_S2	Uncertain	0.86	D
M_CAP	Pathogenic	0.30	D
MetaRNN	Pathogenic	0.82	D
MetaSVM	Pathogenic	0.85	D
PhyloP100		-0.75
PrimateAI	Benign	0.30	T
PROVEAN	Uncertain	-3.3	D
REVEL	Uncertain	0.52
Sift	Uncertain	0.027	D
Sift4G	Benign	0.096	T
Vest4		0.41
MutPred		0.83		Gain of catalytic residue at I116 (P = 0.0087)
MVP		0.95
MPC		2.1
ClinPred		0.30	T
GERP RS		-6.9
Varity_R		0.53
gMVP		0.62
Mutation Taster		=4/96	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.23		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.23		Position offset: 12

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

Other links and lift over

dbSNP: rs104893933; hg19: chr5-70238257;