X-101346662-T-C

Position:

• chrX-101346662-T-C

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PVS1 PM2 PP3_Strong

The NM_004085.4(TIMM8A):​c.133-2A>G variant causes a splice acceptor change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 2/2 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 23)
• Consequence: TIMM8A NM_004085.4 splice_acceptor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.75

Genes affected

TIMM8A (HGNC:11817): (translocase of inner mitochondrial membrane 8A) This translocase is involved in the import and insertion of hydrophobic membrane proteins from the cytoplasm into the mitochondrial inner membrane. The gene is mutated in Mohr-Tranebjaerg syndrome/Deafness Dystonia Syndrome (MTS/DDS) and it is postulated that MTS/DDS is a mitochondrial disease caused by a defective mitochondrial protein import system. Defects in this gene also cause Jensen syndrome; an X-linked disease with opticoacoustic nerve atrophy and muscle weakness. This protein, along with TIMM13, forms a 70 kDa heterohexamer. Alternative splicing results in multiple transcript variants encoding distinct isoforms.[provided by RefSeq, Mar 2009]

ACMG classification

Verdict is Pathogenic. Variant got 14 ACMG points.

• PVS1: Splicing variant, LoF is a know mechanism of disease,
• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TIMM8A	NM_004085.4	c.133-2A>G		splice_acceptor_variant		ENST00000372902.4
TIMM8A	NM_001145951.2	c.*1725A>G		3_prime_UTR_variant	2/2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TIMM8A	ENST00000372902.4	c.133-2A>G		splice_acceptor_variant		1	NM_004085.4	P1
TIMM8A	ENST00000644112.2	c.*1725A>G		3_prime_UTR_variant	2/2
TIMM8A	ENST00000645279.1	c.*327-2A>G		splice_acceptor_variant, NMD_transcript_variant
TIMM8A	ENST00000647480.1	n.650-2A>G		splice_acceptor_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 23

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

Aug 23, 2019

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. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. This variant has not been reported in the literature in individuals with TIMM8A-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change affects an acceptor splice site in the last intron (intron 1) of the TIMM8A gene. While this is not anticipated to result in nonsense mediated decay, it likely alters RNA splicing and results in a disrupted protein product. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.74	D
BayesDel_noAF	Pathogenic	0.16
CADD	Pathogenic	29
DANN	Uncertain	0.99
FATHMM_MKL	Uncertain	0.87	D
MutationTaster	Benign	1.0	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
SpliceAI score (max)		0.98		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.67		Position offset: 32
DS_AL_spliceai		0.98		Position offset: -2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1926076610; hg19: chrX-100601650;