rs1555423104

Variant names:

• chr15-90790742-T-A
• rs1555423104
• NM_000057.4:c.2917T>A

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM2 PP3_Strong

The NM_000057.4(BLM):​c.2917T>A​(p.Tyr973Asn) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,824 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Synonymous variant affecting the same amino acid position (i.e. Y973Y) has been classified as Benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.92
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• Bloom syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Myriad Women’s Health, Labcorp Genetics (formerly Invitae), G2P, Laboratory for Molecular Medicine, Orphanet, Genomics England PanelApp, ClinGen
• osteosarcoma

  Inheritance: AR Classification: MODERATE Submitted by: Genomics England PanelApp
• breast cancer

  Inheritance: AD Classification: NO_KNOWN Submitted by: Ambry Genetics
• hereditary nonpolyposis colon cancer

  Inheritance: AD Classification: NO_KNOWN Submitted by: Ambry Genetics

ENSG00000300894 (HGNC:):

ACMG classification

Our verdict: Likely_pathogenic. The variant received 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.975

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BLM	NM_000057.4	c.2917T>A	p.Tyr973Asn	missense_variant	Exon 15 of 22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.2917T>A	p.Tyr973Asn	missense_variant	Exon 15 of 22	1	NM_000057.4	ENSP00000347232.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461824 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727212

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26132

East Asian (EAS) AF: 0.00 AC: 0 AN: 39692

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111964

Other (OTH) AF: 0.00 AC: 0 AN: 60390

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Bloom syndrome Uncertain:1

Aug 03, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). 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. This variant has not been reported in the literature in individuals with BLM-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces tyrosine with asparagine at codon 973 of the BLM protein (p.Tyr973Asn). The tyrosine residue is highly conserved and there is a large physicochemical difference between tyrosine and asparagine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.43	D
BayesDel_noAF	Pathogenic	0.39
CADD	Pathogenic	33
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.77	D;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.95
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	1.0	D;D
M_CAP	Pathogenic	0.69	D
MetaRNN	Pathogenic	0.98	D;D
MetaSVM	Pathogenic	0.87	D
MutationAssessor	Pathogenic	4.7	H;.
PhyloP100		7.9
PrimateAI	Uncertain	0.79	T
PROVEAN	Pathogenic	-8.7	D;D
REVEL	Pathogenic	0.87
Sift	Pathogenic	0.0	D;D
Sift4G	Pathogenic	0.0	D;D
Polyphen		1.0	D;.
Vest4		0.99
MutPred		0.83		Loss of phosphorylation at Y973 (P = 0.0348);Loss of phosphorylation at Y973 (P = 0.0348);
MVP		0.95
MPC		0.61
ClinPred		1.0	D
GERP RS		5.4
Varity_R		0.99
gMVP		0.93
Mutation Taster		=8/92	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.35		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.35		Position offset: -3

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

Other links and lift over

dbSNP: rs1555423104; hg19: chr15-91333972;