rs387907321

Positions:

• chr14-91272869-CCT-C

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_Moderate PM2 PP5_Moderate

The NM_001080414.4(CCDC88C):​c.5841_5842del​(p.Glu1949GlyfsTer26) variant causes a frameshift change. The variant allele was found at a frequency of 0.00000657 in 152,236 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★). Synonymous variant affecting the same amino acid position (i.e. S1947S) has been classified as Likely benign.

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: CCDC88C NM_001080414.4 frameshift
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 3.80

Genes affected

CCDC88C (HGNC:19967): (coiled-coil domain containing 88C) This gene encodes a ubiquitously expressed coiled-coil domain-containing protein that interacts with the dishevelled protein and is a negative regulator of the Wnt signalling pathway. The protein encoded by this gene has a PDZ-domain binding motif in its C-terminus with which it interacts with the dishevelled protein. Dishevelled is a scaffold protein involved in the regulation of the Wnt signaling pathway. The Wnt signaling pathway plays an important role in embryonic development, tissue maintenance, and cancer progression. Mutations in this gene cause autosomal recessive, primary non-syndromic congenital hydrocephalus; a condition characterized by excessive accumulation of cerebrospinal fluid in the ventricles of the brain. [provided by RefSeq, Jan 2013]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0404 CDS is truncated, and there are 0 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 14-91272869-CCT-C is Pathogenic according to our data. Variant chr14-91272869-CCT-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 39862.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CCDC88C	NM_001080414.4	c.5841_5842del	p.Glu1949GlyfsTer26	frameshift_variant	30/30	ENST00000389857.11
CCDC88C	XM_011536796.3	c.5733_5734del	p.Glu1913GlyfsTer26	frameshift_variant	30/30
CCDC88C	XM_047431418.1	c.5574_5575del	p.Glu1860GlyfsTer26	frameshift_variant	27/27

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CCDC88C	ENST00000389857.11	c.5841_5842del	p.Glu1949GlyfsTer26	frameshift_variant	30/30	5	NM_001080414.4	P1
CCDC88C	ENST00000556726.5	c.*1675_*1676del		3_prime_UTR_variant	7/7	5

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152236 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00316

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152236 Hom.: 0 Cov.: 32 AF XY: 0.0000134 AC XY: 1 AN XY: 74378

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000712 Hom.: 0

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Hydrocephalus, nonsyndromic, autosomal recessive 1 Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Nov 01, 2012

- -

Congenital hydrocephalus Pathogenic:1

Likely pathogenic, criteria provided, single submitter

curation

Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard

Jan 25, 2023

The homozygous p.Glu1949GlyfsTer26 variant in CCDC88C was identified by our study in one individual with congenital hydrocephalus, global developmental delay, and seizures. The p.Glu1949GlyfsTer26 variant in CCDC88C has been previously reported in five affected siblings from one family with congenital hydrocephalus 1 (PMID: 23042809), but has been identified in 0.008% (1/125568) chromosomes by TopMed (https://bravo.sph.umich.edu/, dbSNP ID: rs387907321). Although this variant has been seen in the general population in a heterozygous state, its frequency is low enough to be consistent with a recessive carrier frequency. These affected individuals (PMID: 23042809) and the individual identified by our study were homozygotes, which increases the likelihood that the p.Glu1949GlyfsTer26 variant is pathogenic. This variant has also been reported in ClinVar (Variation ID: 39862) and has been interpreted as pathogenic by OMIM. This variant is predicted to cause a frameshift, which alters the protein’s amino acid sequence beginning at position 1393 and leads to a premature termination codon 19 amino acids downstream. This termination codon occurs within the terminal 50 bases of the last exon and is more likely to escape nonsense mediated decay (NMD) and result in a truncated protein. Loss of function of the CCDC88C gene is strongly associated to autosomal recessive congenital hydrocephalus 1. In summary, although additional studies are required to fully establish its clinical significance, this variant is likely pathogenic for autosomal recessive congenital hydrocephalus 1. ACMG/AMP Criteria applied: PVS1_Supporting, PM2_Supporting, PM3, PP1_Strong (Richards 2015). -

Computational scores

Source: dbNSFP v4.3

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: rs387907321; hg19: chr14-91739213;