chr9-6553502-G-A

Position:

• chr9-6553502-G-A

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PM5 PP3_Moderate PP5_Moderate

The NM_000170.3(GLDC):​c.2323C>T​(p.His775Tyr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,640 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 Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. H775P) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: GLDC NM_000170.3 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 9.60

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]

GLDC (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 10 ACMG points.

• PM1: In a helix (size 5) in uniprot entity GCSP_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_000170.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr9-6553501-T-G is described in Lovd as [Pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.893
• PP5: Variant 9-6553502-G-A is Pathogenic according to our data. Variant chr9-6553502-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 531764.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GLDC	NM_000170.3	c.2323C>T	p.His775Tyr	missense_variant	20/25	ENST00000321612.8	NP_000161.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GLDC	ENST00000321612.8	c.2323C>T	p.His775Tyr	missense_variant	20/25	1	NM_000170.3	ENSP00000370737.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461640 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 727140

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: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000312 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Glycine encephalopathy Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 18, 2018

This sequence change replaces histidine with tyrosine at codon 775 of the GLDC protein (p.His775Tyr). The histidine residue is highly conserved and there is a moderate physicochemical difference between histidine and tyrosine. This variant is not present in population databases (ExAC no frequency). This variant has been observed in an individual with biochemical findings that are highly specific for glycine encephalopathy (Invitae). 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: "Possibly Damaging"; Align-GVGD: "Class C0"). Two additional missense substitution at this codon (p.His775Arg, p.His775Pro) have been reported in trans with pathogenic variants in the GLDC gene in individuals affected with glycine encephalopathy (PMID: 16601880, 27362913). This suggests that the histidine residue is critical for GLDC protein function. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.33
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.36
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.79	D;.;.;.
Eigen	Pathogenic	0.93
Eigen_PC	Pathogenic	0.78
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	0.99	D;D;D;D
M_CAP	Pathogenic	0.67	D
MetaRNN	Pathogenic	0.89	D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.4	H;.;.;.
PrimateAI	Uncertain	0.75	T
PROVEAN	Pathogenic	-5.7	D;.;.;.
REVEL	Pathogenic	0.89
Sift	Pathogenic	0.0	D;.;.;.
Sift4G	Pathogenic	0.0	D;.;.;.
Polyphen		1.0	D;.;.;.
Vest4		0.85
MutPred		0.55		Loss of disorder (P = 0.0433);.;.;.;
MVP		0.99
MPC		0.24
ClinPred		1.0	D
GERP RS		4.7
Varity_R		0.90
gMVP		0.90

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.11		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: rs1554643619; hg19: chr9-6553502;