rs1555422355

Positions:

• chr15-90782838-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_000057.4(BLM):​c.2572A>G​(p.Asn858Asp) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 8.84

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 (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.785

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BLM	NM_000057.4	c.2572A>G	p.Asn858Asp	missense_variant	13/22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.2572A>G	p.Asn858Asp	missense_variant	13/22	1	NM_000057.4	ENSP00000347232.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

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.	Aug 07, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Apr 12, 2017	In summary, this variant is a novel missense change with uncertain impact on protein function. It has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a BLM-related disease. This sequence change replaces asparagine with aspartic acid at codon 858 of the BLM protein (p.Asn858Asp). The asparagine residue is highly conserved and there is a small physicochemical difference between asparagine and aspartic acid. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jun 29, 2023

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.57
BayesDel_addAF	Uncertain	0.030	T
BayesDel_noAF	Benign	-0.19
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.53	D;.
Eigen	Uncertain	0.32
Eigen_PC	Uncertain	0.44
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.93	D;D
M_CAP	Benign	0.072	D
MetaRNN	Pathogenic	0.78	D;D
MetaSVM	Benign	-0.63	T
MutationAssessor	Benign	1.2	L;.
PrimateAI	Uncertain	0.69	T
PROVEAN	Pathogenic	-4.4	D;D
REVEL	Uncertain	0.48
Sift	Uncertain	0.017	D;D
Sift4G	Pathogenic	0.0	D;T
Polyphen		0.62	P;.
Vest4		0.84
MutPred		0.54		Gain of catalytic residue at N858 (P = 0.0331);Gain of catalytic residue at N858 (P = 0.0331);
MVP		0.86
MPC		0.47
ClinPred		0.99	D
GERP RS		5.5
Varity_R		0.86
gMVP		0.79

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: rs1555422355; hg19: chr15-91326068;