chr4-76168400-T-TA

Variant names:

• chr4-76168400-T-TA
• rs727502783
• NM_005506.4:c.1187+2dupT

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PVS1 PM2 PP5

The NM_005506.4(SCARB2):​c.1187+2dupT variant causes a splice donor, intron change. The variant allele was found at a frequency of 0.00000137 in 1,461,240 control chromosomes in the GnomAD database, with no homozygous occurrence. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: SCARB2 NM_005506.4 splice_donor, intron
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:2
• Conservation: PhyloP100: 6.84
• Publications: 0 publications found

Genes affected

SCARB2 (HGNC:1665): (scavenger receptor class B member 2) The protein encoded by this gene is a type III glycoprotein that is located primarily in limiting membranes of lysosomes and endosomes. Earlier studies in mice and rat suggested that this protein may participate in membrane transportation and the reorganization of endosomal/lysosomal compartment. The protein deficiency in mice was reported to impair cell membrane transport processes and cause pelvic junction obstruction, deafness, and peripheral neuropathy. Further studies in human showed that this protein is a ubiquitously expressed protein and that it is involved in the pathogenesis of HFMD (hand, foot, and mouth disease) caused by enterovirus-71 and possibly by coxsackievirus A16. Mutations in this gene caused an autosomal recessive progressive myoclonic epilepsy-4 (EPM4), also known as action myoclonus-renal failure syndrome (AMRF). Alternatively spliced transcript variants encoding different isoforms have been found for this gene.[provided by RefSeq, Feb 2011]

SCARB2 Gene-Disease associations (from GenCC):

• action myoclonus-renal failure syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Ambry Genetics, Orphanet, Labcorp Genetics (formerly Invitae)
• progressive myoclonus epilepsy

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• Unverricht-Lundborg syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ENSG00000286074 (HGNC:58820):

ACMG classification

Our verdict: Pathogenic. The variant received 11 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 4-76168400-T-TA is Pathogenic according to our data. Variant chr4-76168400-T-TA is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 30259.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_005506.4. 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
	SCARB2	NM_005506.4	MANE Select	c.1187+2dupT		splice_donor intron	N/A	NP_005497.1
	SCARB2	NM_001204255.2		c.758+2dupT		splice_donor intron	N/A	NP_001191184.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SCARB2	ENST00000264896.8	TSL:1 MANE Select	c.1187+2dupT		splice_donor intron	N/A	ENSP00000264896.2
	SCARB2	ENST00000640634.1	TSL:5	c.1307+2dupT		splice_donor intron	N/A	ENSP00000492737.1
	SCARB2	ENST00000639145.1	TSL:5	c.1178+2dupT		splice_donor intron	N/A	ENSP00000492831.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000796 AC: 2 AN: 251394 AF XY: 0.00

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461240 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 726990

African (AFR) AF: 0.00 AC: 0 AN: 33454

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26132

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86248

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53402

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1111428

Other (OTH) AF: 0.00 AC: 0 AN: 60386

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Action myoclonus-renal failure syndrome Pathogenic:3

Mar 05, 2015

GeneReviews

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

Jun 01, 2011

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

May 25, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

not specified Uncertain:1

Feb 11, 2025

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

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: SCARB2 c.1187+2dupT also known as c.1187+3insT, alters a conserved nucleotide located close to a canonical splice site and therefore could affect mRNA splicing, leading to a significantly altered protein sequence. Several computational tools predict a significant impact on normal splicing: Three predict the variant abolishes the canonical 5' splicing donor site. One predict the variant no significant impact on splicing. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 8e-06 in 251394 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.1187+2dupT has been reported in the literature in one individual affected withprogressive myoclonus epilepsy and demyelinating peripheral neuropathy. These data do not allow any conclusion about variant significance. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publication has been ascertained in the context of this evaluation (PMID: 21670406). ClinVar contains an entry for this variant (Variation ID: 30259). Based on the evidence outlined above, the variant was classified as uncertain significance.

Progressive myoclonic epilepsy Uncertain:1

Aug 29, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change falls in intron 9 of the SCARB2 gene. It does not directly change the encoded amino acid sequence of the SCARB2 protein. It affects a nucleotide within the consensus splice site. This variant is present in population databases (rs727502783, gnomAD 0.002%). This variant has been observed in individual(s) with progressive myoclonic epilepsy without renal failure (PMID: 21670406). This variant is also known as c.1187+3insT. ClinVar contains an entry for this variant (Variation ID: 30259). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). 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.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		6.8
Mutation Taster		=17/83	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.97		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.97		Position offset: 3

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

Other links and lift over

dbSNP: rs727502783; hg19: chr4-77089553;