A mutation in the Srrm4 gene causes alternative splicing defects and deafness in the Bronx waltzer mouse.
Sensory hair cells are essential for hearing and balance. Their development from epithelial precursors has been extensively characterized with respect to transcriptional regulation, but not in terms of posttranscriptional influences. Here we report on the identification and functional characterization of an alternative-splicing regulator whose inactivation is responsible for defective hair-cell development, deafness, and impaired balance in the spontaneous mutant Bronx waltzer (bv) mouse. We used positional cloning and transgenic rescue to locate the bv mutation to the splicing factor-encoding gene Ser/Arg repetitive matrix 4 (Srrm4). Transcriptome-wide analysis of pre-mRNA splicing in the sensory patches of embryonic inner ears revealed that specific alternative exons were skipped at abnormally high rates in the bv mice. Minigene experiments in a heterologous expression system confirmed that these skipped exons require Srrm4 for inclusion into the mature mRNA. Sequence analysis and mutagenesis experiments showed that the affected transcripts share a novel motif that is necessary for the Srrm4-dependent alternative splicing. Functional annotations and protein-protein interaction data indicated that the encoded proteins cluster in the secretion and neurotransmission pathways. In addition, the splicing of a few transcriptional regulators was found to be Srrm4 dependent, and several of the genes known to be targeted by these regulators were expressed at reduced levels in the bv mice. Although Srrm4 expression was detected in neural tissues as well as hair cells, analyses of the bv mouse cerebellum and neocortex failed to detect splicing defects. Our data suggest that Srrm4 function is critical in the hearing and balance organs, but not in all neural tissues. Srrm4 is the first alternative-splicing regulator to be associated with hearing, and the analysis of bv mice provides exon-level insights into hair-cell development.
Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.
Yoko
Y
Nakano
Israt
I
Jahan
Gregory
G
Bonde
Xingshen
X
Sun
Michael S
MS
Hildebrand
John F
JF
Engelhardt
Richard J H
RJ
Smith
Robert A
RA
Cornell
Bernd
B
Fritzsch
Botond
B
Bánfi
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002531:Cerebellum / Q000378:metabolism; D016000:Cluster Analysis; D003638:Deafness / Q000235:genetics*; D004195:Disease Models, Animal; D023061:Gene Order; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics*; D059372:Nucleotide Motifs; D010641:Phenotype; D012322:RNA Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome; D019076:Transgenes
D009419:Nerve Tissue Proteins; D012322:RNA Precursors; C543899:nSR100 protein, mouse