rs748943489

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2BP4_Moderate

The NM_000057.4(BLM):c.3970C>T(p.His1324Tyr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000929 in 1,614,048 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000096 ( 0 hom. )

Consequence

BLM
NM_000057.4 missense

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:5

Conservation

PhyloP100: 1.66

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 0 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (MetaRNN=0.24489972).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4 linkuse as main transcript	c.3970C>T	p.His1324Tyr	missense_variant	21/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8 linkuse as main transcript	c.3970C>T	p.His1324Tyr	missense_variant	21/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152166

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

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:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000239

AC:

AN:

251442

Hom.:

AF XY:

0.0000147

AC XY:

AN XY:

135896

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:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000528

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000958

AC:

AN:

1461882

Hom.:

Cov.:

AF XY:

0.00000963

AC XY:

AN XY:

727242

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:

0.0000116

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000989

Gnomad4 OTH exome

AF:

0.0000331

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152166

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74332

show subpopulations

Gnomad4 AFR

AF:

0.00

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:

0.00

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000959

Hom.:

Bravo

AF:

0.00000378

ExAC

AF:

0.0000165

AC:

EpiCase

AF:

0.000109

EpiControl

AF:

0.000119

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Bloom syndrome

Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Oct 22, 2022	This sequence change replaces histidine, which is basic and polar, with tyrosine, which is neutral and polar, at codon 1324 of the BLM protein (p.His1324Tyr). This variant is present in population databases (rs748943489, gnomAD 0.004%). This missense change has been observed in individual(s) with clinical features of Bloom syndrome (PMID: 17407155, 31159747). ClinVar contains an entry for this variant (Variation ID: 454145). 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. Experimental studies have shown that this missense change does not substantially affect BLM function (PMID: 17407155). 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. -
Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -

Hereditary cancer-predisposing syndrome

Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	GeneKor MSA	Aug 01, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Dec 01, 2022	The p.H1324Y variant (also known as c.3970C>T), located in coding exon 20 of the BLM gene, results from a C to T substitution at nucleotide position 3970. The histidine at codon 1324 is replaced by tyrosine, an amino acid with similar properties. This variant has been identified in one person with Bloom Syndrome and functional studies have shown that it preserves normal BLM protein function in reducing the levels of sister-chromatid exchanges in patient-derived cells (German J et al. Hum. Mutat., 2007 Aug;28:743-53; Perreault-Micale C et al. Mol Genet Genomic Med, 2015 Jul;3:363-73). Another study determined that this variant (reported as c.3970C>T, p.H1324T) was not sensitive to the DNA damaging agent, hydroxyurea, similar to wildtype (Mirzaei H et al. Proc. Natl. Acad. Sci. U.S.A., 2012 Nov;109:19357-62). This variant was also reported as a variant of unknown signifcance in 1/1197 individuals from Greece, Romania, and Turkey undergoing evaluation for inherited cancer predisposition (Tsaousis GN et al. BMC Cancer, 2019 Jun;19:535). This amino acid position is 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. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Feb 28, 2022

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; Observed in an individual undergoing genetic testing for hereditary cancer predisposition and in an individual with Bloom syndrome in published literature (German 2007, Tsaousis 2019); Published functional studies suggest no damaging effect: reduced levels of sister-chromatid exchanges (German 2007); This variant is associated with the following publications: (PMID: 26247052, 31159747, 17407155) -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.075

BayesDel_addAF

Benign

-0.16

BayesDel_noAF

Benign

-0.34

Cadd

Benign

Dann

Uncertain

0.97

DEOGEN2

Benign

0.23

T;.

Eigen

Benign

0.0054

Eigen_PC

Benign

0.14

FATHMM_MKL

Uncertain

0.79

LIST_S2

Benign

0.78

T;T

M_CAP

Benign

0.0061

MetaRNN

Benign

0.24

T;T

MetaSVM

Benign

-1.0

MutationAssessor

Uncertain

2.4

M;.

MutationTaster

Benign

0.96

N;N

PrimateAI

Benign

0.47

PROVEAN

Benign

-1.5

N;N

REVEL

Benign

0.12

Sift

Benign

0.34

T;T

Sift4G

Benign

0.82

T;T

Polyphen

0.031

B;.

Vest4

0.28

MutPred

0.27

Gain of sheet (P = 0.0043);.;

MVP

0.84

MPC

0.32

ClinPred

0.33

GERP RS

5.9

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.12

gMVP

0.21

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