16-5082676-A-G

Position:

• chr16-5082676-A-G

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PM2 PP3_Moderate PP5_Very_Strong

The NM_019109.5(ALG1):​c.1187+3A>G variant causes a splice donor region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000218 in 1,611,132 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 Likely pathogenic (★★).

• Frequency:
  • Genomes: 𝑓 0.00012 (0 hom., cov: 33)
  • Exomes 𝑓: 0.00023 (0 hom.)
• Consequence: ALG1 NM_019109.5 splice_donor_region, intron
• Scores: Splicing: ADA: 0.9997
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:14 O:1
• Conservation: PhyloP100: 3.37

Genes affected

ALG1 (HGNC:18294): (ALG1 chitobiosyldiphosphodolichol beta-mannosyltransferase) The enzyme encoded by this gene catalyzes the first mannosylation step in the biosynthesis of lipid-linked oligosaccharides. This gene is mutated in congenital disorder of glycosylation type Ik. [provided by RefSeq, Dec 2008]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 16-5082676-A-G is Pathogenic according to our data. Variant chr16-5082676-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 224118.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr16-5082676-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
ALG1	NM_019109.5	c.1187+3A>G		splice_donor_region_variant, intron_variant		ENST00000262374.10
ALG1	NM_001330504.2	c.854+3A>G		splice_donor_region_variant, intron_variant
ALG1	XM_017023457.3	c.1148+3A>G		splice_donor_region_variant, intron_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
ALG1	ENST00000262374.10	c.1187+3A>G		splice_donor_region_variant, intron_variant		1	NM_019109.5	P1

Frequencies

GnomAD3 genomes AF: 0.000118 AC: 18 AN: 152218 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000482

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: 0.000235

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000100 AC: 25 AN: 249520 Hom.: 0 AF XY: 0.000111 AC XY: 15 AN XY: 135146

Gnomad AFR exome AF: 0.000124

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: 0.000204

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.000229 AC: 334 AN: 1458914 Hom.: 0 Cov.: 34 AF XY: 0.000227 AC XY: 165 AN XY: 725798

Gnomad4 AFR exome AF: 0.0000299

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: 0.000291

Gnomad4 OTH exome AF: 0.000166

GnomAD4 genome AF: 0.000118 AC: 18 AN: 152218 Hom.: 0 Cov.: 33 AF XY: 0.0000941 AC XY: 7 AN XY: 74366

Gnomad4 AFR AF: 0.0000482

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: 0.000235

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000107 Hom.: 0

Bravo AF: 0.000117

EpiCase AF: 0.000109

EpiControl AF: 0.000296

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:14 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

