15-90763017-A-T

Variant names:

• chr15-90763017-A-T
• rs377563699
• NM_000057.4:c.1934A>T

Variant summary

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

The NM_000057.4(BLM):​c.1934A>T​(p.Gln645Leu) variant causes a missense change. The variant allele was found at a frequency of 0.0000263 in 152,218 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 0.000026 (0 hom., cov: 32)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 4.63

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=0.29988825).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BLM	NM_000057.4	c.1934A>T	p.Gln645Leu	missense_variant	Exon 8 of 22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.1934A>T	p.Gln645Leu	missense_variant	Exon 8 of 22	1	NM_000057.4	ENSP00000347232.3

Frequencies

GnomAD3 genomes AF: 0.0000263 AC: 4 AN: 152218 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000965

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

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: 0.00000399 AC: 1 AN: 250372 Hom.: 0 AF XY: 0.00000739 AC XY: 1 AN XY: 135324

Gnomad AFR exome AF: 0.0000619

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome Cov.: 31

GnomAD4 genome AF: 0.0000263 AC: 4 AN: 152218 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74376

Gnomad4 AFR AF: 0.0000965

Gnomad4 AMR AF: 0.00

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

Bravo AF: 0.0000151

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:1

Sep 27, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamine, which is neutral and polar, with leucine, which is neutral and non-polar, at codon 645 of the BLM protein (p.Gln645Leu). This variant is present in population databases (rs377563699, gnomAD 0.008%). This variant has not been reported in the literature in individuals affected with BLM-related conditions. ClinVar contains an entry for this variant (Variation ID: 660272). 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. 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. -

Hereditary cancer-predisposing syndrome Uncertain:1

May 25, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.Q645L variant (also known as c.1934A>T), located in coding exon 7 of the BLM gene, results from an A to T substitution at nucleotide position 1934. The glutamine at codon 645 is replaced by leucine, an amino acid with dissimilar properties. 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	0.10
BayesDel_addAF	Benign	-0.093	T
BayesDel_noAF	Benign	-0.19
CADD	Benign	21
DANN	Uncertain	0.99
DEOGEN2	Benign	0.24	T;.
Eigen	Benign	0.00038
Eigen_PC	Benign	0.17
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.77	T;T
M_CAP	Benign	0.072	D
MetaRNN	Benign	0.30	T;T
MetaSVM	Benign	-0.39	T
MutationAssessor	Benign	1.9	M;.
PrimateAI	Benign	0.33	T
PROVEAN	Uncertain	-3.7	D;D
REVEL	Benign	0.25
Sift	Benign	0.056	T;D
Sift4G	Benign	0.23	T;T
Polyphen		0.0010	B;.
Vest4		0.31
MutPred		0.31		Loss of disorder (P = 0.0438);Loss of disorder (P = 0.0438);
MVP		0.87
MPC		0.12
ClinPred		0.31	T
GERP RS		5.5
Varity_R		0.25
gMVP		0.54

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.060		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: rs377563699; hg19: chr15-91306247;