rs775005766

Positions:

Variant summary

Our verdict is Benign. Variant got -8 ACMG points: 0P and 8B. BP4_StrongBS2

The NM_000057.4(BLM):c.887A>G(p.Tyr296Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000347 in 1,612,962 control chromosomes in the GnomAD database, including 2 homozygotes. In-silico tool predicts a benign outcome for this variant. 14/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. Y296F) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000037 ( 2 hom. )

Consequence

BLM
NM_000057.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3B:1

Conservation

PhyloP100: 0.235

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 Benign. Variant got -8 ACMG points.

BP4

Computational evidence support a benign effect (MetaRNN=0.038859308).

BS2

High Homozygotes in GnomAdExome4 at 2 AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4 linkuse as main transcript	c.887A>G	p.Tyr296Cys	missense_variant	4/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8 linkuse as main transcript	c.887A>G	p.Tyr296Cys	missense_variant	4/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes

AF:

0.0000131

AC:

AN:

152230

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.000414

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000836

AC:

AN:

251272

Hom.:

AF XY:

0.000125

AC XY:

AN XY:

135816

show subpopulations

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 SAS exome

AF:

0.000686

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000370

AC:

AN:

1460614

Hom.:

Cov.:

AF XY:

0.0000537

AC XY:

AN XY:

726678

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.000603

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000180

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000131

AC:

AN:

152348

Hom.:

Cov.:

AF XY:

0.0000268

AC XY:

AN XY:

74512

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.000414

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

ExAC

AF:

0.000115

AC:

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3Benign:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not specified

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Genetic Services Laboratory, University of Chicago

May 03, 2021

DNA sequence analysis of the BLM gene demonstrated a sequence change, c.887A>G, in exon 4 that results in an amino acid change, p.Tyr296Cys. This sequence change has been described in gnomAD with a frequency of 0.069% in the South Asian sub-population (dbSNP rs775005766). The p.Tyr296Cys change affects a poorly conserved amino acid residue located in a domain of the BLM protein that is not known to be functional. The p.Tyr296Cys substitution appears to be benign using several in-silico pathogenicity prediction tools (SIFT, PolyPhen2, Align GVGD, REVEL). This sequence change does not appear to have been previously described in patients with BLM-related disorders. Due to the lack of sufficient evidences, the clinical significance of the p.Tyr296Cys change remains unknown at this time. -

Bloom syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Oct 21, 2022

This sequence change replaces tyrosine, which is neutral and polar, with cysteine, which is neutral and slightly polar, at codon 296 of the BLM protein (p.Tyr296Cys). This variant is present in population databases (rs775005766, gnomAD 0.07%). 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: 405307). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt BLM protein function. 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. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Oct 27, 2022

To the best of our knowledge, the variant has not been reported in the published literature. The frequency of this variant in the general population, 0.00069 (21/30608 chromosomes in South Asian subpopulation, 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 benign. Based on the available information, we are unable to determine the clinical significance of this variant. -

Hereditary cancer-predisposing syndrome

Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 28, 2022

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. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.075

BayesDel_addAF

Benign

-0.38

BayesDel_noAF

Benign

-0.41

CADD

Benign

DANN

Uncertain

0.99

DEOGEN2

Benign

0.11

T;.

Eigen

Benign

-0.65

Eigen_PC

Benign

-0.66

FATHMM_MKL

Benign

0.30

LIST_S2

Benign

0.82

T;T

M_CAP

Benign

0.013

MetaRNN

Benign

0.039

T;T

MetaSVM

Benign

-1.0

MutationAssessor

Uncertain

2.4

M;.

MutationTaster

Benign

1.0

N;N

PrimateAI

Benign

0.43

PROVEAN

Benign

-1.8

N;N

REVEL

Benign

0.027

Sift

Benign

0.17

T;T

Sift4G

Benign

0.18

T;T

Polyphen

0.025

B;.

Vest4

0.30

MutPred

0.28

Loss of phosphorylation at Y296 (P = 0.0046);Loss of phosphorylation at Y296 (P = 0.0046);

MVP

0.78

MPC

0.11

ClinPred

0.064

GERP RS

0.047

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.1

Varity_R

0.052

gMVP

0.082

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

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