ALG1-congenital disorder of glycosylation Pathogenic:8 Other:1

Pathogenic, criteria provided, single submitter	clinical testing	Knight Diagnostic Laboratories, Oregon Health and Sciences University	Feb 22, 2019	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Undiagnosed Diseases Network, NIH	Jun 23, 2017	Clinical genome sequencing revealed 3 variants of uncertain significance in the ALG1 gene. Multiple lines of computational evidence support a deleterious effect of these variants on the gene or gene product. cDNA experiments performed on a research basis demonstrated that the paternally inherited variant (c.1187+3A>G) is damaging. The maternally inherited variants are rare and are not present in the 1000 Genomes Project nor the Exome Aggregate Consortium (ExAC) databases. Based on these findings, the clinical team elevated these variants to likely pathogenic. -
Likely pathogenic, criteria provided, single submitter	research	HudsonAlpha Institute for Biotechnology, HudsonAlpha Institute for Biotechnology	Feb 09, 2017	- -
Pathogenic, criteria provided, single submitter	research	Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard	Dec 03, 2018	The homozygous c.1187+3A>G variant in ALG1 was identified by our study in one individual with congenital disorder of glycosylation. The c.1187+3A>G variant in ALG1 has been reported in 1 individual with congenital disorder of glycosylation (PMID: 26931382), and has been identified in 0.01906% (24/125942) of European (non-Finnish) chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs369160589). Although this variant has been seen in the general population, its frequency is low enough to be consistent with a recessive carrier frequency and the presence of this variant in combination with a reported pathogenic variant and in an individual with congenital disorder of glycosylation increases the likelihood that the c.1187+3A>G variant is pathogenic (PMID: 26931382; Variation ID: 4724). This variant is located in the 5' splice region. Computational tools do suggest an impact to splicing and cDNA analysis by the NIH Undiagnosed Diseases Network demonstrated this variant has a damaging effect (Variation ID: 224118). A biomarker for loss of function in ALG1, xeno-tetrasaccharide, was detected in the serum of an individual with this variant in the compound heterozygous state (PMID: 26931382). Loss of function of the ALG1 gene is an established disease mechanism in autosomal recessive congenital disorder of glycosylation and there is evidence that this gene is necessary for survival (PMID: 26931382). However, these types of assays may not accurately represent biological function and this information is not predictive enough to determine pathogenicity. This variant has also been reported as likely pathogenic in ClinVar by multiple submitters (Variation ID: 224118). Two additional variants in this splice region have been reported pathogenic in ClinVar, raising the possibility that this splice region is a mutational hot spot (Variation ID: 95934, 194107). In summary, this variant meets criteria to be classified as pathogenic for congenital disorder of glycosylation in an autosomal recessive manner based on the predicted impact of the variant and our findings in the literature and ClinVar. ACMG/AMP Criteria applied: PM2, PM3, PS3, PVS1, PM1_Supporting (Richards 2015). -
Likely pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Mar 25, 2022	Variant summary: ALG1 c.1187+3A>G alters a conserved nucleotide located close to a canonical splice site and therefore could affect mRNA splicing, leading to a significantly altered protein sequence. Several computational tools predict a significant impact on normal splicing: Three predict the variant abolishes a canonical 5 splicing donor site. One predicts the variant weakens a canonical 5' donor site. At least one publication reports experimental evidence that this variant affects mRNA splicing and results in intron 11 retention, causing a stop-gain after adding 84 nucleotides (28 codons) (Bowling_2017). The variant allele was found at a frequency of 0.0001 in 249520 control chromosomes. This frequency is not significantly higher than expected for a pathogenic variant in ALG1 causing Congenital Disorder Of Glycosylation Type 1K (0.0001 vs 0.0011), allowing no conclusion about variant significance. c.1187+3A>G has been reported in the literature in individuals affected with Congenital Disorder Of Glycosylation (Ng_2016, Bowling_2017, Burdick_2020). These data indicate that the variant may be associated with disease. Nine ClinVar submitters (evaluation after 2014) cite the variant as pathogenic (n=4) and likely pathogenic (n=5). Based on the evidence outlined above, the variant was classified as likely pathogenic. -
not provided, no classification provided	phenotyping only	GenomeConnect - Brain Gene Registry	-	Variant classified as Pathogenic and reported on 07-27-2021 by Invitae. Assertions are reported exactly as they appear on the patient provided laboratory report. GenomeConnect does not attempt to reinterpret the variant. The IDDRC-CTSA National Brain Gene Registry (BGR) is a study funded by the U.S. National Center for Advancing Translational Sciences (NCATS) and includes 13 Intellectual and Developmental Disability Research Center (IDDRC) institutions. The study is led by Principal Investigator Dr. Philip Payne from Washington University. The BGR is a data commons of gene variants paired with subject clinical information. This database helps scientists learn more about genetic changes and their impact on the brain and behavior. Participation in the Brain Gene Registry requires participation in GenomeConnect. More information about the Brain Gene Registry can be found on the study website - https://braingeneregistry.wustl.edu/. -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 26, 2023	This sequence change falls in intron 11 of the ALG1 gene. It does not directly change the encoded amino acid sequence of the ALG1 protein. RNA analysis indicates that this variant induces altered splicing and may result in an absent or disrupted protein product. This variant is present in population databases (rs369160589, gnomAD 0.02%). This variant has been observed in individual(s) with congenital disorders of glycosylation (PMID: 26931382, 32190976). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 224118). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Studies have shown that this variant results in retention of intron 11 of the ALG1 gene and introduces a premature termination codon (PMID: 28554332). The resulting mRNA is expected to undergo nonsense-mediated decay. For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Victorian Clinical Genetics Services, Murdoch Childrens Research Institute	Sep 02, 2022	Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Pathogenic. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with congenital disorder of glycosylation, type Ik (MIM#608540). (I) 0106 - This gene is associated with autosomal recessive disease. (I) 0210 - Splice site variant proven to affect splicing of the transcript with a known effect on protein sequence. Quantitative PCR from a patient's blood RNA showed the variant led to increased retention of intron 11, which is predicted to result in a premature stop codon and nonsense-mediated decay (NMD) of RNA (PMID: 28554332). (SP) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD (v2) <0.01 for a recessive condition (25 heterozygotes, 0 homozygotes). (SP) 0600 - Variant is located in the annotated glycosyl transferases group 1 domain (DECIPHER). (I) 0702 - Other premature termination variants comparable to the one identified in this case have strong previous evidence for pathogenicity. Many NMD-predicted variants have been reported as likely pathogenic/pathogenic in ClinVar. (SP) 0801 - This variant has strong previous evidence of pathogenicity in unrelated individuals. It has been reported as likely pathogenic/pathogenic multiple times in ClinVar, and as compound heterozygous with p.(Ser258Leu) in an affected individual with type I congenital disorder of glycosylation (PMIDs: 26931382, 28554332). (SP) 1206 - This variant has been shown to be paternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -
Likely pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Feb 11, 2022	- -

