chr13-23320654-G-T

Variant names:

• chr13-23320654-G-T
• rs200191311
• NM_000231.3:c.596G>T

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Strong

The NM_000231.3(SGCG):​c.596G>T​(p.Arg199Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000139 in 1,434,806 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R199W) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: SGCG NM_000231.3 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 8.58
• Publications: 0 publications found

Genes affected

SGCG (HGNC:10809): (sarcoglycan gamma) This gene encodes gamma-sarcoglycan, one of several sarcolemmal transmembrane glycoproteins that interact with dystrophin. The dystrophin-glycoprotein complex (DGC) spans the sarcolemma and is comprised of dystrophin, syntrophin, alpha- and beta-dystroglycans and sarcoglycans. The DGC provides a structural link between the subsarcolemmal cytoskeleton and the extracellular matrix of muscle cells. Defects in the encoded protein can lead to early onset autosomal recessive muscular dystrophy, in particular limb-girdle muscular dystrophy, type 2C (LGMD2C). [provided by RefSeq, Oct 2008]

SACS (HGNC:10519): (sacsin molecular chaperone) This gene encodes the sacsin protein, which includes a UbL domain at the N-terminus, a DnaJ domain, and a HEPN domain at the C-terminus. The gene is highly expressed in the central nervous system, also found in skin, skeletal muscles and at low levels in the pancreas. This gene includes a very large exon spanning more than 12.8 kb. Mutations in this gene result in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), a neurodegenerative disorder characterized by early-onset cerebellar ataxia with spasticity and peripheral neuropathy. The authors of a publication on the effects of siRNA-mediated sacsin knockdown concluded that sacsin protects against mutant ataxin-1 and suggest that "the large multi-domain sacsin protein is able to recruit Hsp70 chaperone action and has the potential to regulate the effects of other ataxia proteins" (Parfitt et al., PubMed: 19208651). A pseudogene associated with this gene is located on chromosome 11. Alternative splicing of this gene results in multiple transcript variants. [provided by RefSeq, May 2013]

SACS Gene-Disease associations (from GenCC):

• Charlevoix-Saguenay spastic ataxia

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, G2P, Laboratory for Molecular Medicine, Labcorp Genetics (formerly Invitae), Myriad Women’s Health

LOC107984585 (HGNC:):

ACMG classification

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

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_000231.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.993

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000231.3. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SGCG	NM_000231.3	MANE Select	c.596G>T	p.Arg199Leu	missense	Exon 7 of 8	NP_000222.2
	SGCG	NM_001378244.1		c.650G>T	p.Arg217Leu	missense	Exon 7 of 8	NP_001365173.1
	SGCG	NM_001378245.1		c.596G>T	p.Arg199Leu	missense	Exon 8 of 9	NP_001365174.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SGCG	ENST00000218867.4	TSL:1 MANE Select	c.596G>T	p.Arg199Leu	missense	Exon 7 of 8	ENSP00000218867.3
	SACS	ENST00000682775.1		c.2186-8539C>A		intron	N/A	ENSP00000508399.1
	SACS	ENST00000683210.1		c.2186-31411C>A		intron	N/A	ENSP00000506739.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome AF: 0.00000139 AC: 2 AN: 1434806 Hom.: 0 Cov.: 33 AF XY: 0.00000281 AC XY: 2 AN XY: 712308

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 32700

American (AMR) AF: 0.00 AC: 0 AN: 41974

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25310

East Asian (EAS) AF: 0.00 AC: 0 AN: 39250

South Asian (SAS) AF: 0.0000237 AC: 2 AN: 84246

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51766

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5658

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1094854

Other (OTH) AF: 0.00 AC: 0 AN: 59048

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.0385499), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 31

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.44
BayesDel_addAF	Pathogenic	0.54	D
BayesDel_noAF	Pathogenic	0.54
CADD	Uncertain	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.97	D
Eigen	Pathogenic	0.84
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Pathogenic	0.99	D
M_CAP	Pathogenic	0.41	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.1	M
PhyloP100		8.6
PrimateAI	Uncertain	0.65	T
PROVEAN	Pathogenic	-6.0	D
REVEL	Pathogenic	0.93
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0020	D
Polyphen		1.0	D
Vest4		0.95
MutPred		0.92		Loss of phosphorylation at S202 (P = 0.0662)
MVP		0.98
MPC		0.45
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.76
gMVP		0.80
Mutation Taster		=21/79	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.30		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.30		Position offset: -17

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

Other links and lift over

dbSNP: rs200191311; hg19: chr13-23894793;