Project description:Inactivation of the minor spliceosome has been linked to microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1). To interrogate how minor intron splicing regulates cortical development, we employed Emx1-Cre to ablate Rnu11, which encodes the minor spliceosome-specific U11 small nuclear RNA (snRNA), in the developing cortex (pallium). Rnu11 cKO mice were born with microcephaly, caused by death of self-amplifying radial glial cells (RGCs). However, both intermediate progenitor cells (IPCs) and neurons were produced in the U11-null pallium. RNAseq of the pallium revealed elevated minor intron retention in the mutant, particularly in genes regulating cell cycle. Moreover, the only downregulated minor intron-containing gene (MIG) was Spc24, which regulates kinetochore assembly. These findings were consistent with the observation of fewer RGCs entering cytokinesis prior to RGC loss, underscoring the requirement of minor splicing for cell cycle progression in RGCs. Overall, we provide a potential explanation of how disruption of minor splicing might cause microcephaly in MOPD1.
Project description:Mutations in minor spliceosome components are linked to diseases such as Roifman syndrome, Lowry-Wood syndrome, and early-onset cerebellar ataxia (EOCA). Here we report that besides increased minor intron retention, Roifman syndrome and EOCA can also be characterized by elevated alternative splicing (AS) around minor introns. Consistent with the idea that the assembly/activity of the minor spliceosome informs AS in minor intron-containing genes (MIGs), inhibition of all minor spliceosome snRNAs led to upregulated AS. Notably, alternatively spliced MIG isoforms were bound to polysomes in the U11-null dorsal telencephalon, which suggested that aberrant MIG protein expression could contribute to disease pathogenesis. In agreement, expression of an aberrant isoform of the MIG Dctn3 by in utero electroporation, affected radial glial cell divisions. Finally, we show that AS around minor introns is executed by the major spliceosome and is regulated by U11-59K of the minor spliceosome, which forms exon-bridging interactions with proteins of the major spliceosome. Overall, we extend the exon-definition model to MIGs and postulate that disruptions of exon-bridging interactions might contribute to disease severity and pathogenesis.
Project description:Mutations in minor spliceosome components are linked to diseases such as Roifman syndrome, Lowry-Wood syndrome, and early-onset cerebellar ataxia (EOCA). Here we report that besides increased minor intron retention, Roifman syndrome and EOCA can also be characterized by elevated alternative splicing (AS) around minor introns. Consistent with the idea that the assembly/activity of the minor spliceosome informs AS in minor intron-containing genes (MIGs), inhibition of all minor spliceosome snRNAs led to upregulated AS. Notably, alternatively spliced MIG isoforms were bound to polysomes in the U11-null dorsal telencephalon, which suggested that aberrant MIG protein expression could contribute to disease pathogenesis. In agreement, expression of an aberrant isoform of the MIG Dctn3 by in utero electroporation, affected radial glial cell divisions. Finally, we show that AS around minor introns is executed by the major spliceosome and is regulated by U11-59K of the minor spliceosome, which forms exon-bridging interactions with proteins of the major spliceosome. Overall, we extend the exon-definition model to MIGs and postulate that disruptions of exon-bridging interactions might contribute to disease severity and pathogenesis.
