rs1555424403

Positions:

• chr15-90804341-A-T

Variant summary

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

The NM_000057.4(BLM):​c.3733A>T​(p.Thr1245Ser) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts 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. T1245T) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.61

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=0.38666588).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.3733A>T	p.Thr1245Ser	missense_variant	19/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.3733A>T	p.Thr1245Ser	missense_variant	19/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

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

Labcorp Genetics (formerly Invitae), Labcorp

Jan 12, 2017

This sequence change replaces threonine with serine at codon 1245 of the BLM protein (p.Thr1245Ser). The threonine residue is moderately conserved and there is a small physicochemical difference between threonine and serine. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a BLM-related disease. Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). In summary, this variant is a novel missense change with uncertain impact on protein function. It has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.38
BayesDel_addAF	Pathogenic	0.21	D
BayesDel_noAF	Uncertain	0.070
CADD	Benign	23
DANN	Uncertain	1.0
DEOGEN2	Benign	0.19	T
Eigen	Uncertain	0.26
Eigen_PC	Uncertain	0.36
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Benign	0.79	T
M_CAP	Benign	0.030	D
MetaRNN	Benign	0.39	T
MetaSVM	Benign	-0.82	T
MutationAssessor	Uncertain	2.3	M
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.68	T
PROVEAN	Benign	-2.3	N
REVEL	Benign	0.22
Sift	Uncertain	0.020	D
Sift4G	Uncertain	0.046	D
Polyphen		0.27	B
Vest4		0.47
MutPred		0.60		Loss of helix (P = 0.0104);
MVP		0.85
MPC		0.42
ClinPred		0.96	D
GERP RS		5.9
Varity_R		0.59
gMVP		0.57

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs1555424403; hg19: chr15-91347571;