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| Genetic Epilepsy v0.2060 | LMNB1 | Rylee Peters reviewed gene: LMNB1: Rating: AMBER; Mode of pathogenicity: None; Publications: 32910914, 33033404; Phenotypes: Microcephaly 26, primary, autosomal dominant (MIM#619179); Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.862 | LMNB1 | Zornitza Stark Marked gene: LMNB1 as ready | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.862 | LMNB1 | Zornitza Stark Added comment: Comment when marking as ready: Note different mechanism for LMNB1-related neurodevelopmental phenotype cf Adult-onset leukodystrophy phenotype previously associated with this gene. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.862 | LMNB1 | Zornitza Stark Gene: lmnb1 has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.862 | LMNB1 | Zornitza Stark Mode of pathogenicity for gene: LMNB1 was changed from Other to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.861 | LMNB1 | Zornitza Stark Classified gene: LMNB1 as Amber List (moderate evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.861 | LMNB1 | Zornitza Stark Gene: lmnb1 has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.860 | LMNB1 | Konstantinos Varvagiannis edited their review of gene: LMNB1: Changed mode of pathogenicity: Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Genetic Epilepsy v0.860 | LMNB1 |
Konstantinos Varvagiannis gene: LMNB1 was added gene: LMNB1 was added to Genetic Epilepsy. Sources: Literature Mode of inheritance for gene: LMNB1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: LMNB1 were set to 32910914 Phenotypes for gene: LMNB1 were set to Global developmental delay; Intellectual disability; Microcephaly; Short stature; Seizures; Abnormality of the corpus callosum; Cortical gyral simplification; Feeding difficulties; Scoliosis Penetrance for gene: LMNB1 were set to unknown Mode of pathogenicity for gene: LMNB1 was set to Other Review for gene: LMNB1 was set to AMBER Added comment: Cristofoli et al (2020 - PMID: 32910914) report 7 individuals (from 5 families) harboring mostly de novo LMNB1 variants. The common phenotype consisted of primary microcephaly (7/7 ranging from -4.4 to -10 SD), DD/ID (7/7), relative short stature in most (+0.7 to -4 SD). Additional features included brain MRI abnormalities (abnormal CC in 3, simplified gyral pattern in 3, small structurally normal brain, etc), seizures (4 individuals from 2 families), limb spasticity (1/7), cortical visual impairment (in 3), feeding difficulties (5/7), scoliosis (4/7). Non-overlapping dysmorphic features were reported in some. Variants were identified by WES or custom-designed gene panel and included 3 missense variants, 1 in-frame deletion and a splice variant. The in-frame deletion was inherited from a similarly affected parent in whom the variant occurred as a dn event. The splice SNV(NM_005573.3:c.939+1G>A) occurred in 3 sibs and was present as mosaic variant (15%) in the parent. This variant was predicted to result to extension of exon 5 by 6 amino-acids (samples were unavailable for mRNA studies). LMNB1 encodes a B-type lamin (the other being encoded by LMNB2). A- and B- type lamins are major components of the nuclear lamina. As the authors comment, LMNB1 is expressed in almost all cell types beginning at the earliest stages of development. Lamin-deficient mouse models support an essential role of B-type lamins in organogenesis, neuronal migration, patterning during brain development. Functional studies performed, demonstrated impaired formation of LMNB1 nuclear lamina in LMNB1-null HeLa cells transfected with cDNAs for 3 missense variants. Two variants (Lys33Glu/Arg42Trp) were shown to result in decreased nuclear localization with increased abundance in the cytosolic fraction. In patient derived LCLs these variants led to abnormal nuclear morphology. A missense variant in another domain (Ala152Gly - 1st coil domain) resulted also in lower abundance of lamin B1, irregular lamin A/C nuclear lamina, as well as more condensed nuclei (HeLa cells). LMNB1 duplications or missense mutations increasing LMNB1 expression are associated with a different presentation of AD leuodystrophy. A variant previously associated with leukodystrophy (Arg29Trp) was shown to behave differently (present in the nuclear extract but not in the cytosol, lamin B1 to A/C ratio in nuclear extract was not significantly altered compared to wt as was the case for Arg42Trp, Lys33Glu). Given the pLI score of 0.55 as well as the phenotype of individuals with deletions (not presenting microcephaly) the authors predict that a dominant-negative effect applies (rather than haploinsufficiency). Consider inclusion in the following panels : DD/ID (green), epilepsy (amber - 4 of 7 patients belonging to 2 families), primary microcephaly (green), callosome (amber/green - 3 individuals belonging to 3 families), mendeliome (green), etc. Sources: Literature |
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