Intellectual disability - microarray and sequencing
Gene: PAN2This gene is not currently associated with a disease phenotype in OMIM, but checked PMID:35304602 to make sure it is the same gene listed in the publication as on this panel and it is, so added the gene-checked tagCreated: 16 Oct 2023, 8:06 p.m. | Last Modified: 16 Oct 2023, 8:06 p.m.
Panel Version: 5.313
The rating of this gene has been updated to Green following NHS Genomic Medicine Service approval.Created: 11 Oct 2023, 9:34 a.m. | Last Modified: 11 Oct 2023, 9:34 a.m.
Panel Version: 5.286
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
PAN2 is not associated with a phenotype in OMIM, but has a moderate association with PAN2-related neurodevelopmental disorder with multiple congenital anomalies in Gen2Phen. PMID: 29620724 reports one homozygous variant in one case and PMID: 35304602 reports a further three homozygous variants in three unrelated cases. It would appear that the syndrome associated with PAN2 variants has multiple congenital anomalies (PMID: 35304602, table 1), including intellectual disabilty ranging from mild to global developmental delay.Created: 10 Jan 2023, 3:31 p.m. | Last Modified: 10 Jan 2023, 3:31 p.m.
Panel Version: 4.42
Comment on list classification: There is enough evidence for this gene to be rated GREEN at the next major review.Created: 10 Jan 2023, 3:16 p.m. | Last Modified: 10 Jan 2023, 3:16 p.m.
Panel Version: 4.42
1.
Maddirevula et al (2018 - PMID: 29620724) first reported on the phenotype associated with biallelic pathogenic variants in PAN2.
This concerned a male (15DG2222) born to consanguineous parents and exhibiting MCA, dysmorphic features and global DD (age of 34 m). Features incl. imperforate anus, metopic craniosynostosis, scoliosis, CHD (PFO, PDA, VSD), renal anomalies (duplicated collecting system) and abnormalities of the eye (posterior embryotoxon, maculopathy).
As the other 411 individuals from the cohort, the child had 1st-tier testing genetic testing using a dysmorphology/skeletal dysplasia panel of 296 genes.
Subsequent autozygome analysis (Axiom genotyping platform) was used to identify ROH (authors state "segregating within the family", in pedigree the proband was the single affected person and single child).
WES revealed a PAN2 indel. [NM_001166279.1:c.3162delC / p.(Ser1055Profs*4)].
There were no additional studies.
Role of PAN2 and animal models discussed as below.
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2.
Reuter et al. (2022 - https://doi.org/10.1038/s41431-022-01077-y) describe the phenotype of 5 additional individuals - from 3 unrelated families (2 consanguineous) - harboring biallelic PAN2 variants. The authors review the phenotype of the previously described case.
Features included DD (6/6), ID (4/5 with relevant age in the mild-moderate range, 1/5 had borderline IF), sensorineural hearing loss (5/6) and incompletely penetrant congenital anomalies of the heart (4/6 - TOF, septal defects, Ao root dilat), urinary malformations (4/6 - hypoplasia/agenesis, anovesical fistula), ophthalmological anomalies (2/6 - Rieger, posterior embryotoxon, etc). EEG anomalies or seizures were noted in 4/6. Craniofacial feat. in >=2/6 included cleft palate/bifid uvula, ptosis, hypertelorism, abn. of the nose, low-set ears, short neck. There was no comprehensive evaluation for skeletal dysplasia despite short stature/skeletal anomalies in multiple individuals. Hematological anomalies were reported in 2, possibly explained by another concurrent diagnosis (of GSD) in one individual.
WGS was performed for 1 individual, and WES for 4 members of the 2nd family and the proband in the 3rd. ROH identified in all 3 families (1 non-consanguineous but from the same region of Italy) are mentioned in the suppl. Sanger sequencing for parents and affected/unaffected sibs was mentioned for the 2 families with solo WGS/WES. One individual had a dual - previously established - diagnosis (of SLC37A4-related GSD) not related to his NDD. There were no other candidate variants except for VUS or variants in 'genes of uncertain significance'.
The majority of mammalian mature mRNAs have polyA tails, added during RNA processing. PAN2 encodes a subunit of the Pan2-Pan3 deadenylation complex which shortens mRNA 3' polyA tails, regulating mRNA stability/translation efficiency.
Specifically Pan2 is the catalytic subunit, while the interaction with Pan3 mediates efficient mRNA binding. Deadenylation in cytoplasm is mostly carried out by the Pan2-Pan3 or Ccr4-Not compexes. While perturbations of mRNA metabolism/decay are established causes of NDD and ID. In particular, monoallelic variants in genes of Ccr4-Not complex (inc. CNOT1/2/3) already causative of NDDs.
