chr15-90769196-C-T

Variant names:

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2BS1_Supporting

The NM_000057.4(BLM):c.2371C>T(p.Arg791Cys) variant causes a missense change. The variant allele was found at a frequency of 0.0000868 in 1,613,678 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000089 ( 0 hom. )

Consequence

BLM
NM_000057.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:9B:1O:1

Conservation

PhyloP100: 4.85

Variant links:

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]

BLM links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 1 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BS1

Variant frequency is greater than expected in population eas. gnomad4 allele frequency = 0.0000657 (10/152280) while in subpopulation EAS AF= 0.00154 (8/5182). AF 95% confidence interval is 0.000768. There are 0 homozygotes in gnomad4. There are 6 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BLM	NM_000057.4 link	c.2371C>T	p.Arg791Cys	missense_variant	Exon 11 of 22	ENST00000355112.8	NP_000048.1	P54132

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8 link	c.2371C>T	p.Arg791Cys	missense_variant	Exon 11 of 22	1	NM_000057.4	ENSP00000347232.3		P54132

Frequencies

GnomAD3 genomes

AF:

0.0000723

AC:

AN:

152162

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.000288

Gnomad EAS

AF:

0.00173

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.000131

AC:

AN:

251468

Hom.:

AF XY:

0.000103

AC XY:

AN XY:

135906

show subpopulations

Gnomad AFR exome

AF:

0.0000615

Gnomad AMR exome

AF:

0.0000289

Gnomad ASJ exome

AF:

0.000298

Gnomad EAS exome

AF:

0.00130

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000176

Gnomad OTH exome

AF:

0.000326

GnomAD4 exome

AF:

0.0000890

AC:

130

AN:

1461398

Hom.:

Cov.:

AF XY:

0.0000922

AC XY:

AN XY:

727014

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.000421

Gnomad4 EAS exome

AF:

0.00227

Gnomad4 SAS exome

AF:

0.0000696

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.0000135

Gnomad4 OTH exome

AF:

0.000116

GnomAD4 genome

AF:

0.0000657

AC:

AN:

152280

Hom.:

Cov.:

AF XY:

0.0000806

AC XY:

AN XY:

74442

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.000288

Gnomad4 EAS

AF:

0.00154

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000147

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.000122

Hom.:

Bravo

AF:

0.0000945

ESP6500AA

AF:

0.000227

AC:

ESP6500EA

AF:

0.000116

AC:

ExAC

AF:

0.000148

AC:

Asia WGS

AF:

0.000866

AC:

AN:

3478

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:9Benign:1Other:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Bloom syndrome

Uncertain:5

Uncertain significance, criteria provided, single submitter	clinical testing	Pars Genome Lab	May 18, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Mar 13, 2017	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Oct 31, 2018	- -
Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Feb 02, 2025	This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 791 of the BLM protein (p.Arg791Cys). This variant is present in population databases (rs55880859, gnomAD 0.1%). This variant has not been reported in the literature in individuals affected with BLM-related conditions. ClinVar contains an entry for this variant (Variation ID: 133698). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is not expected to disrupt BLM protein function with a negative predictive value of 80%. Experimental studies have shown that this missense change affects BLM function (PMID: 23129629, 24816114, 26788541). 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. -

Hereditary cancer-predisposing syndrome

Uncertain:1Benign:1

Likely benign, criteria provided, single submitter	clinical testing	Ambry Genetics	Feb 15, 2023	This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -
Uncertain significance, criteria provided, single submitter	curation	Sema4, Sema4	Oct 12, 2021	- -

not specified

Uncertain:1Other:1

not provided, no classification provided	reference population	ITMI	Sep 19, 2013	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Feb 23, 2018	Variant summary: BLM c.2371C>T (p.Arg791Cys) results in a non-conservative amino acid change located in the Helicase superfamily 1/2, ATP-binding domain and DEAD/DEAH box helicase domain of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00012 in 277226 control chromosomes. This frequency is not higher than expected for a pathogenic variant in BLM causing Bloom Syndrome (0.00012 vs 0.0035), allowing no conclusion about variant significance. The c.2371C>T variant has been reported in the literature in a cancer cell line from a Bloom Syndrome patient. This report does not provide strong evidence about an association of the variant with Bloom Syndrome. Several publications report experimental evidence evaluating an impact on protein function. In one study (Shastri_2015), the variant showed no significant sensitivity to hydroxyurea. However, it showed delayed accumulation and elimination of phosphorylated H2AX upon DNA damage. Moreover, the variant showed a significantly increased level of sister chromatid exchanges compared WT controls. Another study (Mirzaei_2012) described the variant as a partial loss of function via yeast growth assays, and suggested this was due to the variants proximity to an invariant residue (D795), thus causing only a partial loss of ATP hydrolysis activity. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, and classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Sep 08, 2024

The BLM c.2371C>T (p.Arg791Cys) variant has been reported in the published literature in experimental studies with inconclusive functional evidence. It is noted to result in partial loss of function in yeast based assays (PMID: 23129629 (2012)). Additionally, it is described to destabilize the enzyme and lead to inefficient DNA break repair (PMIDs: 24816114 (2014), 26788541 (2016)). However, it is also noted to show normal cell survival with unclear sensitivity to certain cancer medications (PMID: 26788541 (2016)). Further evidence is needed. To the best of our knowledge, this variant has not been reported in individuals with BLM-associated disease. The frequency of this variant in the general population, 0.0013 (25/19954 chromosomes in East Asian subpopulation (Genome Aggregation Database, http://gnomad.broadinstitute.org)), is higher than would generally be expected for pathogenic variants in this gene. Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded predictions that this variant is damaging. Based on the available information, we are unable to determine the clinical significance of this variant. -

Hereditary breast ovarian cancer syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

research

Cancer Genomics Group, Japanese Foundation For Cancer Research

May 01, 2019

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.28

BayesDel_addAF

Benign

-0.083

BayesDel_noAF

Uncertain

0.070

CADD

Pathogenic

DANN

Pathogenic

1.0

DEOGEN2

Benign

0.37

T;.

Eigen

Pathogenic

0.80

Eigen_PC

Pathogenic

0.75

FATHMM_MKL

Uncertain

0.97

LIST_S2

Uncertain

0.97

D;D

M_CAP

Uncertain

0.096

MetaRNN

Uncertain

0.45

T;T

MetaSVM

Benign

-0.89

MutationAssessor

Uncertain

2.4

M;.

PrimateAI

Uncertain

0.76

PROVEAN

Pathogenic

-7.4

D;D

REVEL

Uncertain

0.41

Sift

Pathogenic

0.0

D;D

Sift4G

Pathogenic

0.0

D;D

Polyphen

0.98

D;.

Vest4

0.98

MVP

0.81

MPC

0.50

ClinPred

0.32

GERP RS

5.4

Varity_R

0.98

gMVP

0.91

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.020

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over