20-62821204-G-C

Variant names:

• chr20-62821204-G-C
• rs149690829
• NM_001853.4:c.333G>C

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 2P and 5B. PM2 BP4_Strong BP7

The NM_001853.4(COL9A3):​c.333G>C​(p.Pro111Pro) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,460,894 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. P111P) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: COL9A3 NM_001853.4 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: -3.30
• Publications: 0 publications found

Genes affected

COL9A3 (HGNC:2219): (collagen type IX alpha 3 chain) This gene encodes one of the three alpha chains of type IX collagen, the major collagen component of hyaline cartilage. Type IX collagen, a heterotrimeric molecule, is usually found in tissues containing type II collagen, a fibrillar collagen. Mutations in this gene are associated with multiple epiphyseal dysplasia type 3. [provided by RefSeq, Jan 2010]

COL9A3 Gene-Disease associations (from GenCC):

• epiphyseal dysplasia, multiple, 3

  Inheritance: AD Classification: DEFINITIVE, STRONG, MODERATE Submitted by: Ambry Genetics, Illumina, G2P, Labcorp Genetics (formerly Invitae)
• Stickler syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, LIMITED Submitted by: Ambry Genetics, Genomics England PanelApp, ClinGen
• Stickler syndrome, type 6

  Inheritance: AR Classification: DEFINITIVE, STRONG, LIMITED Submitted by: G2P, Ambry Genetics, Labcorp Genetics (formerly Invitae)
• multiple epiphyseal dysplasia due to collagen 9 anomaly

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• autosomal recessive Stickler syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_benign. The variant received -3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.92).
• BP7: Synonymous conserved (PhyloP=-3.3 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
COL9A3	NM_001853.4	c.333G>C	p.Pro111Pro	synonymous_variant	Exon 6 of 32	ENST00000649368.1	NP_001844.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
COL9A3	ENST00000649368.1	c.333G>C	p.Pro111Pro	synonymous_variant	Exon 6 of 32		NM_001853.4	ENSP00000496793.1
COL9A3	ENST00000452372.2	c.222G>C	p.Pro74Pro	synonymous_variant	Exon 5 of 12	5		ENSP00000394280.1
COL9A3	ENST00000477612.5	n.329G>C		non_coding_transcript_exon_variant	Exon 6 of 12	3
COL9A3	ENST00000489045.5	n.379G>C		non_coding_transcript_exon_variant	Exon 5 of 14	5

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1460894 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 726710

⚠️ 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: 33474

American (AMR) AF: 0.00 AC: 0 AN: 44676

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26126

East Asian (EAS) AF: 0.00 AC: 0 AN: 39688

South Asian (SAS) AF: 0.00 AC: 0 AN: 86194

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 52930

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5762

European-Non Finnish (NFE) AF: 0.00000450 AC: 5 AN: 1111726

Other (OTH) AF: 0.00 AC: 0 AN: 60318

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.00139817), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 33

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.92
CADD	Benign	0.075
DANN	Benign	0.39
PhyloP100		-3.3

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

Other links and lift over

dbSNP: rs149690829; hg19: chr20-61452556;