1-25800233-G-GGCCC

Position:

• chr1-25800233-G-GGCCC

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1 PM2 PP5_Moderate

The NM_020451.3(SELENON):​c.4_5insCCCG​(p.Gly2fs) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency: Genomes: not found (cov: 30)
• Consequence: SELENON NM_020451.3 frameshift
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: -0.219

Genes affected

SELENON (HGNC:15999): (selenoprotein N) This gene encodes a glycoprotein that is localized in the endoplasmic reticulum. It plays an important role in cell protection against oxidative stress, and in the regulation of redox-related calcium homeostasis. Mutations in this gene are associated with early onset muscle disorders, referred to as SEPN1-related myopathy. SEPN1-related myopathy consists of 4 autosomal recessive disorders, originally thought to be separate entities: rigid spine muscular dystrophy (RSMD1), the classical form of multiminicore disease, desmin related myopathy with Mallory-body like inclusions, and congenital fiber-type disproportion (CFTD). This protein is a selenoprotein, containing the rare amino acid selenocysteine (Sec). Sec is encoded by the UGA codon, which normally signals translation termination. The 3' UTRs of selenoprotein mRNAs contain a conserved stem-loop structure, designated the Sec insertion sequence (SECIS) element, that is necessary for the recognition of UGA as a Sec codon, rather than as a stop signal. A second stop-codon redefinition element (SRE) adjacent to the UGA codon has been identified in this gene (PMID:15791204). SRE is a phylogenetically conserved stem-loop structure that stimulates readthrough at the UGA codon, and augments the Sec insertion efficiency by SECIS. Alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Dec 2016]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 144 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-25800233-G-GGCCC is Pathogenic according to our data. Variant chr1-25800233-G-GGCCC is described in ClinVar as [Pathogenic]. Clinvar id is 3366830.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SELENON	NM_020451.3	c.4_5insCCCG	p.Gly2fs	frameshift_variant	1/13	ENST00000361547.7	NP_065184.2
SELENON	NM_206926.2	c.4_5insCCCG	p.Gly2fs	frameshift_variant	1/12		NP_996809.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SELENON	ENST00000361547.7	c.4_5insCCCG	p.Gly2fs	frameshift_variant	1/13	1	NM_020451.3	ENSP00000355141.2
SELENON	ENST00000374315.1	c.4_5insCCCG	p.Gly2fs	frameshift_variant	1/12	5		ENSP00000363434.1
SELENON	ENST00000354177.9	c.4_5insCCCG	p.Gly2fs	frameshift_variant	1/12	5		ENSP00000346109.5
SELENON	ENST00000494537.2	n.4_5insCCCG		non_coding_transcript_exon_variant	1/13	3		ENSP00000508308.1

Frequencies

GnomAD3 genomes Cov.: 30

GnomAD4 exome Cov.: 8

GnomAD4 genome Cov.: 30

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Eichsfeld type congenital muscular dystrophy Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

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

Aug 13, 2024

Variant summary: SELENON c.4_5insCCCG (p.Gly2AlafsX82) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. The frequency data for this variant in gnomAD is considered unreliable, as metrics indicate poor data quality at this position. To our knowledge, no occurrence of c.4_5insCCCG in individuals affected with Eichsfeld Type Congenital Muscular Dystrophy and no experimental evidence demonstrating its impact on protein function have been reported. No submitters have cited clinical-significance assessments for this variant to ClinVar. Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

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

Publications

No publications associated with this variant yet.

Other links and lift over

hg19: chr1-26126724;