RESUMO
Mutations in RNA-binding proteins can lead to pleiotropic phenotypes including craniofacial, skeletal, limb, and neurological symptoms. Heterogeneous nuclear ribonucleoproteins (hnRNPs) are involved in nucleic acid binding, transcription, and splicing through direct binding to DNA and RNA, or through interaction with other proteins in the spliceosome. We show a developmental role for Hnrnpul1 in zebrafish, resulting in reduced body and fin growth and missing bones. Defects in craniofacial tendon growth and adult-onset caudal scoliosis are also seen. We demonstrate a role for Hnrnpul1 in alternative splicing and transcriptional regulation using RNA-sequencing, particularly of genes involved in translation, ubiquitination, and DNA damage. Given its cross-species conservation and role in splicing, it would not be surprising if it had a role in human development. Whole-exome sequencing detected a homozygous frameshift variant in HNRNPUL1 in 2 siblings with congenital limb malformations, which is a candidate gene for their limb malformations. Zebrafish Hnrnpul1 mutants suggest an important developmental role of hnRNPUL1 and provide motivation for exploring the potential conservation of ancient regulatory circuits involving hnRNPUL1 in human development.
Assuntos
Splicing de RNA , Peixe-Zebra , Processamento Alternativo , Animais , Ribonucleoproteínas Nucleares Heterogêneas/genética , RNA/metabolismo , Splicing de RNA/genética , Peixe-Zebra/genética , Peixe-Zebra/metabolismoRESUMO
The vasculature tailors to the needs of different tissues and organs. Molecular, structural, and functional specializations are observed in different vascular beds, but few genetic models give insight into how these differences arise. We identify a unique cerebrovascular mutation in the zebrafish affecting the integrity of blood vessels supplying the brain. The zebrafish bubblehead (bbh) mutant exhibits hydrocephalus and severe cranial hemorrhage during early embryogenesis, whereas blood vessels in other regions of the embryo appear intact. Here we show that hemorrhages are associated with poor cerebral endothelial-mesenchymal contacts and an immature vascular pattern in the head. Positional cloning of bbh reveals a hypomorphic mutation in betaPix, a binding partner for the p21-activated kinase (Pak) and a guanine nucleotide exchange factor for Rac and Cdc42. betaPix is broadly expressed during embryonic development and is enriched in the brain and in large blood vessels. By knockdown of specific betaPix splice variants, we show that they play unique roles in embryonic vascular stabilization or hydrocephalus. Finally, we show that Pak2a signaling is downstream of betaPix. These data identify an essential in vivo role for betaPix and Pak2a during embryonic development and illuminate a previously unrecognized pathway specifically involved in cerebrovascular stabilization.
Assuntos
Proteínas de Ciclo Celular/genética , Circulação Cerebrovascular/fisiologia , Fatores de Troca do Nucleotídeo Guanina/genética , Proteínas Serina-Treonina Quinases/fisiologia , Proteínas de Peixe-Zebra/fisiologia , Processamento Alternativo , Animais , Vasos Sanguíneos/fisiologia , Encéfalo/patologia , Hemorragia Cerebral/genética , Mapeamento Cromossômico , Clonagem Molecular , Endotélio Vascular/fisiologia , Etilnitrosoureia , Éxons , Variação Genética , Fatores de Troca do Nucleotídeo Guanina/deficiência , Dados de Sequência Molecular , Fatores de Troca de Nucleotídeo Guanina Rho , Peixe-Zebra , Proteínas de Peixe-Zebra/genética , Quinases Ativadas por p21RESUMO
Major vessels of the vertebrate circulatory system display evolutionarily conserved and reproducible anatomy, but the cues guiding this stereotypic patterning remain obscure. In the nervous system, axonal pathways are shaped by repulsive cues provided by ligands of the semaphorin family that are sensed by migrating neuronal growth cones through plexin receptors. We show that proper blood vessel pathfinding requires the endothelial receptor PlexinD1 and semaphorin signals, and we identify mutations in plexinD1 in the zebrafish vascular patterning mutant out of bounds. These results reveal the fundamental conservation of repulsive patterning mechanisms between axonal migration in the central nervous system and vascular endothelium during angiogenesis.
