rs1251443902

Variant names:

• chr9-6645371-GT-G
• rs1251443902
• NM_000170.3:c.128delA

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000170.3(GLDC):​c.128delA​(p.Asp43AlafsTer48) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000132 in 151,988 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: 𝑓 0.000013 (0 hom., cov: 32)
• Consequence: GLDC NM_000170.3 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 0.116

Genes affected

GLDC (HGNC:4313): (glycine decarboxylase) Degradation of glycine is brought about by the glycine cleavage system, which is composed of four mitochondrial protein components: P protein (a pyridoxal phosphate-dependent glycine decarboxylase), H protein (a lipoic acid-containing protein), T protein (a tetrahydrofolate-requiring enzyme), and L protein (a lipoamide dehydrogenase). The protein encoded by this gene is the P protein, which binds to glycine and enables the methylamine group from glycine to be transferred to the T protein. Defects in this gene are a cause of nonketotic hyperglycinemia (NKH).[provided by RefSeq, Jan 2010]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 9-6645371-GT-G is Pathogenic according to our data. Variant chr9-6645371-GT-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 552137.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr9-6645371-GT-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
GLDC	NM_000170.3	c.128delA	p.Asp43AlafsTer48	frameshift_variant	Exon 1 of 25	ENST00000321612.8	NP_000161.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
GLDC	ENST00000321612.8	c.128delA	p.Asp43AlafsTer48	frameshift_variant	Exon 1 of 25	1	NM_000170.3	ENSP00000370737.4

Frequencies

GnomAD3 genomes AF: 0.0000132 AC: 2 AN: 151988 Hom.: 0 Cov.: 32

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: 0.0000294

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 32

GnomAD4 genome AF: 0.0000132 AC: 2 AN: 151988 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74248

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: 0.0000294

Gnomad4 OTH AF: 0.00

Bravo AF: 0.0000113

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Glycine encephalopathy Pathogenic:5

May 23, 2017

Counsyl

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Mar 08, 2021

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: GLDC c.128delA (p.Asp43AlafsX48) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory. The variant allele was found at a frequency of 1.3e-05 in 150762 control chromosomes (gnomAD v3.1). c.128delA has been reported in the literature in individuals affected with Glycine Encephalopathy (Non-Ketotic Hyperglycinemia) (e.g. Swanson_2015, Coughlin_2017) and is included as a pathogenic variant in targeted testing panels for Amish communities (e.g. Crowgey_2019, Clinic for Special Children). Three ClinVar submitters (evaluation after 2014) cite the variant as pathogenic/likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Feb 07, 2018

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.Asp43AlafsX48 (NM_000170.2 c.128delA) variant in GLDC has been previously reported in 1 compound heterozygous individual with glycine encephalopathy (Swan son 2015), and was absent from large population studies. This variant is predict ed to cause a frameshift, which alters the protein?s amino acid sequence beginni ng at position 43 and leads to a premature termination codon 48 amino acids down stream. This alteration is then predicted to lead to a truncated or absent prote in. Biallelic loss of function of the GLDC gene is associated with glycine encep halopathy. In summary, the p.Asp43AlafsX48 variant meets our criteria to be clas sified as pathogenic for glycine encephalopathy in an autosomal recessive manner based on its occurrence in trans with another pathogenic variant in an affected individual and its predicted impact on the protein. -

Apr 05, 2021

Natera, Inc.

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Jul 27, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. ClinVar contains an entry for this variant (Variation ID: 552137). This premature translational stop signal has been observed in individual(s) with encephalopathy (PMID: 30609409). This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Asp43Alafs*48) in the GLDC gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in GLDC are known to be pathogenic (PMID: 16601880). -

not provided Pathogenic:1

Mar 26, 2023

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Has been reported (as c.127_128delAfs*47, due to use of alternate nomenclature) in trans with a splice site variant in a patient with severe nonketotic hyperglycinemia (Swanson et al., 2015); Frameshift variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss-of-function is a known mechanism of disease; Not observed in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 26179960, 30609409) -

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: rs1251443902; hg19: chr9-6645371;