title: Zebrafish foggy/spt 5 is required for migration of facial branchiomotor neurons but not for their survival.
abstract: Transcript elongation is a critical step in the production of mature messenger RNAs. Many factors have been identified that are required for transcript elongation, including Spt 5. Studies in yeast determined that spt 5 is required for cell viability, and analyses in Drosophila indicate Spt 5 is localized to sites of active transcription, suggesting it is required generally for transcription. However, the requirement for spt 5 for cell viability in a metazoan organism has not been addressed. We determined that zebrafish foggy/spt 5 is required cell-autonomously for the posterior migration of facial branchiomotor neurons from rhombomere 4 (r4) into r6 and r7 of the hindbrain. These genetic mosaics also give us the unique opportunity to determine whether spt 5 is required for mRNA transcription equivalently at all loci by addressing two processes within the same cell-neuronal migration and cell viability. In a wild-type host, spt 5 null facial branchiomotor neurons survive to at least 5 days postfertilization while failing to migrate posteriorly. This finding indicates that spt 5-dependent transcript elongation is required cell-autonomously for a complex cell migration but not for the survival of these same cells. This work provides evidence that transcript elongation is not a global mechanism equivalently required by all loci and may actually be under more strict developmental regulation.
authors.affiliation: HHMI, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Cooper
authors.forename: Juli
authors.initials: J
authors.lastname: Armstrong
authors.forename: Cecilia B
authors.initials: CB
authors.lastname: Moens
mesh_terms: D000818:Animals; D001483:Base Sequence; D002465:Cell Movement; D002470:Cell Survival; D004268:DNA-Binding Proteins; D005145:Face / Q000196:embryology; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000166:cytology* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C416949:supt5h protein, zebrafish