rs1555419944

chr15-90761064-A-Gchr15-90761064-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_000057.4(BLM):c.1691A>G(p.Asp564Gly) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D564V) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 3.93

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 Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.3803907).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.1691A>G	p.Asp564Gly	missense_variant	7/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.1691A>G	p.Asp564Gly	missense_variant	7/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:2

Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 22, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Aug 16, 2022	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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). ClinVar contains an entry for this variant (Variation ID: 524766). This variant has not been reported in the literature in individuals affected with BLM-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces aspartic acid, which is acidic and polar, with glycine, which is neutral and non-polar, at codon 564 of the BLM protein (p.Asp564Gly). -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 10, 2022

The p.D564G variant (also known as c.1691A>G), located in coding exon 6 of the BLM gene, results from an A to G substitution at nucleotide position 1691. The aspartic acid at codon 564 is replaced by glycine, an amino acid with similar properties. This amino acid position is conserved. 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	0.12
BayesDel_addAF	Benign	-0.056	T
BayesDel_noAF	Benign	-0.32
Cadd	Uncertain	24
Dann	Uncertain	1.0
DEOGEN2	Benign	0.13	T;.
Eigen	Uncertain	0.39
Eigen_PC	Uncertain	0.45
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Benign	0.85	D;D
M_CAP	Benign	0.010	T
MetaRNN	Benign	0.38	T;T
MetaSVM	Benign	-0.81	T
MutationAssessor	Uncertain	2.4	M;.
MutationTaster	Benign	0.88	D;D
PrimateAI	Benign	0.34	T
PROVEAN	Benign	-1.3	N;N
REVEL	Benign	0.11
Sift	Benign	0.21	T;T
Sift4G	Benign	0.39	T;T
Polyphen		1.0	D;.
Vest4		0.52
MutPred		0.38		Loss of disorder (P = 0.0666);Loss of disorder (P = 0.0666);
MVP		0.76
MPC		0.55
ClinPred		0.86	D
GERP RS		5.9
Varity_R		0.11
gMVP		0.57

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: rs1555419944; hg19: chr15-91304294;