21-36756651-C-T

Variant names:

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM2PM5PP3_ModeratePP5

The NM_001352514.2(HLCS):c.2341G>A(p.Asp781Asn) variant causes a missense change. The variant allele was found at a frequency of 0.0000124 in 1,614,048 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D781E) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000039 ( 0 hom., cov: 31)

Exomes 𝑓: 0.0000096 ( 0 hom. )

Consequence

HLCS
NM_001352514.2 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2U:3

Conservation

PhyloP100: 4.16

Publications

6 publications found

Variant links:

Genes affected

HLCS (HGNC:4976): (holocarboxylase synthetase) This gene encodes an enzyme that catalyzes the binding of biotin to carboxylases and histones. The protein plays an important role in gluconeogenesis, fatty acid synthesis and branched chain amino acid catabolism. Defects in this gene are the cause of holocarboxylase synthetase deficiency. Multiple alternatively spliced variants, encoding the same protein, have been identified.[provided by RefSeq, Jun 2011]

HLCS Gene-Disease associations (from GenCC):

holocarboxylase synthetase deficiency
Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Myriad Women’s Health, Orphanet, Labcorp Genetics (formerly Invitae), G2P, ClinGen

HLCS links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PM5

Other missense variant is known to change same aminoacid residue: Variant chr21-36756651-C-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 2676009.Status of the report is criteria_provided_single_submitter, 1 stars.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.89

PP5

Variant 21-36756651-C-T is Pathogenic according to our data. Variant chr21-36756651-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 558569.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HLCS	NM_001352514.2 link	c.2341G>A	p.Asp781Asn	missense_variant	Exon 10 of 11	ENST00000674895.3	NP_001339443.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HLCS	ENST00000674895.3 link	c.2341G>A	p.Asp781Asn	missense_variant	Exon 10 of 11		NM_001352514.2	ENSP00000502087.2

Frequencies

GnomAD3 genomes

AF:

0.0000395

AC:

AN:

152046

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000242

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000197

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.000208

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000159

AC:

AN:

251496

AF XY:

0.0000147

show subpopulations

Gnomad AFR exome

AF:

0.0000615

Gnomad AMR exome

AF:

0.0000289

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000879

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000958

AC:

AN:

1461884

Hom.:

Cov.:

AF XY:

0.00000825

AC XY:

AN XY:

727244

show subpopulations

African (AFR)

AF:

0.0000299

AC:

AN:

33480

American (AMR)

AF:

0.0000671

AC:

AN:

44724

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26136

East Asian (EAS)

AF:

0.00

AC:

AN:

39700

South Asian (SAS)

AF:

0.0000116

AC:

AN:

86254

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53420

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.00000719

AC:

AN:

1112008

Other (OTH)

AF:

0.0000166

AC:

AN:

60394

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.500

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.0000394

AC:

AN:

152164

Hom.:

Cov.:

AF XY:

0.0000403

AC XY:

AN XY:

74378

show subpopulations

African (AFR)

AF:

0.0000241

AC:

AN:

41506

American (AMR)

AF:

0.000196

AC:

AN:

15282

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3470

East Asian (EAS)

AF:

0.00

AC:

AN:

5174

South Asian (SAS)

AF:

0.000208

AC:

AN:

4808

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10588

Middle Eastern (MID)

AF:

0.00

AC:

AN:

294

European-Non Finnish (NFE)

AF:

0.0000147

AC:

AN:

68018

Other (OTH)

AF:

0.00

AC:

AN:

2112

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.467

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.0265

Hom.:

2349

Bravo

AF:

0.0000416

ESP6500AA

AF:

0.000227

AC:

ESP6500EA

AF:

0.00

AC:

ExAC

AF:

0.0000247

AC:

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2Uncertain:3

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Holocarboxylase synthetase deficiency

Pathogenic:1Uncertain:2

Oct 20, 2021

Myriad Genetics, Inc.

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

NM_000411.6(HLCS):c.1900G>A(D634N) is a missense variant classified as a variant of uncertain significance in the context of holocarboxylase synthetase deficiency. D634N has been observed in cases with relevant disease (PMID: 12633764, 17274881, 16134170). Functional assessments of this variant are not available in the literature. D634N has been observed in population frequency databases (gnomAD: AFR 0.01%). In summary, there is insufficient evidence to classify NM_000411.6(HLCS):c.1900G>A(D634N) as pathogenic or benign. Please note: this variant was assessed in the context of healthy population screening. -

Oct 13, 2021

Natera, Inc.

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Feb 08, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces aspartic acid, which is acidic and polar, with asparagine, which is neutral and polar, at codon 634 of the HLCS protein (p.Asp634Asn). This variant is present in population databases (rs149399432, gnomAD 0.006%). This missense change has been observed in individual(s) with holocarboxylase synthetase deficiency (PMID: 12633764, 17274881). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 558569). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt HLCS protein function with a positive predictive value of 80%. This variant disrupts the p.Asp634 amino acid residue in HLCS. Other variant(s) that disrupt this residue have been observed in individuals with HLCS-related conditions (PMID: 11735028), which suggests that this may be a clinically significant amino acid residue. For these reasons, this variant has been classified as Pathogenic. -

not provided

Pathogenic:1

Mar 10, 2023

GeneDx

Significance:Likely pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 16134170, 25087612, 12633764, 17274881) -

not specified

Uncertain:1

Jun 12, 2025

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Variant summary: HLCS c.1900G>A (p.Asp634Asn) results in a conservative amino acid change located in the Biotinyl protein ligase (BPL) and lipoyl protein ligase (LPL), catalytic domain of the encoded protein sequence. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change. The variant allele was found at a frequency of 1.6e-05 in 251496 control chromosomes. c.1900G>A has been observed in individual(s) affected with Holocarboxylase Synthetase Deficiency. These data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 17274881, 12633764). ClinVar contains an entry for this variant (Variation ID: 558569). Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Uncertain

0.51

BayesDel_addAF

Benign

0.0068

BayesDel_noAF

Benign

-0.13

CADD

Benign

(source)

DANN

Uncertain

1.0

DEOGEN2

Uncertain

0.60

D;D;D

Eigen

Uncertain

0.34

Eigen_PC

Benign

0.19

FATHMM_MKL

Uncertain

0.80

LIST_S2

Uncertain

0.94

D;.;.

M_CAP

Uncertain

0.23

MetaRNN

Pathogenic

0.89

D;D;D

MetaSVM

Pathogenic

0.90

MutationAssessor

Pathogenic

3.1

M;M;M

PhyloP100

4.2

PrimateAI

Benign

0.44

PROVEAN

Benign

-2.3

.;N;N

REVEL

Uncertain

0.55

Sift

Uncertain

0.017

.;D;D

Sift4G

Benign

0.12

T;T;T

Polyphen

1.0

D;D;D

Vest4

0.59

MVP

0.98

MPC

0.57

ClinPred

0.71

GERP RS

4.7

Varity_R

0.14

gMVP

0.66

Mutation Taster

=75/25

polymorphism

(source)

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over