5-74721774-T-G

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_032380.5(GFM2):c.2221A>C(p.Thr741Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000124 in 1,611,422 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 (★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: GFM2 NM_032380.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.67

Genes affected

GFM2 (HGNC:29682): (GTP dependent ribosome recycling factor mitochondrial 2) Eukaryotes contain two protein translational systems, one in the cytoplasm and one in the mitochondria. Mitochondrial translation is crucial for maintaining mitochondrial function and mutations in this system lead to a breakdown in the respiratory chain-oxidative phosphorylation system and to impaired maintenance of mitochondrial DNA. This gene encodes one of the mitochondrial translation elongation factors, which is a GTPase that plays a role at the termination of mitochondrial translation by mediating the disassembly of ribosomes from messenger RNA . Its role in the regulation of normal mitochondrial function and in disease states attributed to mitochondrial dysfunction is not known. Alternative splicing results in multiple transcript variants encoding distinct isoforms. [provided by RefSeq, Jul 2013]

HEXB (HGNC:4879): (hexosaminidase subunit beta) Hexosaminidase B is the beta subunit of the lysosomal enzyme beta-hexosaminidase that, together with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules containing terminal N-acetyl hexosamines. Beta-hexosaminidase is composed of two subunits, alpha and beta, which are encoded by separate genes. Both beta-hexosaminidase alpha and beta subunits are members of family 20 of glycosyl hydrolases. Mutations in the alpha or beta subunit genes lead to an accumulation of GM2 ganglioside in neurons and neurodegenerative disorders termed the GM2 gangliosidoses. Beta subunit gene mutations lead to Sandhoff disease (GM2-gangliosidosis type II). Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, May 2014]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.932

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GFM2	NM_032380.5	c.2221A>C	p.Thr741Pro	missense_variant	21/21	ENST00000296805.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GFM2	ENST00000296805.8	c.2221A>C	p.Thr741Pro	missense_variant	21/21	1	NM_032380.5	P1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152198 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: 0.0000941

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1459224 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 725842

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: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152198 Hom.: 0 Cov.: 32 AF XY: 0.0000134 AC XY: 1 AN XY: 74366

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: 0.0000941

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Feb 18, 2022

This variant has not been reported in the literature in individuals affected with GFM2-related conditions. 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. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant is present in population databases (no rsID available, gnomAD 0.03%). This sequence change replaces threonine, which is neutral and polar, with proline, which is neutral and non-polar, at codon 741 of the GFM2 protein (p.Thr741Pro). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.39
BayesDel_addAF	Pathogenic	0.37	D
BayesDel_noAF	Pathogenic	0.30
Cadd	Pathogenic	27
Dann	Uncertain	1.0
DEOGEN2	Benign	0.035	T;.;T
Eigen	Pathogenic	0.79
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Pathogenic	1.0	D
M_CAP	Uncertain	0.17	D
MetaRNN	Pathogenic	0.93	D;D;D
MetaSVM	Uncertain	-0.038	T
MutationAssessor	Pathogenic	3.2	M;.;M
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.52	T
PROVEAN	Uncertain	-4.4	D;D;D
REVEL	Pathogenic	0.78
Sift	Uncertain	0.0040	D;D;D
Sift4G	Uncertain	0.0040	D;D;D
Polyphen		1.0	D;D;D
Vest4		0.70
MutPred		0.80		Loss of catalytic residue at T741 (P = 0.0151);.;Loss of catalytic residue at T741 (P = 0.0151);
MVP		0.91
MPC		0.77
ClinPred		1.0	D
GERP RS		5.8
Varity_R		0.95
gMVP		0.87

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs773006254; hg19: chr5-74017599;