NM_000057.4:c.98+1G>C

Variant names:

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_ModeratePM2PP5_Very_Strong

The NM_000057.4(BLM):c.98+1G>C variant causes a splice donor, intron change. The variant allele was found at a frequency of 0.0000138 in 1,591,844 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 31)

Exomes 𝑓: 0.000015 ( 0 hom. )

Consequence

BLM
NM_000057.4 splice_donor, intron

Scores

Splicing: ADA: 1.000

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:9

Conservation

PhyloP100: 5.17

Variant links:

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 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 12 ACMG points.

PVS1

Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.023977432 fraction of the gene. No cryptic splice site detected. Exon removal is inframe change.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 15-90747491-G-C is Pathogenic according to our data. Variant chr15-90747491-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 667391.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BLM	NM_000057.4 link	c.98+1G>C		splice_donor_variant, intron_variant	Intron 2 of 21	ENST00000355112.8	NP_000048.1	P54132

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8 link	c.98+1G>C		splice_donor_variant, intron_variant	Intron 2 of 21	1	NM_000057.4	ENSP00000347232.3		P54132

Frequencies

GnomAD3 genomes

AF:

0.00000658

AC:

AN:

152076

Hom.:

Cov.:

show subpopulations

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

GnomAD3 exomes

AF:

0.0000260

AC:

AN:

230636

Hom.:

AF XY:

0.0000402

AC XY:

AN XY:

124262

show subpopulations

Gnomad AFR exome

AF:

0.00

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:

0.0000599

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000146

AC:

AN:

1439768

Hom.:

Cov.:

AF XY:

0.0000196

AC XY:

AN XY:

715722

show subpopulations

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:

0.0000183

Gnomad4 OTH exome

AF:

0.0000168

GnomAD4 genome

AF:

0.00000658

AC:

AN:

152076

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74278

show subpopulations

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

Alfa

AF:

0.0000564

Hom.:

Bravo

AF:

0.00000756

ExAC

AF:

0.0000412

AC:

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:9

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Bloom syndrome

Pathogenic:5

Sep 27, 2023

Institute of Human Genetics, University of Leipzig Medical Center

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Criteria applied: PVS1_MOD,PP1_MOD,PS1_SUP,PM2_SUP -

Jul 18, 2018

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.98+1G>C variant in BLM has not been reported individuals with Bloom syndro me, but another variant at the same nucleotide position (c.98+1G>T) has been rep orted in the compound heterozygous state in 1 individual with Bloom syndrome (Ge rman 2007). A third variant at this nucleotide position (c.98+1G>A) has been rep orted to segregate with cancer risk in a single pedigree (de Voer 2015). This va riant has been identified in 7/113042 European chromosomes by the Genome Aggrega tion Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs750293380). Thi s variant occurs in the invariant region (+/- 1/2) of the splice consensus seque nce and is predicted to cause altered splicing leading to an abnormal or absent protein. Loss of function of the BLM gene is an established disease mechanism in autosomal recessive Bloom syndrome. In summary, the c.98+1G>C variant meets cri teria to be classified as pathogenic for Bloom syndrome in an autosomal recessiv e manner. ACMG/AMP criteria applied: PVS1_Strong, PM5, PM2 -

Feb 28, 2024

Baylor Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dec 24, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects a donor splice site in intron 2 of the BLM gene. RNA analysis indicates that disruption of this splice site induces altered splicing and may result in an absent or altered protein product. This variant is present in population databases (rs750293380, gnomAD 0.006%). Disruption of this splice site has been observed in individual(s) with Bloom syndrome, colorectal cancer, endometrial cancer, and/or prostate cancer (PMID: 17407155, 26358404, 26689913, 29439820). ClinVar contains an entry for this variant (Variation ID: 667391). Studies have shown that disruption of this splice site results in exon 2 skipping and activation of a cryptic splice site, and produces a non-functional protein and/or introduces a premature termination codon (internal data). For these reasons, this variant has been classified as Pathogenic. -

Apr 12, 2022

Fulgent Genetics, Fulgent Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided

Pathogenic:2

Nov 09, 2022

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Canonical splice site variant predicted to result in a null allele in a gene for which loss-of-function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); Observed in individuals with colorectal cancer, male breast cancer, ovarian cancer, and endometrial cancer (de Voer 2015, Lu 2015, Koczkowska 2018, Rizzolo 2019); This variant is associated with the following publications: (PMID: 26689913, 26358404, 30441849, 30613976) -

Nov 03, 2021

Institute for Clinical Genetics, University Hospital TU Dresden, University Hospital TU Dresden

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

BLM-related disorder

Pathogenic:1

Jun 12, 2024

PreventionGenetics, part of Exact Sciences

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

The BLM c.98+1G>C variant is predicted to disrupt the GT donor site and interfere with normal splicing. To our knowledge, this variant has not been reported in the literature in BLM associated disorders. This variant is reported in 0.0061% of alleles in individuals of European (Non-Finnish) descent in gnomAD. This variant is interpreted as likely pathogenic or pathogenic in ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/variation/667391/). Variants that disrupt the consensus splice donor site in BLM are expected to be pathogenic. This variant is interpreted as likely pathogenic. -

Hereditary cancer-predisposing syndrome

Pathogenic:1

Jan 11, 2024

Ambry Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.98+1G>C intronic variant results from a G to C substitution one nucleotide after coding exon 1 of the BLM gene. This nucleotide position is highly conserved in available vertebrate species. Another alteration at this position (c.98+1G>T) has been reported in a compound heterozygous state in an individual with Bloom syndrome (German J et al. Hum. Mutat. 2007 Aug;28(8):743-53). Additionally, another alteration at this position (c.98+1G>A) has been reported in a heterozygous state in an individual with a personal history of early-onset colorectal cancer and a strong family history of colorectal cancer (deVoer RM et al. Sci. Rep. 2015 Sep;5:14060). In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. As such, this alteration is classified as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.50

BayesDel_noAF

Pathogenic

0.26

CADD

Pathogenic

DANN

Uncertain

0.99

Eigen

Pathogenic

1.1

Eigen_PC

Pathogenic

0.94

FATHMM_MKL

Uncertain

0.93

GERP RS

5.7

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.93

SpliceAI score (max)

0.95

Details are displayed if max score is > 0.2

DS_DL_spliceai

0.95

Position offset: -1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over