NM_001378030.1:c.492+1G>C

Variant names:

• chr16-725236-C-G
• rs138669350
• NM_001378030.1:c.492+1G>C

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PVS1_Moderate PM2

The NM_001378030.1(CCDC78):​c.492+1G>C variant causes a splice donor, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000687 in 1,456,104 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: CCDC78 NM_001378030.1 splice_donor, intron
• Scores: Splicing: ADA: 0.9999
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -0.602
• Publications: 0 publications found

Genes affected

CCDC78 (HGNC:14153): (coiled-coil domain containing 78) Involved in de novo centriole assembly involved in multi-ciliated epithelial cell differentiation and skeletal muscle contraction. Located in several cellular components, including centriole; deuterosome; and sarcolemma. Implicated in centronuclear myopathy 4. [provided by Alliance of Genome Resources, Apr 2022]

CCDC78 Gene-Disease associations (from GenCC):

• congenital myopathy with internal nuclei and atypical cores

  Inheritance: AD Classification: SUPPORTIVE, LIMITED Submitted by: G2P, Orphanet, Labcorp Genetics (formerly Invitae)
• centronuclear myopathy

  Inheritance: AD Classification: LIMITED Submitted by: ClinGen

ACMG classification

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.040339705 fraction of the gene. No cryptic splice site detected. Exon removal is inframe change.
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CCDC78	NM_001378030.1	c.492+1G>C		splice_donor_variant, intron_variant	Intron 5 of 13	ENST00000345165.10	NP_001364959.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CCDC78	ENST00000345165.10	c.492+1G>C		splice_donor_variant, intron_variant	Intron 5 of 13	5	NM_001378030.1	ENSP00000316851.5

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 6.87e-7 AC: 1 AN: 1456104 Hom.: 0 Cov.: 37 AF XY: 0.00 AC XY: 0 AN XY: 724606

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44716

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26134

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 47762

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111944

Other (OTH) AF: 0.00 AC: 0 AN: 60342

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 34

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Benign	-0.39	T
BayesDel_noAF	Benign	-0.80
CADD	Benign	16
DANN	Benign	0.64
Eigen	Benign	0.070
Eigen_PC	Benign	-0.35
FATHMM_MKL	Benign	0.23	N
PhyloP100		-0.60
GERP RS		-0.34

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Benign	0.68
SpliceAI score (max)		0.70		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.70		Position offset: 1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs138669350; hg19: chr16-775236;