rs1060500649

chr15-90815113-C-T

Variant summary

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

The NM_000057.4(BLM):c.4088C>T(p.Thr1363Ile) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000186 in 1,613,944 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/21 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. T1363A) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 0.662

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]

(HGNC:):

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=0.15453136).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4	c.4088C>T	p.Thr1363Ile	missense_variant	22/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8	c.4088C>T	p.Thr1363Ile	missense_variant	22/22	1	NM_000057.4	P2
	ENST00000656405.1	n.432G>A		non_coding_transcript_exon_variant	1/2

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152134 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461810 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727214

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: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152134 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74326

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000147

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Oct 24, 2016

In summary, this variant is a novel missense change that is not predicted to affect protein function. There is no indication that it causes disease, but the available evidence is currently insufficient to prove that conclusively. Therefore, it has been classified as a Variant of Uncertain Significance. 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, but these predictions have not been confirmed by published functional studies. 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. This sequence change replaces threonine with isoleucine at codon 1363 of the BLM protein (p.Thr1363Ile). The threonine residue is weakly conserved and there is a moderate physicochemical difference between threonine and isoleucine. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 30, 2020

The p.T1363I variant (also known as c.4088C>T), located in coding exon 21 of the BLM gene, results from a C to T substitution at nucleotide position 4088. The threonine at codon 1363 is replaced by isoleucine, an amino acid with 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	0.097
BayesDel_addAF	Benign	-0.11	T
BayesDel_noAF	Benign	-0.40
Cadd	Benign	8.3
Dann	Benign	0.94
DEOGEN2	Benign	0.23	T;.
Eigen	Benign	-0.51
Eigen_PC	Benign	-0.51
FATHMM_MKL	Benign	0.13	N
LIST_S2	Benign	0.70	T;T
M_CAP	Benign	0.016	T
MetaRNN	Benign	0.15	T;T
MetaSVM	Benign	-0.97	T
MutationAssessor	Uncertain	2.2	M;.
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.28	T
PROVEAN	Benign	-2.1	N;N
REVEL	Benign	0.11
Sift	Uncertain	0.020	D;D
Sift4G	Benign	0.19	T;T
Polyphen		0.041	B;.
Vest4		0.18
MutPred		0.22		Loss of phosphorylation at T1363 (P = 0.0131);.;
MVP		0.83
MPC		0.11
ClinPred		0.24	T
GERP RS		5.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0
Varity_R		0.063
gMVP		0.30

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: rs1060500649; hg19: chr15-91358343;