21-33550717-GC-G

Variant names:

• chr21-33550717-GC-G
• rs1555898280
• NM_138927.4:c.1487delC

Variant summary

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

The NM_138927.4(SON):​c.1487delC​(p.Ala496GlyfsTer2) 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 (★). Synonymous variant affecting the same amino acid position (i.e. A496A) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 33)
• Consequence: SON NM_138927.4 frameshift
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: -1.78

Genes affected

SON (HGNC:11183): (SON DNA and RNA binding protein) This gene encodes a protein that contains multiple simple repeats. The encoded protein binds RNA and promotes pre-mRNA splicing, particularly of transcripts with poor splice sites. The protein also recognizes a specific DNA sequence found in the human hepatitis B virus (HBV) and represses HBV core promoter activity. There is a pseudogene for this gene on chromosome 1. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2013]

MIR6501 (HGNC:50033): (microRNA 6501) microRNAs (miRNAs) are short (20-24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. miRNAs are transcribed by RNA polymerase II as part of capped and polyadenylated primary transcripts (pri-miRNAs) that can be either protein-coding or non-coding. The primary transcript is cleaved by the Drosha ribonuclease III enzyme to produce an approximately 70-nt stem-loop precursor miRNA (pre-miRNA), which is further cleaved by the cytoplasmic Dicer ribonuclease to generate the mature miRNA and antisense miRNA star (miRNA*) products. The mature miRNA is incorporated into a RNA-induced silencing complex (RISC), which recognizes target mRNAs through imperfect base pairing with the miRNA and most commonly results in translational inhibition or destabilization of the target mRNA. The RefSeq represents the predicted microRNA stem-loop. [provided by RefSeq, Sep 2009]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 21-33550717-GC-G is Pathogenic according to our data. Variant chr21-33550717-GC-G is described in ClinVar as [Pathogenic]. Clinvar id is 504062.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SON	NM_138927.4	c.1487delC	p.Ala496GlyfsTer2	frameshift_variant	Exon 3 of 12	ENST00000356577.10	NP_620305.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SON	ENST00000356577.10	c.1487delC	p.Ala496GlyfsTer2	frameshift_variant	Exon 3 of 12	1	NM_138927.4	ENSP00000348984.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Jan 12, 2018

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.1487delC variant in the SON gene has not been reported previously as a pathogenic variant nor as a benign variant, to our knowledge. The c.1487delC variant causes a frameshift starting with codon Alanine 496, changes this amino acid to a Glycine residue, and creates a premature Stop codon at position 2 of the new reading frame, denoted p.Ala496GlyfsX2. This variant is predicted to cause loss of normal protein function either through protein truncation or nonsense-mediated mRNA decay. The c.1487delC variant is not observed in large population cohorts (Lek et al., 2016). We interpret c.1487delC as a pathogenic variant. -

Computational scores

Source: dbNSFP v4.3

Splicing

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555898280; hg19: chr21-34923023;