NM_007254.4:c.1029+2T>C
Variant summary
Our verdict is Uncertain significance. The variant received 3 ACMG points: 3P and 0B. PVS1_ModeratePP5
The NM_007254.4(PNKP):c.1029+2T>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 0.00178 in 1,280,492 control chromosomes in the GnomAD database, with no homozygous occurrence. 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 Conflicting classifications of pathogenicity (no stars).
Frequency
Consequence
NM_007254.4 splice_donor, intron
Scores
Clinical Significance
Conservation
Publications
- ataxia - oculomotor apraxia type 4Inheritance: AR Classification: DEFINITIVE, SUPPORTIVE Submitted by: Orphanet, G2P, Laboratory for Molecular Medicine
- microcephaly, seizures, and developmental delayInheritance: AR Classification: DEFINITIVE, STRONG Submitted by: ClinGen, Ambry Genetics, Labcorp Genetics (formerly Invitae)
- Charcot-Marie-Tooth disease type 2B2Inheritance: AR Classification: STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae)
- genetic developmental and epileptic encephalopathyInheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
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ACMG classification
Our verdict: Uncertain_significance. The variant received 3 ACMG points.
Variant Effect in Transcripts
ACMG analysis was done for transcript: NM_007254.4. 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 |
|---|---|---|---|---|---|---|---|---|---|
| PNKP | NM_007254.4 | MANE Select | c.1029+2T>C | splice_donor intron | N/A | NP_009185.2 |
Ensembl Transcripts
| Selected | Gene | Transcript | Tags | HGVSc | HGVSp | Effect | Exon Rank | Protein | UniProt |
|---|---|---|---|---|---|---|---|---|---|
| PNKP | ENST00000322344.8 | TSL:1 MANE Select | c.1029+2T>C | splice_donor intron | N/A | ENSP00000323511.2 | |||
| PNKP | ENST00000596014.5 | TSL:1 | c.1029+2T>C | splice_donor intron | N/A | ENSP00000472300.1 | |||
| PNKP | ENST00000593946.5 | TSL:1 | n.*956+2T>C | splice_donor intron | N/A | ENSP00000468896.1 |
Frequencies
GnomAD3 genomes AF: 0.00109 AC: 157AN: 144138Hom.: 0 Cov.: 32 show subpopulations
GnomAD2 exomes AF: 0.00106 AC: 158AN: 149072 AF XY: 0.00109 show subpopulations
GnomAD4 exome AF: 0.00187 AC: 2120AN: 1136252Hom.: 0 Cov.: 34 AF XY: 0.00179 AC XY: 1016AN XY: 567000 show subpopulations
Age Distribution
GnomAD4 genome AF: 0.00109 AC: 157AN: 144240Hom.: 0 Cov.: 32 AF XY: 0.00115 AC XY: 81AN XY: 70546 show subpopulations
Age Distribution
ClinVar
Submissions by phenotype
Microcephaly, seizures, and developmental delay Pathogenic:9
This variant was identified as compound heterozygous.
The c.1029+2T>C variant in PNKP has been reported in the compound heterozygous state in 4 individuals with microcephaly, seizures, and developmental delay and segregated with disease in 2 affected individuals from 2 families (Rudenskaya 2019 PMID: 31061747; Freitas 2021 PMID: 33654647; Neuser 2022 PMID: 34697416). It has also been identified in 0.2% (2099/924436) of European (non-Finnish) chromosomes by gnomAD (http://gnomad.broadinstitute.org). This variant has also been reported in ClinVar (Variation ID 206401). This variant occurs within the canonical splice site(+/- 1,2) and is predicted to cause altered splicing leading to an abnormal or absent protein. Loss of function of the PNKP gene is an established disease mechanism in autosomal recessive microcephaly, seizures, and developmental delay. RNAseq showed exon 11 skipping, which is in-frame and is predicted to escape nonsense mediated decay (NMD) (Neuser 2021 PMID: 34697416; Wai 2020 PMID: 32123317). In summary, although additional studies are required to fully establish its clinical significance, this variant meets criteria to be classified as likely pathogenic for autosomal recessive microcephaly, seizures, and developmental delay. ACMG/AMP Criteria applied: PM3_Strong, PVS1_Moderate, PP1.
The c.1029+2T>C variant is located in a canonical splice-site, and it is not predicted the protein reading frame alteration, however, occur in a critical region and the variant disrupts <10% of protein - PVS1_moderate. This sequence change has been observed in affected individual(s) and ClinVar contains an entry for this variant (Clinvar ID: 206401; PMID: 33654647, 31061747) - PS4_moderate. The variant is present at low allele frequencies population databases (rs199919568 – gnomAD 0.01089%; ABraOM 0.001281 frequency - http://abraom.ib.usp.br/) - PM2_supporting. The c.1029+2T>C was detected in trans with a pathogenic variant (PMID: 31061747; 33654647) - PM3. The variant co-segregated with disease in multiple affected family members (PMID: 31061747) - PP1. In summary, the currently available evidence indicates that the variant is likely pathogenic.
