rs1291378382

Positions:

• chr15-90749392-T-C

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_000057.4(BLM):​c.124T>C​(p.Ser42Pro) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000482 in 1,452,842 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000048 (0 hom.)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: -0.619

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 Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.06215927).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BLM	NM_000057.4	c.124T>C	p.Ser42Pro	missense_variant	3/22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.124T>C	p.Ser42Pro	missense_variant	3/22	1	NM_000057.4	ENSP00000347232	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000201 AC: 5 AN: 248932 Hom.: 0 AF XY: 0.0000296 AC XY: 4 AN XY: 135100

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000146

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000482 AC: 7 AN: 1452842 Hom.: 0 Cov.: 31 AF XY: 0.00000830 AC XY: 6 AN XY: 723224

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.000158

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.0000113

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:2

Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Oct 24, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 22, 2023	This sequence change replaces serine, which is neutral and polar, with proline, which is neutral and non-polar, at codon 42 of the BLM protein (p.Ser42Pro). This variant is present in population databases (no rsID available, gnomAD 0.02%). 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: 485327). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Not Available"; PolyPhen-2: "Benign"; Align-GVGD: "Not Available". The proline amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. 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. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Oct 21, 2022

The variant has not been reported in the published literature. The frequency of this variant in the general population, 0.00015 (5/34214 chromosomes, http://gnomad.broadinstitute.org), is uninformative in assessment of its pathogenicity. Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded predictions that this variant is benign. Based on the available information, we are unable to determine the clinical significance of this variant. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 14, 2023

The p.S42P variant (also known as c.124T>C), located in coding exon 2 of the BLM gene, results from a T to C substitution at nucleotide position 124. The serine at codon 42 is replaced by proline, 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	0.066
BayesDel_addAF	Benign	-0.42	T
BayesDel_noAF	Benign	-0.58
CADD	Benign	2.9
DANN	Benign	0.93
DEOGEN2	Benign	0.050	T;.
Eigen	Benign	-1.2
Eigen_PC	Benign	-1.2
FATHMM_MKL	Benign	0.019	N
LIST_S2	Benign	0.54	T;T
M_CAP	Benign	0.012	T
MetaRNN	Benign	0.062	T;T
MetaSVM	Benign	-1.1	T
MutationAssessor	Benign	0.045	N;.
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.30	T
PROVEAN	Benign	-0.35	N;N
REVEL	Benign	0.037
Sift	Benign	0.23	T;T
Sift4G	Benign	0.37	T;T
Polyphen		0.0	B;.
Vest4		0.13
MutPred		0.17		Loss of phosphorylation at S42 (P = 0.0373);Loss of phosphorylation at S42 (P = 0.0373);
MVP		0.54
MPC		0.11
ClinPred		0.015	T
GERP RS		-3.0
Varity_R		0.090
gMVP		0.035

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: rs1291378382; hg19: chr15-91292622;