RESUMO
Genetic factors underlying the human limb abnormality congenital talipes equinovarus ('clubfoot') remain incompletely understood. The spontaneous autosomal recessive mouse 'peroneal muscular atrophy' mutant (PMA) is a faithful morphological model of human clubfoot. In PMA mice, the dorsal (peroneal) branches of the sciatic nerves are absent. In this study, the primary developmental defect was identified as a reduced growth of sciatic nerve lateral motor column (LMC) neurons leading to failure to project to dorsal (peroneal) lower limb muscle blocks. The pma mutation was mapped and a candidate gene encoding LIM-domain kinase 1 (Limk1) identified, which is upregulated in mutant lateral LMC motor neurons. Genetic and molecular analyses showed that the mutation acts in the EphA4-Limk1-Cfl1/cofilin-actin pathway to modulate growth cone extension/collapse. In the chicken, both experimental upregulation of Limk1 by electroporation and pharmacological inhibition of actin turnover led to defects in hindlimb spinal motor neuron growth and pathfinding, and mimicked the clubfoot phenotype. The data support a neuromuscular aetiology for clubfoot and provide a mechanistic framework to understand clubfoot in humans.
Assuntos
Doença de Charcot-Marie-Tooth/embriologia , Pé Torto Equinovaro/embriologia , Pé Torto Equinovaro/genética , Quinases Lim/genética , Mutação , Animais , Axônios , Doença de Charcot-Marie-Tooth/genética , Doença de Charcot-Marie-Tooth/patologia , Embrião de Galinha , Mapeamento Cromossômico , Pé Torto Equinovaro/patologia , Modelos Animais de Doenças , Feminino , Membro Posterior/anormalidades , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Mutantes , Neurônios Motores/patologia , Músculo Esquelético/anormalidades , Músculo Esquelético/inervação , Nervo Fibular/anormalidades , Fenótipo , Gravidez , Receptor EphA4/deficiência , Receptor EphA4/genética , Nervo Isquiático/anormalidades , Regulação para CimaRESUMO
Cilia are complex microtubule-based organelles essential to a range of processes associated with embryogenesis and tissue homeostasis. Mutations in components of these organelles or those involved in their assembly may result in a diverse set of diseases collectively known as ciliopathies. Accordingly, many cilia-associated proteins have been described, while those distinguishing cilia subtypes are poorly defined. Here we set out to define genes associated with motile cilia in humans based on their transcriptional signature. To define the signature, we performed network deconvolution of transcriptomics data derived from tissues possessing motile ciliated cell populations. For each tissue, genes coexpressed with the motile cilia-associated transcriptional factor, FOXJ1, were identified. The consensus across tissues provided a transcriptional signature of 248 genes. To validate these, we examined the literature, databases (CilDB, CentrosomeDB, CiliaCarta and SysCilia), single cell RNA-Seq data, and the localisation of mRNA and proteins in motile ciliated cells. In the case of six poorly characterised signature genes, we performed new localisation experiments on ARMC3, EFCAB6, FAM183A, MYCBPAP, RIBC2 and VWA3A. In summary, we report a set of motile cilia-associated genes that helps shape our understanding of these complex cellular organelles.
Assuntos
Cílios/genética , Fatores de Transcrição Forkhead/genética , Transcrição Gênica/genética , Proteínas do Domínio Armadillo , Proteínas de Ligação ao Cálcio , Proteínas de Transporte , Cílios/fisiologia , Expressão Gênica , Humanos , Proteínas de Membrana , Proteínas RepressorasRESUMO
TALPID3 (KIAA0586) is a centrosomal protein which has specific functions during centriole maturation during the formation of the centrosomal-dependent organelle, the cilia, as well as less well understood roles in the cytoskeleton and during cell polarisation. Cilia are an essential component of signal transduction during embryonic development and the loss of TALPID3 function in humans can cause both severe lethal and mild cilia-related developmental disorders known as 'ciliopathies' the most common being Joubert syndrome. TALPID3 related ciliopathies affect the development of multiple organ systems including the brain, skeleton, eyes, lungs and liver. The consequences of TALPID3 dysfunction outside of the cilia and the implications for human diseases are less well understood.
Assuntos
Anormalidades Múltiplas/genética , Proteínas de Ciclo Celular/genética , Doenças Cerebelares/genética , Ciliopatias/genética , Desenvolvimento Embrionário/genética , Regulação da Expressão Gênica no Desenvolvimento , Hipotonia Muscular/genética , Transtornos da Motilidade Ocular/genética , Animais , Ciliopatias/embriologia , HumanosRESUMO
Joubert syndrome (JBTS) is a severe recessive neurodevelopmental ciliopathy which can affect several organ systems. Mutations in known JBTS genes account for approximately half of the cases. By homozygosity mapping and whole-exome sequencing, we identified a novel locus, JBTS23, with a homozygous splice site mutation in KIAA0586 (alias TALPID3), a known lethal ciliopathy locus in model organisms. Truncating KIAA0586 mutations were identified in two additional patients with JBTS. One mutation, c.428delG (p.Arg143Lysfs*4), is unexpectedly common in the general population and may be a major contributor to JBTS. We demonstrate KIAA0586 protein localization at the basal body in human and mouse photoreceptors, as is common for JBTS proteins, and also in pericentriolar locations. We show that loss of TALPID3 (KIAA0586) function in animal models causes abnormal tissue polarity, centrosome length and orientation, and centriolar satellites. We propose that JBTS and other ciliopathies may in part result from cell polarity defects.