title: Alternative splicing produces high levels of noncoding isoforms of bHLH transcription factors during development.
abstract: During development, multiple cell types within a tissue often arise from a common pool of progenitor cells (PCs). PCs typically expand in number, while simultaneously producing post-mitotic cells (PMCs). This balance is partly regulated by transcription factors that are expressed within PCs, such as the basic helix-loop-helix (bHLH) gene mouse atonal homolog 7 (Math5), which is expressed in retinal PCs. Here we report that alternative splicing (AS) of Math5 serves as another layer of regulation of Math5 activity. Specifically, Math5, a single exon gene, is alternatively spliced such that the major isoform lacks the entire coding sequence. Similarly, neurogenin 3 (Ngn3), a Math5 paralog expressed in pancreatic PCs, is also alternatively spliced such that the major isoform fails to code for Ngn3 protein. The consequence of reducing the abundance of protein-coding isoforms is likely crucial, as we found that introduction of coding isoforms leads to a reduction in cycling PCs. Thus, AS can limit the number of PCs expressing key regulatory proteins that control PC expansion versus PMC production.
authors.affiliation: Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA; and Department of Ophthalmology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Rahul N
authors.initials: RN
authors.lastname: Kanadia
authors.forename: Constance L
authors.initials: CL
authors.lastname: Cepko
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle; D004622:Embryo, Mammalian / Q000378:metabolism; D005091:Exons; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D022661:RNA, Untranslated / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D022661:RNA, Untranslated; C117638:Atoh7 protein, mouse; C407737:Neurog3 protein, mouse