Based on the classification scheme VCGS_Germline_v1.3.5, this variant is classified as Pathogenic. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with ataxia-oculomotor apraxia 4 (MIM#616267), and microcephaly, seizures, and developmental delay (MIM#613402). (I) 0106 - This gene is associated with autosomal recessive disease. (I) 0211 - Canonical splice site variant without proven consequence on splicing (no functional evidence available). It has been suggested that this variant cases exon 11 skipping however, the relevant data was not shown (PMID: 32123317). (SP) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD (v2) <0.01 for a recessive condition (190 heterozygotes, 0 homozygotes). (SP) 0311 - Multiple alternative nucleotide changes at the same canonical splice site are present in gnomAD (v4) (highest allele count: 2 heterozygotes, 0 homozygotes. (I) 0505 - Abnormal splicing is predicted by in silico tools and affected nucleotide is highly conserved. (SP) 0704 - Another canonical splice site variant comparable to the one identified in this case has limited previous evidence for pathogenicity. A different variant in the same splice site (c.1029+1G>A) has been reported as pathogenic (ClinVar). (SP) 0801 - This variant has strong previous evidence of pathogenicity in unrelated individuals. The variant has been classified as pathogenic or likely pathogenic by multiple clinical laboratories in ClinVar and has been observed as compound heterozygous in six individuals from four families with ataxia-culomotor apraxia (PMIDs: 31061747, 33654647, 34697416). It has also been classified as a VUS or likely benign in ClinVar, but these submissions do not contain significant justification for the classification and are outweighed by the pathogenic and likely pathogenic submissions. (SP) 1205 - This variant has been shown to be maternally inherited (by trio analysis). (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign
not provided Pathogenic:8Uncertain:1
PM3, PS3_moderate, PVS1_strong
RNA studies and functional RNA analyses demonstrate a damaging effect and indicate aberrant splicing in response to c.1029+2T>C resulting predominately in skipping of exon 11, affecting the phosphatase domain and the kinase domain (PMID: 37301908, 34697416, 22508754); In silico analysis supports a deleterious effect on splicing; This variant is associated with the following publications: (PMID: 31061747, 29655203, 29720203, 29261713, 22508754, 32123317, 34697416, Fontaine2022[Preprint], 33654647, 37301908, 38523675)
PNKP: PM3:Strong, PP1:Strong, PVS1:Strong, PM2:Supporting
Ataxia - oculomotor apraxia type 4 Pathogenic:3
This variant was determined to be pathogenic according to ACMG Guidelines, 2015 [PMID:25741868].
This variant was classified as: Likely pathogenic. The following ACMG criteria were applied in classifying this variant: PVS1,PM2.
Variant summary: PNKP c.1029+2T>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. Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing and loss of PNKP function. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes a 5' splicing donor site. Two publications report experimental evidence that this variant affects mRNA splicing (Wai_2020, Oddsson_2023). The variant allele was found at a frequency of 0.0011 in 149072 control chromosomes. This frequency is not significantly higher than estimated for a pathogenic variant in PNKP causing Ataxia - oculomotor apraxia type 4 (0.0011 vs 0.0011), allowing no conclusion about variant significance. c.1029+2T>C has been reported in the literature in individuals affected with PNKP-related disorders (Coll_2017, Lindy_2018, Freitas_2021). These data indicate that the variant is likely to be associated with disease. The following publications have been ascertained in the context of this evaluation (PMID: 29261713, 33654647, 29655203, 37301908, 32123317). ClinVar contains an entry for this variant (Variation ID: 206401). Based on the evidence outlined above, the variant was classified as pathogenic.
Inborn genetic diseases Pathogenic:1
The c.1029+2T>C intronic variant results from a T to C substitution two nucleotides after exon 11 (coding exon 10) of the PNKP gene. Alterations that disrupt the canonical splice site are expected to result in aberrant splicing. A resulting transcript is predicted to be in-frame and is not expected to trigger nonsense-mediated mRNAdecay. However, the region predicted to be impacted is critical for protein function (Ambry internal data). Based on data from gnomAD, the C allele has an overall frequency of 0.106% (190/178830) total alleles studied. The highest observed frequency was 0.208% (147/70858) of European (non-Finnish) alleles. This variant has been identified in conjunction with other PNKP variants in individuals with features consistent with PNKP-related neurological disorder and segregated with disease in at least one family; in at least one instance, the variants were identified in trans (Freitas, 2021; Rudenskaya, 2019; Neuser, 2022). This nucleotide position is highly conserved in available vertebrate species. RNA studies have demonstrated that this alteration results in abnormal splicing in the set of samples tested (Oddsson, 2023; Wai, 2020; Neuser, 2022). In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Based on the available evidence, this alteration is classified as pathogenic.
