chr15-90751792-A-G

Position:

• chr15-90751792-A-G

Variant summary

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

The NM_001287248.2(BLM):​c.-487A>G variant causes a 5 prime UTR premature start codon gain change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000206 in 1,458,874 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: BLM NM_001287248.2 5_prime_UTR_premature_start_codon_gain
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 0.308

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]

BLM (HGNC:):

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=0.050448418).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BLM	NM_000057.4	c.805A>G	p.Ser269Gly	missense_variant	4/22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.805A>G	p.Ser269Gly	missense_variant	4/22	1	NM_000057.4	ENSP00000347232.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000797 AC: 2 AN: 251070 Hom.: 0 AF XY: 0.00000737 AC XY: 1 AN XY: 135732

Gnomad AFR exome AF: 0.0000616

Gnomad AMR exome AF: 0.00

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: 0.00000881

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000206 AC: 3 AN: 1458874 Hom.: 0 Cov.: 30 AF XY: 0.00000275 AC XY: 2 AN XY: 725994

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: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000371 Hom.: 0

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.00000824 AC: 1

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.	May 07, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 20, 2023	This sequence change replaces serine, which is neutral and polar, with glycine, which is neutral and non-polar, at codon 269 of the BLM protein (p.Ser269Gly). This variant is present in population databases (rs141411463, gnomAD 0.007%). 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: 405275). 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 glycine 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

Jan 31, 2024

The BLM c.805A>G (p.Ser269Gly) variant has not been reported in individuals with BLM-related conditions in the published literature. The frequency of this variant in the general population, 0.000008 (2/251070 chromosomes (Genome Aggregation Database, http://gnomad.broadinstitute.org)), is uninformative in the 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

Jun 22, 2024

The c.805A>G (p.S269G) alteration is located in exon 4 (coding exon 3) of the BLM gene. This alteration results from a A to G substitution at nucleotide position 805, causing the serine (S) at amino acid position 269 to be replaced by a glycine (G). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.057
BayesDel_addAF	Benign	-0.40	T
BayesDel_noAF	Benign	-0.63
CADD	Benign	7.8
DANN	Benign	0.96
DEOGEN2	Benign	0.057	T;.
Eigen	Benign	-0.99
Eigen_PC	Benign	-0.94
FATHMM_MKL	Benign	0.072	N
LIST_S2	Benign	0.52	T;T
M_CAP	Benign	0.0061	T
MetaRNN	Benign	0.050	T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	1.2	L;.
PrimateAI	Benign	0.23	T
PROVEAN	Benign	-0.96	N;N
REVEL	Benign	0.060
Sift	Benign	0.19	T;T
Sift4G	Benign	0.49	T;T
Polyphen		0.0	B;.
Vest4		0.070
MVP		0.55
MPC		0.081
ClinPred		0.022	T
GERP RS		0.80
Varity_R		0.029
gMVP		0.043

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: rs141411463; hg19: chr15-91295022;