The splicing regulator Rbfox2 is required for both cerebellar development and mature motor function

Different Rbfox family members have highly similar protein sequences, especially in the RRM-type RBD (≥94% amino acid identity), and are expected to bind and regulate largely overlapping transcript sets.

“Since different Rbfox family members have highly similar protein sequences, especially in their RNA-recognition motif (RRM)-type RNA-binding domain (RBD; ≥94% amino acid identity), they are expected to bind and regulate largely overlapping sets of transcripts (Gallagher et al., 2010; Gehman et al., 2012).”

WT versus Rbfox1 or Rbfox2 KO brain exon-junction microarray studies identified only 20 and 29 Rbfox-dependent exons, respectively.

“Comparison of wild type (WT) versus Rbfox1 or Rbfox2 KO brains using exon-junction microarrays has identified multiple Rbfox-dependent exons (Gehman et al., 2012; Gehman et al., 2011). However, the number of exons identified using this approach is quite small (20 and 29 exons, respectively)”

CNS depletion of Rbfox2 causes cerebellar developmental defects.

“CNS depletion of Rbfox2 results in defects in cerebellar development (Gehman et al., 2012).”

Previous efforts lacked a genome-wide, high-resolution map of in vivo Rbfox interaction sites in the brain.

“An important piece of information missing in previous efforts toward this aim [e.g., (Fogel et al., 2012; Gehman et al., 2012; Gehman et al., 2011; Ray et al., 2013; Zhang et al., 2008)] is a genome-wide, high-resolution map ofin vivo Rbfox interaction sites in the brain.”

Together with neuro-developmental defects seen in cell cultures, animal models, and human patients with disrupted Rbfox proteins, this provides a compelling case that Rbfox proteins play critical roles in driving the global dynamic change of the developmental splicing-regulatory program.

“Combined with neuro-developmental defects observed in cell cultures (Kim et al., 2013), animal models (Gehman et al., 2012; Gehman et al., 2011; Kim et al., 2013), and human patients (Bhalla et al., 2004) where Rbfox proteins are disrupted, this presents a compelling case for Rbfox proteins playing critical roles in driving the global dynamic change of the developmentalsplicing-regulatory program.”

All three Rbfox genes are broadly expressed in the brain, with individual neuronal cell types expressing different combinations at different developmental times.

“All three Rbfox genes are broadly expressed in the brain, with individual neuronal cell types expressing different combinations at different developmental times51–55.”

Pan-neuronal Rbfox2 knockout mice show increased mortality with frequent hydrocephaly at 1 month of age.

“Pan-neuronal Rbfox2 knockout mice show increased mortality with frequent hydrocephaly at 1 month of age55.”

The pace-making defect becomes more severe in Rbfox1 heterozygous, Rbfox2-null brains (Rbfox1+/−; Rbfox2−/−).

“This pace-making defect becomes more severe in Rbfox1 heterozygous, Rbfox2-null brains (Rbfox1+/−; Rbfox2−/−)55.”

Specific depletion of Rbfox1 and Rbfox2 from mature Purkinje cells using L7(Pcp1)-Cre (L7-DKO) results in a similar pace-making phenotype and motor defects.

“Specific depletion of Rbfox1 and Rbfox2 from mature Purkinje cells after the completion of migration and development, using the L7(Pcp1)-Cre strain (L7-DKO), results in a similar pace-making phenotype and motor defects55”

Rbfox2−/− Purkinje cells form a proper layer but show decreased dendritic arborization and irregular, less frequent spontaneous action potentials.

“Rbfox2−/− Purkinje cells eventually form a proper layer, but show decreased dendritic arborization in the molecular layer, as well as irregular and less frequent spontaneous action potentials.”