2-190205149-TAA-TA

Variant names:

• chr2-190205149-TA-T
• rs863225062
• NM_014362.4:c.1128delT

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PVS1_Moderate PM2

The NM_014362.4(HIBCH):​c.1128delT​(p.Phe376LeufsTer9) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000657 in 152,184 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: HIBCH NM_014362.4 frameshift
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.13
• Publications: 1 publications found

Genes affected

HIBCH (HGNC:4908): (3-hydroxyisobutyryl-CoA hydrolase) This gene encodes the enzyme responsible for hydrolysis of both HIBYL-CoA and beta-hydroxypropionyl-CoA. Mutations in this gene have been associated with 3-hyroxyisobutyryl-CoA hydrolase deficiency. Alternative splicing results in multiple transcript variants.[provided by RefSeq, May 2010]

HIBCH Gene-Disease associations (from GenCC):

• 3-hydroxyisobutyryl-CoA hydrolase deficiency

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Orphanet, Ambry Genetics, Labcorp Genetics (formerly Invitae), G2P, ClinGen
• Leigh syndrome

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen

ACMG classification

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

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0284 CDS is truncated, and there are 1 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HIBCH	NM_014362.4	c.1128delT	p.Phe376LeufsTer9	frameshift_variant	Exon 14 of 14	ENST00000359678.10	NP_055177.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HIBCH	ENST00000359678.10	c.1128delT	p.Phe376LeufsTer9	frameshift_variant	Exon 14 of 14	1	NM_014362.4	ENSP00000352706.5

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152184 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

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: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 28

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152184 Hom.: 0 Cov.: 32 AF XY: 0.0000134 AC XY: 1 AN XY: 74350

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000241 AC: 1 AN: 41450

American (AMR) AF: 0.00 AC: 0 AN: 15278

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3468

East Asian (EAS) AF: 0.00 AC: 0 AN: 5204

South Asian (SAS) AF: 0.00 AC: 0 AN: 4834

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10620

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68010

Other (OTH) AF: 0.00 AC: 0 AN: 2092

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

3-hydroxyisobutyryl-CoA hydrolase deficiency Uncertain:1

Nov 05, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Phe376Leufs*9) in the HIBCH gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 11 amino acid(s) of the HIBCH protein. This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with HIBCH-related conditions. ClinVar contains an entry for this variant (Variation ID: 1467805). This variant disrupts a region of the HIBCH protein in which other variant(s) (p.Lys377*) have been observed in individuals with HIBCH-related conditions (PMID: 25251209). This suggests that this is a clinically significant region of the protein, and that variants that disrupt it are likely to be disease-causing. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		2.1
Mutation Taster		=10/190	disease causing

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

Other links and lift over

dbSNP: rs863225062; hg19: chr2-191069875;