15-90749636-A-G

Position:

chr15-90749636-A-G

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2BP4_Strong

The NM_000057.4(BLM):c.368A>G(p.Gln123Arg) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000204 in 1,614,060 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.000046 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000018 ( 0 hom. )

Consequence

BLM
NM_000057.4 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:7

Conservation

PhyloP100: -0.879

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:

BLM (HGNC:):

BLM links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Likely_benign. Variant got -2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.05027339).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BLM	NM_000057.4 linkuse as main transcript	c.368A>G	p.Gln123Arg	missense_variant	3/22	ENST00000355112.8	NP_000048.1	P54132

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8 linkuse as main transcript	c.368A>G	p.Gln123Arg	missense_variant	3/22	1	NM_000057.4	ENSP00000347232.3		P54132

Frequencies

GnomAD3 genomes

AF:

0.0000460

AC:

AN:

152200

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000241

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000655

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000735

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000318

AC:

AN:

251252

Hom.:

AF XY:

0.0000442

AC XY:

AN XY:

135836

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000289

Gnomad ASJ exome

AF:

0.0000993

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000528

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000178

AC:

AN:

1461860

Hom.:

Cov.:

AF XY:

0.0000124

AC XY:

AN XY:

727234

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.0000224

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.0000198

Gnomad4 OTH exome

AF:

0.0000497

GnomAD4 genome

AF:

0.0000460

AC:

AN:

152200

Hom.:

Cov.:

AF XY:

0.0000672

AC XY:

AN XY:

74358

show subpopulations

Gnomad4 AFR

AF:

0.0000241

Gnomad4 AMR

AF:

0.0000655

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000735

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000712

Hom.:

Bravo

AF:

0.0000340

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000116

AC:

ExAC

AF:

0.0000330

AC:

EpiCase

AF:

0.00

EpiControl

AF:

0.000119

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:7

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Bloom syndrome

Uncertain:3

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	Oct 23, 2022	This sequence change replaces glutamine, which is neutral and polar, with arginine, which is basic and polar, at codon 123 of the BLM protein (p.Gln123Arg). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This missense change has been observed in individual(s) with prostate cancer (PMID: 25111073). ClinVar contains an entry for this variant (Variation ID: 127503). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The arginine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect 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:2

Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Mar 03, 2014	Single mutation in BLM have only recently been described in association with cancer predisposition and the risks are not well understood. This variant is denoted BLM c.368A>G at the cDNA level, p.Gln123Arg (Q123R) at the protein level, and results in the change of a Glutamine to an Arginine (CAA>CGA). This variant has not, to our knowledge, been published in the literature as pathogenic or benign. BLM Gln123Arg was not observed at a significant allele frequency in the NHLBI Exome Sequencing Project. Since Glutamine and Arginine differ in some properties, this is considered a semi-conservative amino acid substitution and may affect protein integrity. BLM Gln123Arg occurs at a position that is moderately conserved across species and is not located in a known functional domain. In silico analyses predict that this variant is unlikely to alter protein structure or function. On a molecular level, the impact of this missense variant on protein structure and function is not known and thus we consider this to be a variant of uncertain significance. Furthermore, based on the currently available information, cancer risks associated with this variant, and with single variants the BLM gene in general, remain unclear. -
Uncertain significance, criteria provided, single submitter	clinical testing	Institute for Clinical Genetics, University Hospital TU Dresden, University Hospital TU Dresden	Nov 03, 2021	- -

not specified

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Oct 14, 2024

Variant summary: BLM c.368A>G (p.Gln123Arg) results in a conservative amino acid change in the encoded protein sequence. Five of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 3.2e-05 in 251252 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.368A>G has been reported in the literature in individuals affected with Cancer (Johnson_2014). These report(s) do not provide unequivocal conclusions about association of the variant with Bloom Syndrome. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publication have been ascertained in the context of this evaluation (PMID: 25111073). ClinVar contains an entry for this variant (Variation ID: 127503). Based on the evidence outlined above, the variant was classified as uncertain significance. -

Hereditary cancer-predisposing syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 14, 2023

The p.Q123R variant (also known as c.368A>G), located in coding exon 2 of the BLM gene, results from an A to G substitution at nucleotide position 368. The glutamine at codon 123 is replaced by arginine, an amino acid with highly similar properties. This variant segregated with disease in three individuals from a familial prostate cancer family; however, three variants in other genes also co-segregated with prostate cancer in this family (Johnson AM et al. Prostate 2014 Oct;74(14):1371-8). This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.069

BayesDel_addAF

Benign

-0.44

BayesDel_noAF

Benign

-0.71

CADD

Benign

0.051

DANN

Benign

0.53

DEOGEN2

Benign

0.057

T;.

Eigen

Benign

-1.2

Eigen_PC

Benign

-1.3

FATHMM_MKL

Benign

0.023

LIST_S2

Benign

0.55

T;T

M_CAP

Benign

0.017

MetaRNN

Benign

0.050

T;T

MetaSVM

Benign

-0.98

MutationAssessor

Benign

1.1

L;.

PrimateAI

Benign

0.21

PROVEAN

Benign

-0.64

N;N

REVEL

Benign

0.027

Sift

Benign

0.87

T;T

Sift4G

Benign

0.56

T;T

Polyphen

0.0010

B;.

Vest4

0.062

MVP

0.52

MPC

0.095

ClinPred

0.024

GERP RS

-2.3

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.1

Varity_R

0.089

gMVP

0.11

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.010

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