rs777842626

Positions:

• chr15-90782860-A-C
• chr15-90782860-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_000057.4(BLM):​c.2594A>C​(p.Tyr865Ser) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,436 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 3.63

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 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.077524126).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BLM	NM_000057.4	c.2594A>C	p.Tyr865Ser	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.2594A>C	p.Tyr865Ser	missense_variant	13/22	1	NM_000057.4	ENSP00000347232	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461436 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 727030

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Genetic Services Laboratory, University of Chicago

Aug 17, 2020

DNA sequence analysis of the BLM gene demonstrated a sequence change, c.2594A>C, in exon 13 that results in an amino acid change, p.Tyr865Ser. This sequence change does not appear to have been previously described in patients with BLM-related disorders and has also not been described in population databases (gnomAD, ExAC). The p.Tyr865Ser change affects a poorly conserved amino acid residue located in a domain of the BLM protein that is known to be functional. The p.Tyr865Ser substitution appears to be benign using several in-silico pathogenicity prediction tools (SIFT, PolyPhen2, Align GVGD, REVEL). Due to these contrasting evidences and the lack of functional studies, the clinical significance of the p.Tyr865Ser change remains unknown at this time. -

Bloom syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 06, 2022

This sequence change replaces tyrosine, which is neutral and polar, with serine, which is neutral and polar, at codon 865 of the BLM protein (p.Tyr865Ser). This variant is not present in population databases (gnomAD no frequency). 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: 1337698). 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

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 29, 2023

The p.Y865S variant (also known as c.2594A>C), located in coding exon 12 of the BLM gene, results from an A to C substitution at nucleotide position 2594. The tyrosine at codon 865 is replaced by serine, an amino acid with dissimilar 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	0.054
BayesDel_addAF	Benign	-0.21	T
BayesDel_noAF	Benign	-0.54
CADD	Benign	20
DANN	Benign	0.90
DEOGEN2	Benign	0.081	T;.
Eigen	Benign	-0.61
Eigen_PC	Benign	-0.29
FATHMM_MKL	Benign	0.70	D
LIST_S2	Benign	0.84	T;D
M_CAP	Benign	0.0063	T
MetaRNN	Benign	0.078	T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	-1.8	N;.
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.46	T
PROVEAN	Benign	1.3	N;N
REVEL	Benign	0.076
Sift	Benign	0.77	T;T
Sift4G	Benign	0.77	T;T
Polyphen		0.0020	B;.
Vest4		0.22
MutPred		0.45		Gain of disorder (P = 0.0099);Gain of disorder (P = 0.0099);
MVP		0.68
MPC		0.13
ClinPred		0.58	D
GERP RS		4.2
Varity_R		0.10
gMVP		0.77

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: rs777842626; hg19: chr15-91326090;