15-90769187-C-G

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_000057.4(BLM):c.2362C>G(p.Leu788Val) 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 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. L788I) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 3.15

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 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.757

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.2362C>G	p.Leu788Val	missense_variant	11/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.2362C>G	p.Leu788Val	missense_variant	11/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Jan 24, 2023	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. 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) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on BLM protein function. ClinVar contains an entry for this variant (Variation ID: 584889). This variant has not been reported in the literature in individuals affected with BLM-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces leucine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 788 of the BLM protein (p.Leu788Val). -
Uncertain significance, criteria provided, single submitter	clinical testing	Mendelics	Jul 02, 2018	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.20
BayesDel_addAF	Uncertain	0.064	T
BayesDel_noAF	Benign	-0.15
Cadd	Pathogenic	26
Dann	Uncertain	1.0
DEOGEN2	Benign	0.17	T;.
Eigen	Uncertain	0.57
Eigen_PC	Uncertain	0.56
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.92	D;D
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.76	D;D
MetaSVM	Uncertain	-0.16	T
MutationAssessor	Benign	1.8	L;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.49	T
PROVEAN	Uncertain	-2.7	D;D
REVEL	Uncertain	0.46
Sift	Uncertain	0.0090	D;D
Sift4G	Uncertain	0.022	D;D
Polyphen		0.98	D;.
Vest4		0.65
MutPred		0.55		Gain of sheet (P = 0.0827);Gain of sheet (P = 0.0827);
MVP		0.88
MPC		0.46
ClinPred		0.94	D
GERP RS		4.4
Varity_R		0.80
gMVP		0.75

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: rs149754073; hg19: chr15-91312417;