RESUMO
Meier-Gorlin syndrome is a rare recessive disorder characterized by a number of distinct tissue-specific developmental defects. Genes encoding members of the origin recognition complex (ORC) and additional proteins essential for DNA replication (CDC6, CDT1, GMNN, CDC45, MCM5, and DONSON) are mutated in individuals diagnosed with MGS. The essential role of ORC is to license origins during the G1 phase of the cell cycle, but ORC has also been implicated in several nonreplicative functions. Because of its essential role in DNA replication, ORC is required for every cell division during development. Thus, it is unclear how the Meier-Gorlin syndrome mutations in genes encoding ORC lead to the tissue-specific defects associated with the disease. To begin to address these issues, we used Cas9-mediated genome engineering to generate a Drosophila melanogaster model of individuals carrying a specific Meier-Gorlin syndrome mutation in ORC4 along with control strains. Together these strains provide the first metazoan model for an MGS mutation in which the mutation was engineered at the endogenous locus along with precisely defined control strains. Flies homozygous for the engineered MGS allele reach adulthood, but with several tissue-specific defects. Genetic analysis revealed that this Orc4 allele was a hypomorph. Mutant females were sterile, and phenotypic analyses suggested that defects in DNA replication was an underlying cause. By leveraging the well-studied Drosophila system, we provide evidence that a disease-causing mutation in Orc4 disrupts DNA replication, and we propose that in individuals with MGS defects arise preferentially in tissues with a high-replication demand.
Assuntos
Microtia Congênita/genética , Replicação do DNA/genética , Proteínas de Drosophila/genética , Transtornos do Crescimento/genética , Micrognatismo/genética , Complexo de Reconhecimento de Origem/genética , Patela/anormalidades , Alelos , Sequência de Aminoácidos/genética , Animais , Ciclo Celular/genética , Microtia Congênita/fisiopatologia , DNA/genética , Replicação do DNA/fisiologia , Modelos Animais de Doenças , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Feminino , Transtornos do Crescimento/fisiopatologia , Masculino , Micrognatismo/fisiopatologia , Mutação/genética , Especificidade de Órgãos/genética , Complexo de Reconhecimento de Origem/metabolismo , Patela/fisiopatologiaRESUMO
BACKGROUND: Sufentanil is a potent opioid uncommonly used to manage pain and is rarely administered via an intrathecal pain pump system. CASE PRESENTATION: This case illustrates the use of intrathecal sufentanil in a 50-year-old Caucasian man for the management of chronic pain; however, the intrathecal drug delivery system experienced a malfunction which led to 1/100th output of the correct dosage. Interesting aspects of this case report include the uncommon choice of sufentanil use for an intrathecal drug delivery system, as well as the unusual pharmacokinetics of this drug. Specifically, this patient did not experience the major withdrawal that would be expected given significant under dosing of opioid, and this may be explained by the lipophilicity and context-sensitive half-times of sufentanil. CONCLUSIONS: Because of the absence of a clinically significant withdrawal in this case report, clinicians must be aware of relevant pharmacokinetic properties and unusual intrathecal drug delivery system technologies that influence a patient's response when device malfunction occurs.