chr9-137087074-C-CG

Position:

• chr9-137087074-C-CG

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PVS1 PM2 PP5

The NM_016219.5(MAN1B1):​c.79dup​(p.Ala27GlyfsTer35) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000207 in 1,450,440 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: MAN1B1 NM_016219.5 frameshift
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 0.413

Genes affected

MAN1B1 (HGNC:6823): (mannosidase alpha class 1B member 1) This gene encodes an enzyme belonging to the glycosyl hydrolase 47 family. This enzyme functions in N-glycan biosynthesis, and is a class I alpha-1,2-mannosidase that specifically converts Man9GlcNAc to Man8GlcNAc isomer B. It is required for N-glycan trimming to Man5-6GlcNAc2 in the endoplasmic-reticulum-associated degradation pathway. Mutations in this gene cause autosomal-recessive intellectual disability. Alternative splicing results in multiple transcript variants. A related pseudogene has been identified on chromosome 11. [provided by RefSeq, Dec 2011]

ACMG classification

Verdict is Pathogenic. Variant got 11 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 30 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 9-137087074-C-CG is Pathogenic according to our data. Variant chr9-137087074-C-CG is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 632038.We mark this variant Likely_pathogenic, oryginal submissions are: {Pathogenic=1, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MAN1B1	NM_016219.5	c.79dup	p.Ala27GlyfsTer35	frameshift_variant	1/13	ENST00000371589.9
MAN1B1	XM_006716945.5	c.79dup	p.Ala27GlyfsTer35	frameshift_variant	1/12
MAN1B1	NR_045720.2	n.94dup		non_coding_transcript_exon_variant	1/13
MAN1B1	NR_045721.2	n.94dup		non_coding_transcript_exon_variant	1/14

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MAN1B1	ENST00000371589.9	c.79dup	p.Ala27GlyfsTer35	frameshift_variant	1/13	1	NM_016219.5	P2

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 0.00000207 AC: 3 AN: 1450440 Hom.: 0 Cov.: 31 AF XY: 0.00000278 AC XY: 2 AN XY: 720578

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: 0.0000167

GnomAD4 genome Cov.: 34

Alfa AF: 0.0000843 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Inborn genetic diseases Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Feb 13, 2018

The c.79dupG pathogenic mutation, located in coding exon 1 of the MAN1B1 gene, results from a duplication of G at nucleotide position 79, causing a translational frameshift with a predicted alternate stop codon (p.A27Gfs*35). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Rafiq syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Apr 28, 2017

The MAN1B1 c.79dupG (p.Ala27GlyfsTer35) variant results in a frameshift and is predicted to result in premature termination of the protein. It was observed by ICSL as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018) and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score for this variant, it could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene and cDNA change, and amino acid change. No publications were found based on this search. Due to the potential impact of frameshift variants and the lack of clarifying evidence, this variant is classified as a variant of unknown significance but suspicious for pathogenicity for autosomal recessive intellectual disability. -

Computational scores

Source: dbNSFP v4.3

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: rs1190243291; hg19: chr9-139981526;