rs62001050

Positions:

• chr5-78110280-A-G
• chr5-78110280-A-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The ENST00000255194.11(AP3B1):​c.2324T>C​(p.Ile775Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,456,806 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I775K) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: AP3B1 ENST00000255194.11 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.744

Genes affected

AP3B1 (HGNC:566): (adaptor related protein complex 3 subunit beta 1) This gene encodes a protein that may play a role in organelle biogenesis associated with melanosomes, platelet dense granules, and lysosomes. The encoded protein is part of the heterotetrameric AP-3 protein complex which interacts with the scaffolding protein clathrin. Mutations in this gene are associated with Hermansky-Pudlak syndrome type 2. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Nov 2012]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.02233082).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
AP3B1	NM_003664.5	c.2324T>C	p.Ile775Thr	missense_variant	20/27	ENST00000255194.11	NP_003655.3
AP3B1	NM_001271769.2	c.2177T>C	p.Ile726Thr	missense_variant	20/27		NP_001258698.1
AP3B1	NM_001410752.1	c.2324T>C	p.Ile775Thr	missense_variant	20/23		NP_001397681.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
AP3B1	ENST00000255194.11	c.2324T>C	p.Ile775Thr	missense_variant	20/27	1	NM_003664.5	ENSP00000255194	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000410 AC: 1 AN: 243744 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 131528

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: 0.0000337

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1456806 Hom.: 0 Cov.: 29 AF XY: 0.00000138 AC XY: 1 AN XY: 724352

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: 0.0000234

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Hermansky-Pudlak syndrome 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 18, 2021

This variant has not been reported in the literature in individuals with AP3B1-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces isoleucine with threonine at codon 775 of the AP3B1 protein (p.Ile775Thr). The isoleucine residue is weakly conserved and there is a moderate physicochemical difference between isoleucine and threonine. Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The threonine amino acid residue is found in multiple mammalian species, suggesting that this missense change does not adversely affect protein function. These predictions have not been confirmed by published functional studies and their clinical significance is uncertain. 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
AlphaMissense	Benign	0.046
BayesDel_addAF	Benign	-0.093	T
BayesDel_noAF	Benign	-0.27
CADD	Benign	6.6
DANN	Benign	0.69
DEOGEN2	Benign	0.18	T;.
Eigen	Benign	-1.2
Eigen_PC	Benign	-1.1
FATHMM_MKL	Benign	0.076	N
LIST_S2	Benign	0.36	T;T
M_CAP	Benign	0.028	D
MetaRNN	Benign	0.022	T;T
MetaSVM	Uncertain	0.12	D
MutationAssessor	Benign	0.34	N;.
MutationTaster	Benign	1.0	N;N
PrimateAI	Benign	0.26	T
PROVEAN	Benign	1.1	N;N
REVEL	Benign	0.21
Sift	Benign	0.63	T;T
Sift4G	Benign	0.72	T;T
Polyphen		0.0	B;.
Vest4		0.067
MutPred		0.27		Gain of phosphorylation at I775 (P = 0.0016);.;
MVP		0.18
MPC		0.072
ClinPred		0.018	T
GERP RS		-1.9
Varity_R		0.022
gMVP		0.043

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs62001050; hg19: chr5-77406104;