Genetic epilepsy syndromesGene: YIF1B
AlMuhaizea et al (2020 - PMID: 32006098) report on the phenotype of 6 individuals (from 5 families) with biallelic YIF1B truncating variants.
Affected subjects presented hypotonia, failure to thrive, microcephaly (5/6), severe global DD and ID (as evident from best motor/language milestones achieved - Table S1) as well as features suggestive of a motor disorder (dystonia/spasticity/dyskinesia). Seizures were reported in 2 unrelated individuals (2/6). MRI abnormalities were observed in some with thin CC being a feature in 3.
Variable initial investigations were performed including SNP CMA, MECP2, microcephaly / neurotransmitter disorders gene panel testing did not reveal P/LP variants.
YIF1B variants were identified in 3 families within ROH. Following exome sequencing, affected individuals were found to be homozygous for truncating variants (4/5 families being consanguineous). The following 3 variants were identified (NM_001039672.2) : c.186dupT or p.Ala64fs / c.360_361insACAT or p.Gly121fs / c.598G>T or p.Glu200*.
YIF1B encodes an intracellular transmembrane protein.
It has been previously demonstrated that - similarly to other proteins of the Yip family being implicated in intracellular traffic between the Golgi - Yif1B is involved in the anterograde traffic pathway. Yif1B KO mice demonstrate a disorganized Golgi architecture in pyramidal hippocampal neurons (Alterio et al 2015 - PMID: 26077767). The rat ortholog interacts with serotonin receptor 1 (5-HT1AR) with colocalization of Yif1BB and 5-HT1AR in intermediate compartment vesicles and involvement of the former in intracellular trafficing/modulation of 5-HT1AR transport to dendrites (PMID cited: 18685031).
Available mRNA and protein expression data (Protein Atlas) suggest that the gene is widely expressed in all tissues incl. neuronal cells. Immunochemistry data from the Human Brain Atlas also suggest that YIF1B is found in vesicles and localized to the Golgi apparatus. Immunohistochemistry in normal human brain tissue (cerebral cortex) demonstrated labeling of neuronal cells (Human Protein Atlas).
Functional/network analysis of genes co-regulated with YIF1B based on available RNAseq data, suggest enrichement in in genes important for nervous system development and function.
Please consider inclusion in other panels that may be relevant (e.g. microcephaly, etc).
Created: 7 May 2020, 7:07 a.m.
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Central hypotonia; Failure to thrive; Microcephaly; Global developmental delay; Intellectual disability; Seizures; Spasticity; Abnormality of movement
gene: YIF1B was added gene: YIF1B was added to Genetic epilepsy syndromes. Sources: Literature Mode of inheritance for gene: YIF1B was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: YIF1B were set to 32006098 Phenotypes for gene: YIF1B were set to Central hypotonia; Failure to thrive; Microcephaly; Global developmental delay; Intellectual disability; Seizures; Spasticity; Abnormality of movement Penetrance for gene: YIF1B were set to Complete Review for gene: YIF1B was set to AMBER