rs1555422363

chr15-90782871-A-Cchr15-90782871-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_000057.4(BLM):c.2605A>C(p.Lys869Gln) 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 (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. K869E) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• 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]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.897

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.2605A>C	p.Lys869Gln	missense_variant	13/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.2605A>C	p.Lys869Gln	missense_variant	13/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Bloom syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Nov 07, 2017

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 missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with BLM-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces lysine with glutamine at codon 869 of the BLM protein (p.Lys869Gln). The lysine residue is highly conserved and there is a small physicochemical difference between lysine and glutamine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Uncertain	0.089	D
BayesDel_noAF	Benign	-0.11
Cadd	Pathogenic	26
Dann	Uncertain	1.0
DEOGEN2	Uncertain	0.54	D;.
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.91
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.97	D;D
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.90	D;D
MetaSVM	Uncertain	0.23	D
MutationAssessor	Pathogenic	3.5	M;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.61	T
PROVEAN	Uncertain	-3.7	D;D
REVEL	Uncertain	0.51
Sift	Uncertain	0.0030	D;D
Sift4G	Pathogenic	0.0	D;D
Polyphen		1.0	D;.
Vest4		0.75
MutPred		0.63		Loss of methylation at K869 (P = 0.0208);Loss of methylation at K869 (P = 0.0208);
MVP		0.91
MPC		0.50
ClinPred		1.0	D
GERP RS		5.5
Varity_R		0.69
gMVP		0.79

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

Other links and lift over

dbSNP: rs1555422363; hg19: chr15-91326101;