All affected individuals were homozygous for pLoF PAN2 variants, namely (NM_001166279.2): c.2335G>T / p.(Glu779*) [Fam1], c.3408dupT / p.(Glu1137*) [Fam2], c.574-2A>G / p.? [Fam3].
Variants were absent from gnomAD (where PAN2 has a pLI:0.94, o/e:0.19).
There were no variant studies performed. The splicing variant is predicted in silico to abolish the splice-acceptor site, with in-frame skippling of ex5 which codes a repeat within the WD40 domain. Previous studies in yeast have shown that this domain is important for sensing the length of the polyA tail, with absence of this domain resulting in impaired deadenylation of 90A tails (similarly to complete Pan2 del) [cited PMID: 31104843].
Overall PAN2 loss-of-function is thought to be the underlying disease mechanism.
Partial functional redundancy of Pan2/Pan3 (initiation of deadenylation) and Ccr4-Not complexes (further shortening of polyA) is speculated to mitigate consequences of PAN2 LoF in humans.
In yeast Pan2Δ, Ccr4Δ and Pan2Δ/Ccr4Δ have been studied with more severe phenotypes in double mutants where ability to shorten mRNA polyA tails was abolished [cited PMID:11239395]. In yeast extracts lacking Pan2p and Pan3p, transcripts were polyadenylated to >90-200 adenosines [cited PMID: 9774670]
Mouse mutants (MGI:1918984) had increased heart weight, increased eosinophil cell number while homozygosity for a stopgain allele (by ENU mutagenesis) was shown to result in embyonic lethality.
Finally, given the presence of thrombocytopenia and anemia in 3 individuals (2 families) as well as the link between mRNA deadenylation and telomere disease, telomere length analyses from WGS data were performed (TelSeq/Expansion Hunter dn), but there was no evidence for telomeric shortening.
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Currently, there is no PAN2-related phenotype in OMIM/G2P/SysID/PanelApp Australia.
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Consider inclusion in the ID panel with amber rating [>3 individuals/families/variants, though variant studies not performed (NMD/splicing) and authors of 2nd study recognize possibility of additional/concurrent diagnoses in individuals from consanguineous families, possibility of missed dn variants due to singleton WGS/WES in 2 fam. Also the presumed deadenylation defect not studied to date].
Please consider adding this gene to other panels - eg. for sens. hearing loss (5/6 - 3 fam), urinary tract anomalies (4/6 - 4 fam), congenital (4/6 - 3fam), anorectal malformations (2/6 - 2 families, incl. fistula or imperforate anus), clefting (2/6 - 1 fam), hematological disorders, etc.
For the time being, not added in epilepsy panel as some individuals had only EEG anomalies, few had also clinical seizures not necessarily requiring treatment.
Sources: LiteratureCreated: 19 Mar 2022, 1:27 p.m.
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Phenotypes
Global developmental delay; Intellectual disability; Sensorineural hearing impairment; Abnormality of the genitourinary system; Abnormality of the cardiovascular system; Abnormality of blood and blood-forming tissues; EEG abnormality; Seizures; Anorectal anomaly; Abnormality of the skeletal system; Abnormality of the eye; Abnormality of head or neck
Publications
Tag gene-checked tag was added to gene: PAN2.
Tag Q1_23_promote_green was removed from gene: PAN2.
Source NHS GMS was added to PAN2. Source Expert Review Green was added to PAN2. Rating Changed from Amber List (moderate evidence) to Green List (high evidence)
Tag Q1_23_promote_green tag was added to gene: PAN2.
Gene: pan2 has been classified as Amber List (Moderate Evidence).
Publications for gene: PAN2 were set to 29620724; https://doi.org/10.1038/s41431-022-01077-y
gene: PAN2 was added gene: PAN2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PAN2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PAN2 were set to 29620724; https://doi.org/10.1038/s41431-022-01077-y Phenotypes for gene: PAN2 were set to Global developmental delay; Intellectual disability; Sensorineural hearing impairment; Abnormality of the genitourinary system; Abnormality of the cardiovascular system; Abnormality of blood and blood-forming tissues; EEG abnormality; Seizures; Anorectal anomaly; Abnormality of the skeletal system; Abnormality of the eye; Abnormality of head or neck Penetrance for gene: PAN2 were set to Complete Review for gene: PAN2 was set to AMBER