chr15-90760731-T-G

Position:

• chr15-90760731-T-G

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000057.4(BLM):​c.1358T>G​(p.Leu453Ter) variant causes a stop gained 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. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BLM NM_000057.4 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 0.429

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 Pathogenic. Variant got 18 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 15-90760731-T-G is Pathogenic according to our data. Variant chr15-90760731-T-G is described in ClinVar as [Pathogenic]. Clinvar id is 182059.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BLM	NM_000057.4	c.1358T>G	p.Leu453Ter	stop_gained	7/22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.1358T>G	p.Leu453Ter	stop_gained	7/22	1	NM_000057.4	ENSP00000347232	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Apr 22, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 31, 2019	This variant has not been reported in the literature in individuals with BLM-related conditions. ClinVar contains an entry for this variant (Variation ID: 182059). This variant is not present in population databases (ExAC no frequency). This sequence change creates a premature translational stop signal (p.Leu453*) in the BLM gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in BLM are known to be pathogenic (PMID: 17407155). For these reasons, this variant has been classified as Pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 28, 2019

The p.L453* pathogenic mutation (also known as c.1358T>G), located in coding exon 6 of the BLM gene, results from a T to G substitution at nucleotide position 1358. This changes the amino acid from a leucine to a stop codon within coding exon 6. This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Uncertain	0.050
CADD	Pathogenic	28
DANN	Benign	0.97
Eigen	Benign	-0.011
Eigen_PC	Benign	-0.33
FATHMM_MKL	Benign	0.12	N
MutationTaster	Benign	1.0	A;A
Vest4		0.97
GERP RS		2.1
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs730881428; hg19: chr15-91303961;