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| Intellectual disability - microarray and sequencing v3.0 | MN1 |
Konstantinos Varvagiannis gene: MN1 was added gene: MN1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MN1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MN1 were set to 31834374; 31839203; 15870292 Phenotypes for gene: MN1 were set to Central hypotonia; Feeding difficulties; Global developmental delay; Intellectual disability; Hearing impairment; Abnormality of facial skeleton; Craniosynostosis; Abnormality of the face; Abnormality of the cerebellum; Abnormality of the corpus callosum; Polymicrogyria Penetrance for gene: MN1 were set to Complete Review for gene: MN1 was set to GREEN Added comment: Two studies by Mak et al (2019 - PMID: 31834374 / Ref1) and Miyake et al (2019 - PMID: 31839203 / Ref2) provide sufficient evidence for heterozygous MN1 C-terminal truncating variants (predicted to escape NMD - localizing within the last nucleotides of exon 1 or in exon 2) being associated with a distinctive phenotype and DD and ID among the features. Mak et al also discuss on the phenotype of individuals with variants causing N-terminal truncation or with MN1 deletions (discussed at the end of this review). Overlapping features for C-terminal truncating variants included hypotonia, feeding difficulties, global DD and ID, hearing loss, cranial shape defects (/craniosynostosis in few), highly suggestive/distinctive facial features (eg. frontal bossing, hypertelorism, downslanting palpebral-fissures, shallow orbits, short upturned nose, low-set/posteriorly rotated/dysplastic ears, etc) and brain MRI abnormalities (eg. rhomboencephalosynapsis or cerebellar dysplasia, polymicrogyria, dysplastic CC). The majority of the affected individuals were investigated by WES/WGS with a single one tested by targeted MN1 Sanger sequencing due to highly suggestive features. Variable previous investigations incl. CMA in several, gene panel testing (Rasopathies, hearing loss, craniofacial panels, FMR1, etc) and metabolic work were normal in most. In a single case a likely pathogenic ACSL4 also explained part of the phenotype (Ref2). In the majority of these individuals, the variant had occured as a de novo event. Two sibs had inherited the truncating variant from a milder affected mosaic parent. A parental sample was not available for an additional individual. p.(Arg1295*) or NM_002430.2:c.3883C>T was a recurrent variant, seen in several individuals and in both studies. Several lines of evidence are provided for the MN1 variants and the role of the gene including: - For few individuals for whom cell lines were available, variants were shown to escape NMD by cDNA/RT-PCR/RNA-seq [Ref1 & 2]. - The gene has a high expression in fetal brain [Ref2 / fig S2] - MN1 (* 156100 - MN1 protooncogene, transcriptional regulator) has been proposed to play a role in cell proliferation and shown to act as transcription cofactor (increasing its transactivation capacity in synergy with coactivators EP300 and RAC3) [Discussion and Refs provided in Ref2]. - In vitro studies suggested increased protein stability (upon transfection of wt/mut constructs in HEK293T cells), enhanced MN1 aggregation in nuclei (when wt/mut GFP-tagged MN1 was expressed in HeLa cells), increased inhibitory effect on cell growth (MG63 cells - role of MN1 in cell proliferation discussed above) and retained transactivation activity (upon transient MN1 overexpression of wt/mt MN1 in HEK293T cells) for the variants. These seem to support a gain-of-function effect for the C-terminal truncating variants [Ref2]. - The truncating variants are proposed to raise the fraction of Intrinsically disordered regions (IDRs = regions without fixed tertiary structure) probably contributing to the above effects [Ref2]. - Expression of FLAG-tagged MN1 wt/mut MN1 followed by immunoprecipitation and mass spectrometry analysis (mCAT-Hela cells), provided evidence that MN1 is involved in transcriptional regulation: a. through binding ZBTB24 and RING1 E3 ubiquitin ligase (with mutant MN1 displaying impaired interaction with ZBTB24 and no binding to RING1) and/or b. through interaction with DNA-binding transcription factors PBX1 and PKNOX1. Proper MN1 degradation is proposed to mediate precise transcriptional regulation. [Ref2] - Transcriptome analysis in LCLs from an affected individual suggested dysregulation of genes relevant to neuronal development (eg. LAMP, ITGA, etc) and GO analysis suggested enrichment for pathways possibly linked to the observed phenotypes [Ref2]. - Discussed in both Refs1/2, homozygous Mn1-ko mice display abnormal skull bone development and die at/shortly after birth as a result of cleft palate. Heterozygous Mn1-ko mice display hypoplastic membranous bones of the cranial skeleton and cleft palate (CP), the latter with incomplete penetrance [Meester-Smoor et al 2005 - PMID: 15870292]. This is thus compatible with the cranial shape defects observed in C-terminal truncations (while CP has been reported in gene deletions, bifid uvula was reported once in C-terminal and N-terminal truncating variants, in the latter case with submucous CP). ----- The phenotype of other MN1 variants is discussed by Mak et al (Ref1) : - 3 individuals with MN1 N-terminal truncating variants (eg. Ser179*, Pro365Thrfs*120, Ser472*) presented speech delay, mild conductive hearing loss and facial features different from C-terminal truncations. None of these individuals had significant ID. - Microdeletions: One individual (#27) with 130 kb deletion harboring only MN1, presented microcephaly, DD and ID and mildly dysmorphic facial features. Deletions spanning MN1 and other genes (eg a 1.17 Mb deletion in ind. #28) and relevant cases from the literature reviewed, with mild DD/ID, variable palatal defects and/or facial dysmorphisms (distinct from the C-terminal truncating variants) among the frequent findings. [Please consider inclusion in other possibly relevant gene panels eg. for hearing loss (conductive/sensorineural in 16/20 reported by Mak et al) or craniosynostosis, etc]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.649 | PBX1 | Eleanor Williams Publications for gene: PBX1 were set to 28566479, 29036646 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.648 | PBX1 | Eleanor Williams Classified gene: PBX1 as Green List (high evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.648 | PBX1 | Eleanor Williams Added comment: Comment on list classification: More than 3 cases where patients show developmental delay as part of the phenotype. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.648 | PBX1 | Eleanor Williams Gene: pbx1 has been classified as Green List (High Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.647 | PBX1 | Eleanor Williams commented on gene: PBX1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.579 | PBX1 | Konstantinos Varvagiannis reviewed gene: PBX1: Rating: GREEN; Mode of pathogenicity: None; Publications: 28270404, 28566479, 29036646; Phenotypes: ; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown; Current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.579 | PBX1 | Konstantinos Varvagiannis Deleted their review | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.579 | PBX1 | Konstantinos Varvagiannis reviewed gene: PBX1: Rating: GREEN; Mode of pathogenicity: None; Publications: 28270404, 28566479, 29036646; Phenotypes: ; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown; Current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.468 | PBX1 | Louise Daugherty Source Victorian Clinical Genetics Services was added to PBX1. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | PBX1 | Zornitza Stark Added gene to panel | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||