16-75545825-C-G

Variant names:

• chr16-75545825-C-G
• rs1415483600
• NM_001077418.3:c.438+1G>C

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1_Strong PP5_Very_Strong

The NM_001077418.3(TMEM231):​c.438+1G>C variant causes a splice donor, intron change. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 13)
• Consequence: TMEM231 NM_001077418.3 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 7.11
• Publications: 0 publications found

Genes affected

TMEM231 (HGNC:37234): (transmembrane protein 231) This gene encodes a transmembrane protein, which is a component of the B9 complex involved in the formation of the diffusion barrier between the cilia and plasma membrane. Mutations in this gene cause Joubert syndrome (JBTS). Multiple alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Jan 2013]

TMEM231 Gene-Disease associations (from GenCC):

• ciliopathy

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• Joubert syndrome 20

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: G2P, Labcorp Genetics (formerly Invitae)
• Joubert syndrome with oculorenal defect

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Meckel syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• orofaciodigital syndrome III

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ENSG00000259992 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.13564669 fraction of the gene. Cryptic splice site detected, with MaxEntScore 4.5, offset of -38, new splice context is: tcgGTgtgc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PP5: Variant 16-75545825-C-G is Pathogenic according to our data. Variant chr16-75545825-C-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 1192252.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001077418.3. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TMEM231	NM_001077418.3	MANE Select	c.438+1G>C		splice_donor intron	N/A	NP_001070886.1
	TMEM231	NM_001077416.2		c.597+1G>C		splice_donor intron	N/A	NP_001070884.2
	TMEM231	NR_074083.2		n.604+1G>C		splice_donor intron	N/A

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TMEM231	ENST00000258173.11	TSL:1 MANE Select	c.438+1G>C		splice_donor intron	N/A	ENSP00000258173.5
	TMEM231	ENST00000568377.5	TSL:1	c.525+1G>C		splice_donor intron	N/A	ENSP00000476267.1
	TMEM231	ENST00000565067.5	TSL:5	c.438+1G>C		splice_donor intron	N/A	ENSP00000457254.1

Frequencies

GnomAD3 genomes Cov.: 13

GnomAD4 exome Cov.: 15

GnomAD4 genome Cov.: 13

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Joubert syndrome 20;C3809352:Meckel syndrome, type 11 Pathogenic:1

May 23, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects a donor splice site in intron 2 of the TMEM231 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in TMEM231 are known to be pathogenic (PMID: 23012439, 23349226). This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individual(s) with clinical features of Joubert syndrome (PMID: 32055034, 32386258). ClinVar contains an entry for this variant (Variation ID: 1192252). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic.

Joubert syndrome and related disorders Pathogenic:1

Jul 26, 2021

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: TMEM231 c.597+1G>C is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes a 5 prime splicing donor site. However, these predictions have yet to be confirmed by functional studies. The variant was absent in 100746 control chromosomes. To our knowledge, no occurrence of c.597+1G>C in individuals affected with Joubert Syndrome And Related Disorders and no experimental evidence demonstrating its impact on protein function have been reported. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as likely pathogenic.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.62	D
BayesDel_noAF	Pathogenic	0.22
CADD	Pathogenic	33
DANN	Uncertain	0.99
Eigen	Pathogenic	0.93
Eigen_PC	Pathogenic	0.72
FATHMM_MKL	Pathogenic	0.99	D
PhyloP100		7.1
GERP RS		3.8
Mutation Taster		=1/99	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.97		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.97		Position offset: 1

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

Other links and lift over

dbSNP: rs1415483600; hg19: chr16-75579723;