2-101008047-G-C

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_001330348.2(TBC1D8):c.3242C>G(p.Thr1081Arg) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000607 in 1,613,838 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000033 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000064 (1 hom.)
• Consequence: TBC1D8 NM_001330348.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.262

Genes affected

TBC1D8 (HGNC:17791): (TBC1 domain family member 8) Predicted to enable GTPase activator activity. Predicted to be involved in activation of GTPase activity and intracellular protein transport. Predicted to be located in membrane. [provided by Alliance of Genome Resources, Apr 2022]

RPL31 (HGNC:10334): (ribosomal protein L31) Ribosomes, the organelles that catalyze protein synthesis, consist of a small 40S subunit and a large 60S subunit. Together these subunits are composed of 4 RNA species and approximately 80 structurally distinct proteins. This gene encodes a ribosomal protein that is a component of the 60S subunit. The protein belongs to the L31E family of ribosomal proteins. It is located in the cytoplasm. Higher levels of expression of this gene in familial adenomatous polyps compared to matched normal tissues have been observed. As is typical for genes encoding ribosomal proteins, there are multiple processed pseudogenes of this gene dispersed through the genome. Alternatively spliced transcript variants encoding distinct isoforms have been found for this gene. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.011097521).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TBC1D8	NM_001330348.2	c.3242C>G	p.Thr1081Arg	missense_variant	20/20	ENST00000409318.2
TBC1D8	NM_001102426.3	c.3197C>G	p.Thr1066Arg	missense_variant	20/20
RPL31	NM_001098577.3	c.346+1976G>C		intron_variant
TBC1D8	NR_138475.2	n.3208C>G		non_coding_transcript_exon_variant	19/19

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TBC1D8	ENST00000409318.2	c.3242C>G	p.Thr1081Arg	missense_variant	20/20	5	NM_001330348.2	A1

Frequencies

GnomAD3 genomes AF: 0.0000329 AC: 5 AN: 152140 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: 0.00104

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000132 AC: 33 AN: 249148 Hom.: 0 AF XY: 0.000200 AC XY: 27 AN XY: 135188

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00108

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000636 AC: 93 AN: 1461698 Hom.: 1 Cov.: 34 AF XY: 0.0000976 AC XY: 71 AN XY: 727130

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: 0.00105

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome AF: 0.0000329 AC: 5 AN: 152140 Hom.: 0 Cov.: 32 AF XY: 0.0000538 AC XY: 4 AN XY: 74334

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00104

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ExAC AF: 0.000157 AC: 19

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 06, 2021

The c.3197C>G (p.T1066R) alteration is located in exon 20 (coding exon 20) of the TBC1D8 gene. This alteration results from a C to G substitution at nucleotide position 3197, causing the threonine (T) at amino acid position 1066 to be replaced by an arginine (R). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.078
BayesDel_addAF	Benign	-0.60	T
BayesDel_noAF	Benign	-0.69
Cadd	Benign	0.86
Dann	Benign	0.63
DEOGEN2	Benign	0.016	T;.
Eigen	Benign	-1.2
Eigen_PC	Benign	-1.3
FATHMM_MKL	Benign	0.086	N
LIST_S2	Benign	0.54	T;T
M_CAP	Benign	0.0047	T
MetaRNN	Benign	0.011	T;T
MetaSVM	Benign	-0.93	T
MutationAssessor	Benign	0.81	L;.
MutationTaster	Benign	1.0	N;N;N;N;N
PrimateAI	Benign	0.32	T
PROVEAN	Benign	-1.2	N;N
REVEL	Benign	0.021
Sift	Benign	0.60	T;T
Sift4G	Benign	0.30	T;T
Polyphen		0.033	B;.
Vest4		0.13
MutPred		0.28		Loss of phosphorylation at T1066 (P = 0.0047);.;
MVP		0.061
MPC		0.31
ClinPred		0.015	T
GERP RS		-5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.2
Varity_R		0.051
gMVP		0.20

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: rs201882166; hg19: chr2-101624509;