RESUMEN
The proper development of neuronal circuits during neuromorphogenesis and neuronal-network formation is critically dependent on a coordinated and intricate series of molecular and cellular cues and responses. Although the cortical actin cytoskeleton is known to play a key role in neuromorphogenesis, relatively little is known about the specific molecules important for this process. Using linkage analysis and whole-exome sequencing on samples from families from the Amish community of Ohio, we have demonstrated that mutations in KPTN, encoding kaptin, cause a syndrome typified by macrocephaly, neurodevelopmental delay, and seizures. Our immunofluorescence analyses in primary neuronal cell cultures showed that endogenous and GFP-tagged kaptin associates with dynamic actin cytoskeletal structures and that this association is lost upon introduction of the identified mutations. Taken together, our studies have identified kaptin alterations responsible for macrocephaly and neurodevelopmental delay and define kaptin as a molecule crucial for normal human neuromorphogenesis.
Asunto(s)
Discapacidades del Desarrollo/genética , Megalencefalia/genética , Proteínas de Microfilamentos/genética , Mutación , Convulsiones/genética , Citoesqueleto de Actina/metabolismo , Secuencia de Aminoácidos , Femenino , Técnica del Anticuerpo Fluorescente , Ligamiento Genético , Humanos , Masculino , Proteínas de Microfilamentos/metabolismo , Datos de Secuencia Molecular , LinajeRESUMEN
Numerous human disorders, including Cockayne syndrome, UV-sensitive syndrome, xeroderma pigmentosum, and trichothiodystrophy, result from the mutation of genes encoding molecules important for nucleotide excision repair. Here, we describe a syndrome in which the cardinal clinical features include short stature, hearing loss, premature aging, telangiectasia, neurodegeneration, and photosensitivity, resulting from a homozygous missense (p.Ser228Ile) sequence alteration of the proliferating cell nuclear antigen (PCNA). PCNA is a highly conserved sliding clamp protein essential for DNA replication and repair. Due to this fundamental role, mutations in PCNA that profoundly impair protein function would be incompatible with life. Interestingly, while the p.Ser228Ile alteration appeared to have no effect on protein levels or DNA replication, patient cells exhibited marked abnormalities in response to UV irradiation, displaying substantial reductions in both UV survival and RNA synthesis recovery. The p.Ser228Ile change also profoundly altered PCNA's interaction with Flap endonuclease 1 and DNA Ligase 1, DNA metabolism enzymes. Together, our findings detail a mutation of PCNA in humans associated with a neurodegenerative phenotype, displaying clinical and molecular features common to other DNA repair disorders, which we showed to be attributable to a hypomorphic amino acid alteration.
Asunto(s)
Trastornos por Deficiencias en la Reparación del ADN/genética , Proteínas Mutantes/genética , Mutación Missense , Antígeno Nuclear de Célula en Proliferación/genética , Adolescente , Adulto , Envejecimiento Prematuro/genética , Sustitución de Aminoácidos , Niño , Cromosomas Humanos Par 20/genética , Análisis Mutacional de ADN , Trastornos por Deficiencias en la Reparación del ADN/patología , Trastornos por Deficiencias en la Reparación del ADN/fisiopatología , Enanismo/genética , Femenino , Pérdida Auditiva/genética , Homocigoto , Humanos , Masculino , Modelos Moleculares , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Degeneración Nerviosa/genética , Linaje , Fenotipo , Trastornos por Fotosensibilidad/genética , Antígeno Nuclear de Célula en Proliferación/química , Antígeno Nuclear de Célula en Proliferación/metabolismo , Estructura Cuaternaria de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Síndrome , Telangiectasia/genéticaRESUMEN
INTRODUCTION: 'Stenver's' is the standard plain radiograph view to check the electrode position after cochlear implantation. However, a reproducible alignment for intra-individual comparison of electrode position using a true Stenver's alignment is not always straightforward to achieve, particularly for inexperienced radiographers, or on non-compliant children. In addition, two ionizing exposures in two different positions are required for bilateral cochlear implants. AIMS: To assess the efficacy of other, more simple, single-exposure radiographs for the assessment of electrode position. METHODS: Dummy electrodes and receiver units were bilaterally implanted into a cadaver. Plain radiographs in Stenver's views, and plain antero-posterior (AP) midline radiographic single views incorporating both implants were obtained with the tube at a range of angles tilted caudal and cranial to the perpendicular. Five internationally renowned cochlear implant surgeons were each asked if each radiograph gave adequate information for unilateral and for bilateral implants and they were asked to list in order of their favoured top three views. RESULTS: No surgeon thought that a single-exposure Stenver's view was adequate for assessment of the contra-lateral side. Consensus was that all AP views were fit for the purpose, with no preference given between each of the AP views. The ipsi-lateral Stenver's was considered to give better depth of insertion information. CONCLUSION: There is no apparent advantage of caudal and cranial tilt angles over a straight perpendicular AP. A single-view AP radiograph is an alternative to Stenver's view for a post-unilateral and post-simultaneous bilateral cochlear implant check.