rs568718845

Variant names:

• chr1-23814186-T-C
• rs568718845
• NM_000191.3:c.497+4A>G

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3 PP5

The NM_000191.3(HMGCL):​c.497+4A>G variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000616 in 1,461,262 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.0000062 (0 hom.)
• Consequence: HMGCL NM_000191.3 splice_region, intron
• Scores: Splicing: ADA: 0.9836
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 1.99

Genes affected

HMGCL (HGNC:5005): (3-hydroxy-3-methylglutaryl-CoA lyase) The protein encoded by this gene belongs to the HMG-CoA lyase family. It is a mitochondrial enzyme that catalyzes the final step of leucine degradation and plays a key role in ketone body formation. Mutations in this gene are associated with HMG-CoA lyase deficiency. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Oct 2009]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• 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. Scorers claiming Benign: dbscSNV1_RF.
• PP5: Variant 1-23814186-T-C is Pathogenic according to our data. Variant chr1-23814186-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 431913.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=1}. Variant chr1-23814186-T-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HMGCL	NM_000191.3	c.497+4A>G		splice_region_variant, intron_variant	Intron 5 of 8	ENST00000374490.8	NP_000182.2
HMGCL	NM_001166059.2	c.348+2489A>G		intron_variant	Intron 4 of 6		NP_001159531.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HMGCL	ENST00000374490.8	c.497+4A>G		splice_region_variant, intron_variant	Intron 5 of 8	1	NM_000191.3	ENSP00000363614.3

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.0000119 AC: 3 AN: 251470 Hom.: 0 AF XY: 0.0000221 AC XY: 3 AN XY: 135908

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000264

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000616 AC: 9 AN: 1461262 Hom.: 0 Cov.: 31 AF XY: 0.00000825 AC XY: 6 AN XY: 726968

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: 0.00000809

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

Alfa AF: 0.0000282 Hom.: 0

Bravo AF: 0.0000113

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Deficiency of hydroxymethylglutaryl-CoA lyase Pathogenic:1 Uncertain:1

Jan 20, 2024

Baylor Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Feb 14, 2017

Counsyl

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not provided Pathogenic:1

Oct 05, 2015

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

An individual with symptoms associated with HMG-CoA lyase deficiency was heterozygous for this variant and a nonsense variant; however, parental testing was not done to confirm the variants were in trans (Menao et al., 2009). Functional analysis found that the c.497+4 A>G variant results in alternative splicing with 2 transcripts, one bearing a five-exon deletion and the other with deletion of exons 5 and 6 (Menao et al., 2009). Additionally, this nucleotide substitution occurs at a position that is conserved across species and several in-silico splice prediction models predict that c.497+4 A>G creates a cryptic donor site in intron 5. Therefore, this variant is likely pathogenic; however, the possibility that it is benign cannot be excluded. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.36
CADD	Benign	14
DANN	Benign	0.90

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	0.98
dbscSNV1_RF	Benign	0.71
SpliceAI score (max)		0.76		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.76		Position offset: 4

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

Publications

LitVar

Other links and lift over

dbSNP: rs568718845; hg19: chr1-24140676;