RESUMEN
The evolutionarily conserved cohesin complex was originally described for its role in regulating sister-chromatid cohesion during mitosis and meiosis. Cohesin and its regulatory proteins have been implicated in several human developmental disorders, including Cornelia de Lange (CdLS) and Roberts syndromes. Here we show that human mutations in the integral cohesin structural protein RAD21 result in a congenital phenotype consistent with a "cohesinopathy." Children with RAD21 mutations display growth retardation, minor skeletal anomalies, and facial features that overlap findings in individuals with CdLS. Notably, unlike children with mutations in NIPBL, SMC1A, or SMC3, these individuals have much milder cognitive impairment than those with classical CdLS. Mechanistically, these mutations act at the RAD21 interface with the other cohesin proteins STAG2 and SMC1A, impair cellular DNA damage response, and disrupt transcription in a zebrafish model. Our data suggest that, compared to loss-of-function mutations, dominant missense mutations result in more severe functional defects and cause worse structural and cognitive clinical findings. These results underscore the essential role of RAD21 in eukaryotes and emphasize the need for further understanding of the role of cohesin in human development.
Asunto(s)
Proteínas de Ciclo Celular/genética , Proteínas Cromosómicas no Histona/genética , Mutación , Proteínas Nucleares/genética , Fosfoproteínas/genética , Animales , Línea Celular , Supervivencia Celular , Trastornos del Conocimiento/genética , Ensayo Cometa/métodos , Anomalías Craneofaciales/genética , Daño del ADN , Proteínas de Unión al ADN , Síndrome de Cornelia de Lange/genética , Ectromelia/genética , Dosificación de Gen , Genoma Humano , Humanos , Hipertelorismo/genética , Pruebas de Micronúcleos , Mutación Missense , Intercambio de Cromátides Hermanas , Técnicas del Sistema de Dos Híbridos , Pez Cebra , CohesinasRESUMEN
Cornelia de Lange syndrome (CdLS; or Brachmann-de Lange syndrome) is a dominantly inherited congenital malformation disorder with features that include characteristic facies, cognitive delays, growth retardation and limb anomalies. Mutations in nearly 60% of CdLS patients have been identified in NIPBL, which encodes a regulator of the sister chromatid cohesion complex. NIPBL, also known as delangin, is a homolog of yeast and amphibian Scc2 and C. elegans PQN-85. Although the exact mechanism of NIPBL function in sister chromatid cohesion is unclear, in vivo yeast and C. elegans experiments and in vitro vertebrate cell experiments have demonstrated that NIPBL/Scc2 functionally interacts with the MAU2/Scc4 protein to initiate loading of cohesin onto chromatin. To test the significance of this model in the clinical setting of CdLS, we fine-mapped the NIBPL-MAU2 interaction domain and tested the functional significance of missense mutations and variants in NIPBL and MAU2 identified in these minimal domains in a cohort of patients with CdLS. We demonstrate that specific novel mutations at the N-terminus of the MAU2-interacting domain of NIBPL result in markedly reduced MAU2 binding, although we appreciate no consistent clinical difference in the small group of patients with these mutations. These data suggest that factors in addition to MAU2 are essential in determining the clinical features and severity of CdLS.
Asunto(s)
Síndrome de Cornelia de Lange/genética , Síndrome de Cornelia de Lange/metabolismo , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Mutación Missense , Proteínas/genética , Proteínas de Ciclo Celular , Proteínas de Unión al ADN , Facies , Humanos , Péptidos y Proteínas de Señalización Intercelular/química , Fenotipo , Unión Proteica/genética , Dominios y Motivos de Interacción de ProteínasRESUMEN
Mutations in the cohesin regulators NIPBL and ESCO2 are causative of the Cornelia de Lange syndrome (CdLS) and Roberts or SC phocomelia syndrome, respectively. Recently, mutations in the cohesin complex structural component SMC1A have been identified in two probands with features of CdLS. Here, we report the identification of a mutation in the gene encoding the complementary subunit of the cohesin heterodimer, SMC3, and 14 additional SMC1A mutations. All mutations are predicted to retain an open reading frame, and no truncating mutations were identified. Structural analysis of the mutant SMC3 and SMC1A proteins indicate that all are likely to produce functional cohesin complexes, but we posit that they may alter their chromosome binding dynamics. Our data indicate that SMC3 and SMC1A mutations (1) contribute to approximately 5% of cases of CdLS, (2) result in a consistently mild phenotype with absence of major structural anomalies typically associated with CdLS, and (3) in some instances, result in a phenotype that approaches that of apparently nonsyndromic mental retardation.