Abnormal cerebral morphology Pathogenic:1
Charcot-Marie-Tooth disease type 2B2;C3150667:Microcephaly, seizures, and developmental delay;C4225397:Ataxia - oculomotor apraxia type 4 Pathogenic:1
This variant has been reported in the literature in the compound heterozygous state in at least 2 individuals with features of ataxia with oculomotor apraxia type 4 (AOA4) segregating with disease in 2 affected family members. This variant has also been identified in the heterozygous state in at least 3 individuals with epilepsy; however, at least 1 author has called into question the pathogenicity of this variant (Coll 2017 PMID:29261713, Stanek 2018 PMID:29720203, Lindy 2018 PMID:29655203, Rudenskaya 2019 PMID:310617747, Freitas 2021 PMID:33654647). This variant is present in the Genome Aggregation Database (Highest reported MAF 0.2% (127/65136) (https://gnomad.broadinstitute.org/variant/19-49862369-A-G?dataset=gnomad_r3). This variant is present in ClinVar, with several labs classifying this variant as Pathogenic or Likely Pathogenic; however, at least 1 laboratory has submitted a classification of Likely Benign for this variant (Variation ID:206401). Evolutionary conservation and computational predictive tools for this variant are limited or unavailable. RNA studies predict that this variant will impact the protein with altered splicing (Wai 2020 PMID:32123317). However, these studies may not accurately represent in vivo biological function. Of note, this variant alters the consensus splice sequence (+/- 1,2) which is predicted to result in an absent or abnormal protein. Loss of function variants are a known mechanism of disease for this gene (Dumitrache 2017 PMID:27125728). However, this variant is expected to alter exon 11; this exon is in frame and represents less than 10% of the total protein. In summary, data on this variant is highly suspicious for disease, but requires further evidence for pathogenicity. Therefore, this variant is classified as likely pathogenic.
Developmental and epileptic encephalopathy, 12 Pathogenic:1
This sequence change affects a donor splice site in intron 11 of the PNKP gene. RNA analysis indicates that disruption of this splice site induces altered splicing and may result in an absent or altered protein product. This variant is present in population databases (rs199919568, gnomAD 0.2%), and has an allele count higher than expected for a pathogenic variant. Disruption of this splice site has been observed in individual(s) with clinical features of PNKP-related conditions (PMID: 31061747). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 206401). Studies have shown that disruption of this splice site results in skipping of exon 11 and/or intron 10 retention , and produces a non-functional protein and/or introduces a premature termination codon (PMID: 34697416, 37301908). For these reasons, this variant has been classified as Pathogenic.
Microcephaly, seizures, and developmental delay;C4225397:Ataxia - oculomotor apraxia type 4 Pathogenic:1
not specified Uncertain:1
Variant classified as Uncertain Significance - Favor Pathogenic. The c.1029+2T>C variant in PNKP has been reported in the compound heterozygous state in one individual with Ataxia with Oculomotor Apraxia Type 4 and their affected sibling (Rudenskaya 2019 PMID: 31061747). It has also been identified in 3 individuals with epilepsy (Lindy 2018 PMID: 29655203, Stanek 2018 PMID: 29720203, Coll 2017 PMID: 29261713). It has also been reported by other clinical laboratories in ClinVar (Variation ID:206401) and has been identified in 0.2% (147/70858) of European chromosomes by gnomAD (http://gnomad.broadinstitute.org). This variant occurs within the canonical splice site (+/- 1,2) and is predicted to cause altered splicing leading to an abnormal or absent protein. However, exon 11, which is affected by this variant, is in frame and consists of only 93 base pairs and encodes less than 10% of the PNKP protein. The PNKP gene has been definitively been associated with autosomal recessive ataxia with oculomotor apraxia and with microcephaly, seizures, and developmental delay. However, there is limited evidence regarding its association with epilepsy. In summary, while there is some suspicion for a pathogenic role, the clinical significance of this variant is uncertain for autosomal recessive ataxia with oculomotor apraxia. ACMG/AMP Criteria applied: PVS1_Moderate, PM3, PP1_Supporting.
Microcephaly Uncertain:1
PNKP-related disorder Uncertain:1
The PNKP c.1029+2T>C variant is predicted to disrupt the GT donor site and interfere with normal splicing. This variant has been reported in the compound heterozygous state in at least five individuals with severe progressive microcephaly, hypotonia, developmental delays, and ataxia-oculomotor apraxia type 4 (Neuser et al. 2021. PubMed ID: 34697416; Rudenskaya et al. 2019. PubMed ID: 31061747; Freitas et al. 2021. PubMed ID: 33654647). Functional studies confirm that this variant causes aberrant splicing by skipping exon 11, resulting in an in-frame deletion of amino acids 313-343 (Wai et al. 2020. PubMed ID: 32123317). This variant is reported in 0.21% of alleles in individuals of European (Non-Finnish) descent in gnomAD and has conflicting interpretations regarding it pathogenicity in ClinVar, ranging from pathogenic to likely pathogenic to uncertain significance to likely benign (https://www.ncbi.nlm.nih.gov/clinvar/variation/206401/). Loss of function is a known mechanism of disease for PNKP, and other splice altering changes have been reported as causative; however these other pathogenic variants are all found at lower frequency in gnomAD (Human Gene Mutation Database). Although we suspect that this variant may be pathogenic, at this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence.
Computational scores
Source:
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at