rs878853555

chr15-90749968-G-A

Variant summary

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

The NM_000057.4(BLM):c.700G>A(p.Asp234Asn) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000018 in 1,614,096 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 (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D234E) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000018 (0 hom.)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.485

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=0.09770462).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.700G>A	p.Asp234Asn	missense_variant	3/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.700G>A	p.Asp234Asn	missense_variant	3/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152218 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000207

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.0000185 AC: 27 AN: 1461878 Hom.: 0 Cov.: 31 AF XY: 0.0000179 AC XY: 13 AN XY: 727238

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000225

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152218 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74358

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.000207

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Jan 20, 2024	This sequence change replaces aspartic acid, which is acidic and polar, with asparagine, which is neutral and polar, at codon 234 of the BLM protein (p.Asp234Asn). This variant is present in population databases (no rsID available, gnomAD 0.01%). 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: 236824). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be tolerated. 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. -
Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Nov 06, 2018	- -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Apr 04, 2022

The p.D234N variant (also known as c.700G>A), located in coding exon 2 of the BLM gene, results from a G to A substitution at nucleotide position 700. The aspartic acid at codon 234 is replaced by asparagine, an amino acid with highly similar 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	0.074
BayesDel_addAF	Benign	-0.29	T
BayesDel_noAF	Benign	-0.66
Cadd	Benign	20
Dann	Uncertain	1.0
DEOGEN2	Benign	0.065	T;.
Eigen	Benign	-0.52
Eigen_PC	Benign	-0.52
FATHMM_MKL	Benign	0.080	N
LIST_S2	Benign	0.66	T;T
M_CAP	Benign	0.013	T
MetaRNN	Benign	0.098	T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Uncertain	2.2	M;.
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.30	T
PROVEAN	Benign	-0.99	N;N
REVEL	Benign	0.097
Sift	Benign	0.11	T;D
Sift4G	Benign	0.37	T;T
Polyphen		0.49	P;.
Vest4		0.11
MutPred		0.21		Gain of sheet (P = 0.0028);Gain of sheet (P = 0.0028);
MVP		0.77
MPC		0.13
ClinPred		0.22	T
GERP RS		1.7
Varity_R		0.054
gMVP		0.16

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: rs878853555; hg19: chr15-91293198;