X-106822125-G-T

Variant names:

• chrX-106822125-G-T
• NM_017752.3:c.509G>T

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_017752.3(TBC1D8B):​c.509G>T​(p.Gly170Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 22)
• Consequence: TBC1D8B NM_017752.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.96
• Publications: 0 publications found

Genes affected

TBC1D8B (HGNC:24715): (TBC1 domain family member 8B) This gene encodes a protein with a TBC (Tre-2/Bub2/CDC16) domain. Some mammalian proteins with this domain have been shown to function as Rab-GAPs by binding to specific Rab proteins and affecting their GTPase activity. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Sep 2011]

MORC4 (HGNC:23485): (MORC family CW-type zinc finger 4) In human, the four current members of the microrchidia (morc) gene family share an N-terminal ATPase-like ATP-binding region and a CW four-cysteine zinc-finger motif. The protein encoded by this gene also has a nuclear matrix binding domain and a two-stranded coiled-coil motif near its C-terminus. This gene is widely expressed at low levels in normal tissues and has elevated expression in placenta and testis. Alternative splicing results in multiple transcript variants encoding distinct proteins. [provided by RefSeq, Jan 2010]

ACMG classification

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.928

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TBC1D8B	NM_017752.3	c.509G>T	p.Gly170Val	missense_variant	Exon 4 of 21	ENST00000357242.10	NP_060222.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TBC1D8B	ENST00000357242.10	c.509G>T	p.Gly170Val	missense_variant	Exon 4 of 21	1	NM_017752.3	ENSP00000349781.5

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 22

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Jan 19, 2025

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.509G>T (p.G170V) alteration is located in exon 4 (coding exon 4) of the TBC1D8B gene. This alteration results from a G to T substitution at nucleotide position 509, causing the glycine (G) at amino acid position 170 to be replaced by a valine (V). 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	Pathogenic	0.75
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.56
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.81	D;.;D;D
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D;D;D
M_CAP	Pathogenic	0.56	D
MetaRNN	Pathogenic	0.93	D;D;D;D
MetaSVM	Pathogenic	0.85	D
MutationAssessor	Uncertain	2.6	M;M;.;.
PhyloP100		10
PrimateAI	Uncertain	0.79	T
PROVEAN	Pathogenic	-6.8	D;D;D;D
REVEL	Pathogenic	0.89
Sift	Pathogenic	0.0	D;D;D;D
Sift4G	Uncertain	0.0020	D;D;D;D
Polyphen		0.99	D;.;D;.
Vest4		0.94
MutPred		0.72		Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);
MVP		0.69
MPC		0.48
ClinPred		1.0	D
GERP RS		5.3
Varity_R		0.97
gMVP		0.76
Mutation Taster		=21/79	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.12		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

hg19: chrX-106065355;