chr15-72731423-G-T

Position:

• chr15-72731423-G-T

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM2 PP3_Moderate PP5_Moderate

The NM_033028.5(BBS4):​c.830G>T​(p.Gly277Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,888 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 Likely pathogenic (★).

• Frequency:
  • Genomes: not found (cov: 29)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: BBS4 NM_033028.5 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.83

Genes affected

BBS4 (HGNC:969): (Bardet-Biedl syndrome 4) This gene is a member of the Bardet-Biedl syndrome (BBS) gene family. Bardet-Biedl syndrome is an autosomal recessive disorder characterized by severe pigmentary retinopathy, obesity, polydactyly, renal malformation and cognitive disability. The proteins encoded by BBS gene family members are structurally diverse. The similar phenotypes exhibited by mutations in BBS gene family members are likely due to the protein's shared roles in cilia formation and function. Many BBS proteins localize to the basal bodies, ciliary axonemes, and pericentriolar regions of cells. BBS proteins may also be involved in intracellular trafficking via microtubule-related transport. The protein encoded by this gene has sequence similarity to O-linked N-acetylglucosamine (O-GlcNAc) transferases in plants and archaebacteria and in human forms a multi-protein "BBSome" complex with seven other BBS proteins. Alternate splicing results in multiple transcript variants. [provided by RefSeq, Mar 2016]

BBS4 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.919
• PP5: Variant 15-72731423-G-T is Pathogenic according to our data. Variant chr15-72731423-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 412297.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BBS4	NM_033028.5	c.830G>T	p.Gly277Val	missense_variant	11/16	ENST00000268057.9	NP_149017.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BBS4	ENST00000268057.9	c.830G>T	p.Gly277Val	missense_variant	11/16	1	NM_033028.5	ENSP00000268057.4

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251488 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135918

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461888 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727244

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 29

Bravo AF: 0.00000378

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Bardet-Biedl syndrome Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 14, 2018

This sequence change replaces glycine with valine at codon 277 of the BBS4 protein (p.Gly277Val). The glycine residue is highly conserved and there is a moderate physicochemical difference between glycine and valine. This variant is present in population databases (rs749017489, ExAC 0.009%). This variant has been observed in individuals with clinical features consistent with Bardet-Biedl syndrome (Invitae). It has also been observed to segregate with Bardet-Biedl syndrome in a family (Invitae). ClinVar contains an entry for this variant (Variation ID: 412297). Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). The observation of one or more missense substitutions at this codon (p.Gly277Arg) in affected individuals suggests that this may be a clinically significant residue (PMID: 24849935). In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.39	D
BayesDel_noAF	Pathogenic	0.40
CADD	Pathogenic	30
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.90	.;D;.
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.97
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.98	D;D;D
M_CAP	Uncertain	0.14	D
MetaRNN	Pathogenic	0.92	D;D;D
MetaSVM	Uncertain	0.75	D
MutationAssessor	Pathogenic	3.5	.;H;.
PrimateAI	Pathogenic	0.88	D
PROVEAN	Pathogenic	-7.2	.;D;D
REVEL	Pathogenic	0.92
Sift	Uncertain	0.0020	.;D;D
Sift4G	Uncertain	0.0050	D;D;D
Polyphen		1.0	.;D;.
Vest4		0.96
MutPred		0.74		.;Gain of catalytic residue at G277 (P = 0.0513);.;
MVP		0.94
MPC		0.085
ClinPred		0.98	D
GERP RS		5.8
Varity_R		0.98
gMVP		0.93

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: rs749017489; hg19: chr15-73023764;