15-90747387-A-T

Position:

• chr15-90747387-A-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PVS1_Moderate PM2 PP3_Strong

The NM_000057.4(BLM):​c.-4-2A>T variant causes a splice acceptor change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (no stars).

• Frequency: Genomes: not found (cov: 31)
• Consequence: BLM NM_000057.4 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance no assertion criteria provided U:1
• Conservation: PhyloP100: 2.10

Genes affected

BLM (HGNC:1058): (BLM RecQ like helicase) The Bloom syndrome is an autosomal recessive disorder characterized by growth deficiency, microcephaly and immunodeficiency among others. It is caused by homozygous or compound heterozygous mutation in the gene encoding DNA helicase RecQ protein on chromosome 15q26. This Bloom-associated helicase unwinds a variety of DNA substrates including Holliday junction, and is involved in several pathways contributing to the maintenance of genome stability. Identification of pathogenic Bloom variants is required for heterozygote testing in at-risk families. [provided by RefSeq, May 2020]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PVS1: Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 0.023742361 fraction of the gene. Cryptic splice site detected, with MaxEntScore 5.2, offset of 34, new splice context is: ttcctcaaaataatctacAGgag. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.-4-2A>T		splice_acceptor_variant		ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.-4-2A>T		splice_acceptor_variant		1	NM_000057.4	P2

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 31

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: no assertion criteria provided

Submissions by phenotype

Bloom syndrome Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

Natera, Inc.

Sep 04, 2020

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Pathogenic	0.18
CADD	Pathogenic	27
DANN	Uncertain	0.98

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.89		Details are displayed if max score is > 0.2
DS_AL_spliceai		0.89		Position offset: 2

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

Publications

LitVar

Other links and lift over

dbSNP: rs866546098; hg19: chr15-91290617;