Whether it’s our personal of professional lives, we’re told time and time again that making the right connection is key. It turns out that that’s also true for our brains; making proper neuronal connections early is make or break. Altered neuronal connections can cause neurodevelopmental disorders. Often, these disorders are associated with mutations in genes with unknown or poorly described functions. These genes may be predicted to affect processes such as neuronal connectivity and lead to neurodevelopmental disorders, but actually demonstrating this is very challenging. Finding these mechanisms can lead to better understanding of the disorder, but also of neurodevelopment in general. C11orf46 encodes a small nuclear protein located in a region on chr. 11p13 linked to syndromic intellectual disability (ID). C11orf46 was recently implicated in a study identifying novel open reading frames in recessive ID, little more is known about the gene.
The labs of Schahram Akbarian (Mount Sinai) and Atsushi Kamiya (Johns Hopkins) sought to investigate the role of C11orf46 in neurodevelopment. They used magnetic resonance imaging (MRI) and cell lines from patients with deletions in the chr. 11p3 region, as well as mouse models of C11orf46 deletion. They also utilized epigenetic editing via the dCas9-SunTag system with C11orf46 effector domains to determine if they could rescue the downstream gene expression changes resulting from C11orf46knockdown. Here’s what they found:
- Knockdown of C11orf46
at mouse embryonic day 15 results in severe neuron connectivity (axonal arborization)
deficits, which are dosage dependent.
- The C11orf46 variant (the R236H mutation, which impairs the protein binding CRD domain), found in patients with neurodevelopmental disorder, does not rescue this phenotype
- Using flag-tagged C11orf46 in cell lines, the
authors found that C11orf46 predominately binds nuclear proteins, and that these
bindings are ablated by mutating the CRD domain in which variants occur in
patients with neurodevelopmental disorder.
- The SETDB1 complex, which deposits the repressive H3K9me3 mark, is a top hit.
- The R236H mutation disrupts the C11orf46 assembly with the SETDB1 complex but not its association with histone H3
- They found that many axon regulation genes were
dysregulated in cell lines in response to C11orf46 knockdown
- They targeted one such gene, Sema6a, with a dCas9-SunTag construct that utilizes an effector from wild type C11orf46 protein
- This construct reduces the expression of Sema6a to levels seen in wild-type cells, showing that C11orf46 actively represses transcribed genes
- Further, this construct rescues the impaired connectivity between brain hemispheres via repressive chromatin remodeling by the SETDB1 repressor complex
This study characterizes the previously unknown mechanisms of C11orf46’s impact on neurodevelopment. Senior author Atsushi Kamiya shares, “Although this work is early, these findings suggest that we may be able to develop future epigenome editing therapies that could help reshape the neural connections in the brain, and perhaps prevent developmental disorders of the brain from occurring.”
Engage your synaptic connections with the full story in Nature Communications, September 2019