Stable cell lines of human SH-SY5Y uniformly expressing wild-type or mutant-type FERM domain containing 7 gene

RBM45 is an m6A-binding protein that affects neuronal differentiation and the splicing of a subset of mRNAs

N⁶-methyladenosine (m⁶A) is deposited co-transcriptionally on thousands of cellular mRNAs and plays important roles in mRNA processing and cellular function. m⁶A is particularly abundant within the brain and is critical for neurodevelopment. However, the mechanisms through which m⁶A contributes to brain development are incompletely understood. RBM45 acts as an m⁶A-binding protein that is highly expressed during neurodevelopment. We find that RBM45 binds to thousands of cellular RNAs, predominantly within intronic regions. Rbm45 depletion disrupts the constitutive splicing of a subset of target pre-mRNAs, leading to altered mRNA and protein levels through both m⁶A-dependent and m⁶A-independent mechanisms. Finally, we find that RBM45 is necessary for neuroblastoma cell differentiation and that its depletion impacts the expression of genes involved in several neurodevelopmental signaling pathways. Altogether, our findings show a role for RBM45 in controlling mRNA processing and neuronal differentiation, mediated in part by the recognition of methylated RNA.

Choi et al. identify RBM45 as an m⁶A-binding protein enriched in the developing brain. RBM45 binds to thousands of cellular RNAs, primarily within introns, and regulates constitutive splicing of target transcripts. Loss of RBM45 causes altered expression of neurodevelopmental genes and defects in the proliferation and differentiation of neuroblastoma cells.

Nystagmus-related FRMD7 gene influences the maturation and complexities of neuronal processes in human neurons

AIMS

Idiopathic congenital nystagmus (ICN) is an oculomotor disorder caused by the defects in the ocular motor control regions of the brain. Mutations in FRMD7, a member of the FERM family of proteins, associated with cytoskeletal dynamics, are the most frequent causes of X-linked ICN. Previous studies illustrated that FRMD7 is involved in the elongation of neurites during neuronal development; however, almost all the studies were performed on mice cell models. The complexity in the human neuronal network might suggest a unique vulnerability of human neurons to FRMD7 mutations.

METHODS

Herein, we successfully established human neuronal cell models with FRMD7 mutations, from fibroblasts-reprogrammed neurons (iNs). In these neurons, the complexity of the neuronal processes was measured by the induced ratio, total neurite length, the number of terminals, and the number of maturation neurons.

RESULTS

The complexity of the neuronal processes was greatly reduced during various reprogramming stages in the presence of FRMD7 mutations. Consistently, the expression of the three main Rho GTPases was significantly increased by FRMD7 mutations. Interestingly, a slightly diverse phenotype is observed in different derived neurons.

CONCLUSION

We established ideal human neuron models and confirmed that the mutation in FRMD7 influences the maturation and complexities of neuronal processes, which might be involved with the Rho GTPase signaling.