Congenital disorder of glycosylation Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	May 27, 2020	VARIANT INTERPRETATION: The c.1187+3A>G variant in ALG1 has been reported in three individuals with congenital disorders of glycosylation. One is homozygous and two are compound heterozygous with the p.Ser258Leu variant in ALG1 (Ng 2016 26931382, Bowling 2017 28554332, SCV001164452.1). It has also been identified in 0.02% (23/112692) of European chromosomes by gnomAD (http://gnomad.broadinstitute.org) and is reported in ClinVar (Variation ID: 224118). This variant is located in the 5' splice region. In vitro qPCR analysis demonstrates a retention of exon 11 and a stop gain after the addition of 84 nucleotides, consistent with pathogenicity (Bowling 2017 28554332). In summary, this variant meets criteria to be classified as pathogenic for autosomal recessive Congenital disorders of glycosylation. ACMG/AMP Criteria applied: PS3, PM3_Strong. -
Likely pathogenic, no assertion criteria provided	research	University of Washington Center for Mendelian Genomics, University of Washington	May 25, 2017	- -

ALG1-related disorder Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Sep 03, 2022

The ALG1 c.1187+3A>G variant is predicted to interfere with splicing. This variant has been reported in the compound heterozygous state in individuals with congenital disorder of glycosylation (Ng et al. 2016. PubMed ID: 26931382; Bowling et al. 2017. PubMed ID: 28554332; Burdick et al. 2020. PubMed ID: 32190976). RT-PCR analysis indicated this variant leads to retention of intron 11, resulting in addition of 84 nucleotides (28 codons) and a stop gain (Bowling et al. 2017. PubMed ID: 28554332; González-Domínguez et al. 2021. PubMed ID: 34567092). An additional genome study also confirmed that this variant disrupted splicing (Burdick et al. 2020. PubMed ID: 32190976). This variant is reported in 0.020% of alleles in individuals of European (Non-Finnish) descent in gnomAD (http://gnomad.broadinstitute.org/variant/16-5132677-A-G). This variant is interpreted as likely pathogenic. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Oct 25, 2022

Non-canonical splice site variant demonstrated to result in loss of function (Bowling et al., 2017); This variant is associated with the following publications: (PMID: 26931382, 28554332, 32190976) -

Congenital disorder of glycosylation type I Pathogenic:1

Likely pathogenic, criteria provided, single submitter

curation

Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard

May 02, 2023

The heterozygous c.1187+3A>G variant in ALG1 was identified by our study, in the compound heterozygous state with a variant of uncertain significance (ClinVar Variation ID: 1483545), in one individual with intrauterine growth restriction,microcephaly, brain abnormalities, and hypertonia. Trio exome analysis revealed that this variant was in trans with a variant of uncertain significance (ClinVar Variation ID: 1483545). The c.1187+3A>G variant in ALG1 has been reported in two individuals with congenital disorder of glycosylation type I (PMID: 26931382, SCV001164452.1), but has been identified in 0.02% (16/68040) of European (non-Finnish) chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP ID: rs369160589). Although this variant has been seen in the general population in a heterozygous state, its frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar (Variation ID: 224118) and has been interpreted as pathogenic or likely pathogenic by multiple submitters. Of the two affected individuals previously reported, one was a homozygote (SCV001164452.1) and one was a compound heterozygote who carried a reported likely pathogenic variant in trans (PMID: 26931382, PMID: 28554332, ClinVar Variation ID: 4724), which increases the likelihood that the c.1187+3A>G variant is pathogenic. RT-PCR analysis performed on affected tissue showed evidence of intron retention before exon 12, leading to a premature stop codon after addition of 84bp (PMID: 28554332). This variant is located in the 5’ splice region. Computational tools do suggest an impact to splicing. However, this information is not predictive enough to determine pathogenicity. In summary, although additional studies are required to fully establish its clinical significance, this variant is likely pathogenic for autosomal recessive congenital disorder of glycosylation type I. ACMG/AMP Criteria applied: PS3_Moderate, PM3, PM2_Supporting, PP4 (Richards 2015). -

Encephalopathy Pathogenic:1

Pathogenic, criteria provided, single submitter

research

Equipe Genetique des Anomalies du Developpement, Université de Bourgogne

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.32
CADD	Benign	23
DANN	Benign	0.96

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.96
SpliceAI score (max)		0.66		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.66		Position offset: -3

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

Publications

LitVar

Other links and lift over

dbSNP: rs369160589; hg19: chr16-5132677;