13-23320654-G-A

Position:

• chr13-23320654-G-A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_000231.3(SGCG):​c.596G>A​(p.Arg199Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000221 in 1,581,020 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.00015 (0 hom., cov: 31)
  • Exomes 𝑓: 0.00023 (1 hom.)
• Consequence: SGCG NM_000231.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:9
• Conservation: PhyloP100: 8.58

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]

LOC107984585 (HGNC:):

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a chain Gamma-sarcoglycan (size 290) in uniprot entity SGCG_HUMAN there are 28 pathogenic changes around while only 1 benign (97%) in NM_000231.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.927

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SGCG	NM_000231.3	c.596G>A	p.Arg199Gln	missense_variant	7/8	ENST00000218867.4	NP_000222.2
LOC107984585	XR_001749787.2	n.2808+912C>T		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SGCG	ENST00000218867.4	c.596G>A	p.Arg199Gln	missense_variant	7/8	1	NM_000231.3	ENSP00000218867	P1
SACS	ENST00000682775.1	c.2186-8539C>T		intron_variant				ENSP00000508399
SACS	ENST00000683210.1	c.2186-31411C>T		intron_variant				ENSP00000506739
SACS	ENST00000684325.1	c.*104+912C>T		intron_variant, NMD_transcript_variant				ENSP00000508121

Frequencies

GnomAD3 genomes AF: 0.000150 AC: 22 AN: 146228 Hom.: 0 Cov.: 31

Gnomad AFR AF: 0.0000261

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000207

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000197

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000252

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000142 AC: 32 AN: 225686 Hom.: 0 AF XY: 0.000148 AC XY: 18 AN XY: 121604

Gnomad AFR exome AF: 0.000142

Gnomad AMR exome AF: 0.0000630

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000352

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000252

Gnomad OTH exome AF: 0.000354

GnomAD4 exome AF: 0.000229 AC: 328 AN: 1434792 Hom.: 1 Cov.: 33 AF XY: 0.000246 AC XY: 175 AN XY: 712300

Gnomad4 AFR exome AF: 0.0000612

Gnomad4 AMR exome AF: 0.0000715

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000255

Gnomad4 SAS exome AF: 0.0000356

Gnomad4 FIN exome AF: 0.0000580

Gnomad4 NFE exome AF: 0.000277

Gnomad4 OTH exome AF: 0.000203

GnomAD4 genome AF: 0.000150 AC: 22 AN: 146228 Hom.: 0 Cov.: 31 AF XY: 0.000169 AC XY: 12 AN XY: 71072

Gnomad4 AFR AF: 0.0000261

Gnomad4 AMR AF: 0.000207

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000197

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000252

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000344 Hom.: 0

Bravo AF: 0.000170

ESP6500AA AF: 0.000227 AC: 1

ESP6500EA AF: 0.000233 AC: 2

ExAC AF: 0.000181 AC: 22

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:9

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Autosomal recessive limb-girdle muscular dystrophy type 2C Uncertain:5

Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Apr 19, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Jan 03, 2023	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Aug 23, 2022	This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 199 of the SGCG protein (p.Arg199Gln). This variant is present in population databases (rs200191311, gnomAD 0.03%). This variant has not been reported in the literature in individuals affected with SGCG-related conditions. ClinVar contains an entry for this variant (Variation ID: 285130). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Jul 06, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Baylor Genetics	Aug 23, 2019	This variant was determined to be of uncertain significance according to ACMG Guidelines, 2015 [PMID:25741868]. -

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Oct 15, 2020	Missense variants in this gene are often considered pathogenic (Stenson et al., 2014); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -
Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Dec 04, 2015	- -

Limb-girdle muscular dystrophy, recessive Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jun 14, 2016

- -

Sarcoglycanopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.13
BayesDel_addAF	Pathogenic	0.33	D
BayesDel_noAF	Pathogenic	0.54
CADD	Pathogenic	27
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.92	D
Eigen	Pathogenic	0.82
Eigen_PC	Pathogenic	0.73
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.33	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.1	M
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.57	T
PROVEAN	Uncertain	-3.4	D
REVEL	Pathogenic	0.85
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0040	D
Polyphen		1.0	D
Vest4		0.91
MVP		0.96
MPC		0.44
ClinPred		0.55	D
GERP RS		5.6
Varity_R		0.58
gMVP		0.75

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.24		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.24		Position offset: -17

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

Publications

LitVar

Other links and lift over

dbSNP: rs200191311; hg19: chr13-23894793;