rs1555418283

Positions:

• chr15-90749497-C-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.229C>G​(p.Leu77Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 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 (★). Synonymous variant affecting the same amino acid position (i.e. L77L) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.634

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=0.09145436).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.229C>G	p.Leu77Val	missense_variant	3/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.229C>G	p.Leu77Val	missense_variant	3/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

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

Aug 31, 2021

This sequence change replaces leucine with valine at codon 77 of the BLM protein (p.Leu77Val). The leucine residue is weakly conserved and there is a small physicochemical difference between leucine and valine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with BLM-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.058
BayesDel_addAF	Benign	-0.23	T
BayesDel_noAF	Benign	-0.57
CADD	Benign	0.62
DANN	Benign	0.95
DEOGEN2	Benign	0.096	T;.
Eigen	Benign	-0.74
Eigen_PC	Benign	-0.85
FATHMM_MKL	Benign	0.033	N
LIST_S2	Benign	0.64	T;T
M_CAP	Benign	0.030	D
MetaRNN	Benign	0.091	T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Uncertain	2.2	M;.
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.20	T
PROVEAN	Benign	-0.43	N;N
REVEL	Benign	0.055
Sift	Benign	0.078	T;D
Sift4G	Benign	0.28	T;T
Polyphen		0.28	B;.
Vest4		0.081
MutPred		0.12		Gain of glycosylation at S74 (P = 0.0884);Gain of glycosylation at S74 (P = 0.0884);
MVP		0.71
MPC		0.10
ClinPred		0.071	T
GERP RS		-0.46
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.029
gMVP		0.033

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: rs1555418283; hg19: chr15-91292727;