chr7-87439761-G-T

Position:

• chr7-87439761-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP2 PP3_Strong

The NM_000443.4(ABCB4):​c.1637C>A​(p.Ala546Asp) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000752 in 1,461,876 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000075 (0 hom.)
• Consequence: ABCB4 NM_000443.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts P:1 U:3
• Conservation: PhyloP100: 8.10

Genes affected

ABCB4 (HGNC:45): (ATP binding cassette subfamily B member 4) The membrane-associated protein encoded by this gene is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the MDR/TAP subfamily. Members of the MDR/TAP subfamily are involved in multidrug resistance as well as antigen presentation. This gene encodes a full transporter and member of the p-glycoprotein family of membrane proteins with phosphatidylcholine as its substrate. The function of this protein has not yet been determined; however, it may involve transport of phospholipids from liver hepatocytes into bile. Alternative splicing of this gene results in several products of undetermined function. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a helix (size 12) in uniprot entity MDR3_HUMAN there are 6 pathogenic changes around while only 0 benign (100%) in NM_000443.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), ABCB4. . Gene score misZ 1.9749 (greater than the threshold 3.09). Trascript score misZ 3.5425 (greater than threshold 3.09). GenCC has associacion of gene with pancreatitis, low phospholipid associated cholelithiasis, progressive familial intrahepatic cholestasis type 3.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.985

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
ABCB4	NM_000443.4	c.1637C>A	p.Ala546Asp	missense_variant	14/28	ENST00000649586.2	NP_000434.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
ABCB4	ENST00000649586.2	c.1637C>A	p.Ala546Asp	missense_variant	14/28		NM_000443.4	ENSP00000496956	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251282 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135794

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: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000752 AC: 11 AN: 1461876 Hom.: 0 Cov.: 32 AF XY: 0.00000688 AC XY: 5 AN XY: 727242

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: 0.00000989

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cholestasis, intrahepatic, of pregnancy, 3 Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

May 01, 2000

- -

ABCB4-related disorder Uncertain:1

Uncertain significance, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Apr 10, 2024

The ABCB4 c.1637C>A variant is predicted to result in the amino acid substitution p.Ala546Asp. This variant has been reported in the heterozygous state in a patient with intrahepatic cholestasis of pregnancy (Dixon et al. 2000. PubMed ID: 10767346). Functional studies indicate the p.Ala546Asp variant disrupts protein trafficking, resulting in a lack of functional protein at the cell surface (Dixon et al. 2000. PubMed ID: 10767346). This variant was also seen as compound heterozygous in one individual from a study of children with monogenic cholestasis (Hertel et al. 2021. PubMed ID: 34016879). This variant is reported in 0.00088% of alleles in individuals of European (Non-Finnish) descent in gnomAD. At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Dec 20, 2022

Variant summary: ABCB4 c.1637C>A (p.Ala546Asp) results in a non-conservative amino acid change located in the ABC transporter-like, ATP-binding domain (IPR003439) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-06 in 251282 control chromosomes. c.1637C>A has been reported in the literature as a heterozygous genotype (second allele not specified) in one individual with Intrahepatic Cholestasis of Pregnancy (example Dixon_2000) who has been cited by others and as a presumed compound heterozygous genotype (phase not specified) in at-least one individual with Progressive familial intrahepatic cholestasis type 3 (PFIC3) (example, Sticova_2020 cited in Hertel_2021). These data do not allow any conclusion about variant significance. At least one publication reports experimental evidence evaluating an impact on protein function (example Dixon_2000). The most pronounced variant effect results in reduced cell surface expression, abnormal protein glycosylation and abnormal trafficking of the mutant to plasma membrane, but not its activity. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation and classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Eurofins Ntd Llc (ga)

Jul 30, 2018

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.52	D
BayesDel_noAF	Pathogenic	0.51
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	.;.;D;.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.96	.;D;D;D;.
M_CAP	Pathogenic	0.75	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.5	H;H;H;H;H
MutationTaster	Benign	1.0	A;A;A;A;A
PrimateAI	Pathogenic	0.85	D
PROVEAN	Pathogenic	-5.4	.;D;D;D;D
REVEL	Pathogenic	0.94
Sift	Pathogenic	0.0	.;D;D;D;D
Sift4G	Pathogenic	0.0	.;D;D;D;D
Polyphen		1.0	D;.;D;D;.
Vest4		0.99, 0.97, 0.99, 0.99
MutPred		0.89		Loss of MoRF binding (P = 0.0522);Loss of MoRF binding (P = 0.0522);Loss of MoRF binding (P = 0.0522);Loss of MoRF binding (P = 0.0522);Loss of MoRF binding (P = 0.0522);
MVP		0.96
MPC		1.2
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.99
gMVP		0.99

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

LitVar

Other links and lift over

dbSNP: rs121918441; hg19: chr7-87069077; COSMIC: COSV55939902;