chr16-81356989-G-A

Position:

• chr16-81356989-G-A

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Strong

The NM_022041.4(GAN):​c.838G>A​(p.Gly280Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000069 in 1,450,228 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: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: GAN NM_022041.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.84

Genes affected

GAN (HGNC:4137): (gigaxonin) This gene encodes a member of the cytoskeletal BTB/kelch (Broad-Complex, Tramtrack and Bric a brac) repeat family. The encoded protein plays a role in neurofilament architecture and is involved in mediating the ubiquitination and degradation of some proteins. Defects in this gene are a cause of giant axonal neuropathy (GAN). [provided by RefSeq, Oct 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a repeat Kelch 1 (size 52) in uniprot entity GAN_HUMAN there are 6 pathogenic changes around while only 0 benign (100%) in NM_022041.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.969

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAN	NM_022041.4	c.838G>A	p.Gly280Arg	missense_variant	4/11	ENST00000648994.2
GAN	NM_001377486.1	c.199G>A	p.Gly67Arg	missense_variant	3/10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAN	ENST00000648994.2	c.838G>A	p.Gly280Arg	missense_variant	4/11		NM_022041.4	P1
GAN	ENST00000648349.2	c.*546G>A		3_prime_UTR_variant, NMD_transcript_variant	3/10
GAN	ENST00000650388.1	c.*195G>A		3_prime_UTR_variant, NMD_transcript_variant	2/9

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.90e-7 AC: 1 AN: 1450228 Hom.: 0 Cov.: 29 AF XY: 0.00 AC XY: 0 AN XY: 722220

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: 9.07e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Giant axonal neuropathy 1 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 27, 2018

This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a GAN-related disease. In summary, this variant is a novel missense change with uncertain impact on mRNA splicing and protein function. It has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may alter RNA splicing, but this prediction has not been confirmed by published transcriptional studies. 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: "Probably Damaging"; Align-GVGD: "Class C0"). This sequence change replaces glycine with arginine at codon 280 of the GAN protein (p.Gly280Arg). The glycine residue is highly conserved and there is a moderate physicochemical difference between glycine and arginine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.37
CADD	Pathogenic	32
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.89	D;D
Eigen	Pathogenic	0.73
Eigen_PC	Pathogenic	0.77
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	.;D
M_CAP	Uncertain	0.19	D
MetaRNN	Pathogenic	0.97	D;D
MetaSVM	Uncertain	-0.056	T
MutationAssessor	Benign	1.1	L;L
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.77	T
Sift4G	Pathogenic	0.0	D;.
Polyphen		1.0	D;D
Vest4		0.80
MutPred		0.84		Gain of MoRF binding (P = 0.0167);Gain of MoRF binding (P = 0.0167);
MVP		0.94
MPC		0.59
ClinPred		0.99	D
GERP RS		5.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.60
gMVP		0.89

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1270020554; hg19: chr16-81390594;